Merge GCC frontend into the branch

.gitignore

@@ -3,3 +3,5 @@
 
 /doc/*.html
 /doc/*.pdf
+
+a.out

COPYING3

@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
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+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<http://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<http://www.gnu.org/philosophy/why-not-lgpl.html>.

Rakefile

@@ -15,6 +15,7 @@ STAGES = Dir.glob('boot/stage*')
 
 CLEAN.include 'build/boot', 'build/valid'
 CLEAN.include 'doc/*.pdf'
+CLOBBER.include 'build'
 
 def compile(*arguments)
   sh(ENV.fetch('CC', 'gcc'), '-fpie', '-g', *arguments)

config-lang.in

@@ -0,0 +1,21 @@
+# Top level configure fragment for gcc Elna frontend.
+# Copyright (C) 2025 Free Software Foundation, Inc.
+
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+language="elna"
+gcc_subdir="elna/gcc"
+
+. ${srcdir}/elna/gcc/config-lang.in

frontend/dependency.cc

@@ -0,0 +1,102 @@
+/* Dependency graph analysis.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/frontend/dependency.h"
+
+#include <fstream>
+#include <sstream>
+#include <string.h>
+
+#include "elna/frontend/driver.h"
+#include "elna/frontend/semantic.h"
+#include "parser.hh"
+
+namespace elna::frontend
+{
+    dependency::dependency(const char *path)
+        : error_container(path)
+    {
+    }
+
+    dependency read_source(std::istream& entry_point, const char *entry_path)
+    {
+        driver parse_driver{ entry_path };
+        lexer tokenizer(entry_point);
+        yy::parser parser(tokenizer, parse_driver);
+
+        dependency outcome{ entry_path };
+        if (parser())
+        {
+            std::swap(outcome.errors(), parse_driver.errors());
+            return outcome;
+        }
+        else
+        {
+            std::swap(outcome.tree, parse_driver.tree);
+        }
+        declaration_visitor declaration_visitor(entry_path);
+        outcome.tree->accept(&declaration_visitor);
+
+        if (!declaration_visitor.errors().empty())
+        {
+            std::swap(outcome.errors(), declaration_visitor.errors());
+        }
+        outcome.unresolved = declaration_visitor.unresolved;
+
+        return outcome;
+    }
+
+    error_list analyze_semantics(const char *path, std::unique_ptr<unit>& tree, symbol_bag bag)
+    {
+        name_analysis_visitor name_analyser(path, bag);
+        tree->accept(&name_analyser);
+
+        if (name_analyser.has_errors())
+        {
+            return std::move(name_analyser.errors());
+        }
+        type_analysis_visitor type_analyzer(path, bag);
+        tree->accept(&type_analyzer);
+
+        if (type_analyzer.has_errors())
+        {
+            return std::move(type_analyzer.errors());
+        }
+        return error_list{};
+    }
+
+    std::filesystem::path build_path(const std::vector<std::string>& segments)
+    {
+        std::filesystem::path result;
+        std::vector<std::string>::const_iterator segment_iterator = std::cbegin(segments);
+
+        if (segment_iterator == std::cend(segments))
+        {
+            return result;
+        }
+        result = *segment_iterator;
+
+        ++segment_iterator;
+        for (; segment_iterator != std::cend(segments); ++segment_iterator)
+        {
+            result /= *segment_iterator;
+        }
+        result.replace_extension(".elna");
+
+        return result;
+    }
+}

frontend/driver.cc

@@ -0,0 +1,124 @@
+/* Parsing driver.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/frontend/driver.h"
+
+namespace elna::frontend
+{
+    position make_position(const yy::location& location)
+    {
+        position result;
+        result.line = static_cast<std::size_t>(location.begin.line);
+        result.column = static_cast<std::size_t>(location.begin.column);
+
+        return result;
+    }
+
+    syntax_error::syntax_error(const std::string& message,
+            const char *input_file, const yy::location& location)
+        : error(input_file, make_position(location)), message(message)
+    {
+    }
+
+    std::string syntax_error::what() const
+    {
+        return message;
+    }
+
+    driver::driver(const char *input_file)
+        : error_container(input_file)
+    {
+    }
+
+    char escape_char(char escape)
+    {
+        switch (escape)
+        {
+        case 'n':
+            return '\n';
+        case 'a':
+            return '\a';
+        case 'b':
+            return '\b';
+        case 't':
+            return '\t';
+        case 'f':
+            return '\f';
+        case 'r':
+            return '\r';
+        case 'v':
+            return '\v';
+        case '\\':
+            return '\\';
+        case '\'':
+            return '\'';
+        case '"':
+            return '"';
+        case '?':
+            return '\?';
+        case '0':
+            return '\0';
+        default:
+            return escape_invalid_char;
+        }
+    }
+
+    std::optional<std::string> escape_string(const char *escape)
+    {
+        std::string result;
+        const char *current_position = escape + 1;
+
+        while (*current_position != '\0')
+        {
+            if (*current_position == '\\' && *(current_position + 1) == 'x')
+            {
+                current_position += 2;
+
+                std::size_t processed;
+                char character = static_cast<char>(std::stoi(current_position, &processed, 16));
+                if (processed == 0)
+                {
+                    return std::nullopt;
+                }
+                else
+                {
+                    current_position += processed - 1;
+                    result.push_back(character);
+                }
+            }
+            else if (*current_position == '\\')
+            {
+                ++current_position;
+
+                char escape = escape_char(*current_position);
+                if (escape == escape_invalid_char)
+                {
+                    return std::nullopt;
+                }
+                result.push_back(escape);
+            }
+            else
+            {
+                result.push_back(*current_position);
+            }
+            ++current_position;
+        }
+        result.pop_back(); // Remove the terminating quote character.
+
+        return result;
+    }
+}

frontend/lexer.ll

@@ -0,0 +1,320 @@
+/* Lexical analyzer.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+%{
+#define YY_NO_UNISTD_H
+#define YY_USER_ACTION this->location.columns(yyleng);
+
+#include <sstream>
+#include "parser.hh"
+
+#undef YY_DECL
+#define YY_DECL yy::parser::symbol_type elna::frontend::lexer::lex(driver& driver)
+#define yyterminate() return yy::parser::make_YYEOF(this->location)
+%}
+
+%option c++ noyywrap never-interactive
+%option yyclass="lexer"
+
+%x IN_COMMENT
+
+ID1 [A-Za-z_]
+ID2 [A-Za-z0-9_]
+HIGIT [0-9a-fA-F]
+BIGIT [01]
+
+%%
+%{
+    this->location.step();
+%}
+
+<IN_COMMENT>{
+    \*\) BEGIN(INITIAL);
+    [^*\n]+ ; /* Eat comment in chunks. */
+    \* ; /* Eat the lone star. */
+    \n+ {
+        this->location.lines(yyleng);
+        this->location.step();
+    }
+}
+\(\* BEGIN(IN_COMMENT);
+[ \t\r] {
+    this->location.step();
+}
+\n+ {
+    this->location.lines(yyleng);
+}
+if {
+    return yy::parser::make_IF(this->location);
+}
+then {
+    return yy::parser::make_THEN(this->location);
+}
+else {
+    return yy::parser::make_ELSE(this->location);
+}
+elsif {
+    return yy::parser::make_ELSIF(this->location);
+}
+while {
+    return yy::parser::make_WHILE(this->location);
+}
+do {
+    return yy::parser::make_DO(this->location);
+}
+proc {
+    return yy::parser::make_PROCEDURE(this->location);
+}
+begin {
+    return yy::parser::make_BEGIN_BLOCK(this->location);
+                        }
+end {
+    return yy::parser::make_END_BLOCK(this->location);
+}
+extern {
+    return yy::parser::make_EXTERN(this->location);
+}
+const {
+    return yy::parser::make_CONST(this->location);
+}
+var {
+    return yy::parser::make_VAR(this->location);
+}
+type {
+    return yy::parser::make_TYPE(this->location);
+}
+record {
+    return yy::parser::make_RECORD(this->location);
+}
+union {
+    return yy::parser::make_UNION(this->location);
+}
+true {
+    return yy::parser::make_BOOLEAN(true, this->location);
+}
+false {
+    return yy::parser::make_BOOLEAN(false, this->location);
+}
+nil {
+    return yy::parser::make_NIL(this->location);
+}
+\& {
+    return yy::parser::make_AND(this->location);
+}
+xor {
+    return yy::parser::make_XOR(this->location);
+}
+or {
+    return yy::parser::make_OR(this->location);
+}
+\| {
+    return yy::parser::make_PIPE(this->location);
+}
+\~ {
+    return yy::parser::make_NOT(this->location);
+}
+return {
+    return yy::parser::make_RETURN(this->location);
+}
+module {
+    return yy::parser::make_MODULE(this->location);
+}
+program {
+    return yy::parser::make_PROGRAM(this->location);
+}
+import {
+    return yy::parser::make_IMPORT(this->location);
+}
+cast {
+    return yy::parser::make_CAST(this->location);
+}
+defer {
+    return yy::parser::make_DEFER(this->location);
+}
+case {
+    return yy::parser::make_CASE(this->location);
+}
+of {
+    return yy::parser::make_OF(this->location);
+}
+{ID1}{ID2}* {
+    return yy::parser::make_IDENTIFIER(yytext, this->location);
+}
+#{ID1}{ID2}* {
+    return yy::parser::make_TRAIT(yytext + 1, this->location);
+}
+[[:digit:]]+u {
+    unsigned long result = strtoul(yytext, NULL, 10);
+
+    if (errno == ERANGE)
+    {
+        REJECT;
+    }
+    else
+    {
+        return yy::parser::make_WORD(result, this->location);
+    }
+}
+[[:digit:]]+ {
+    long result = strtol(yytext, NULL, 10);
+
+    if (errno == ERANGE)
+    {
+        REJECT;
+    }
+    else
+    {
+        return yy::parser::make_INTEGER(result, this->location);
+    }
+}
+0x{HIGIT}+ {
+    unsigned long result = strtoul(yytext, NULL, 16);
+
+    if (errno == ERANGE)
+    {
+        REJECT;
+    }
+    else
+    {
+        return yy::parser::make_WORD(result, this->location);
+    }
+}
+0b{BIGIT}+ {
+    unsigned long result = strtoul(yytext, NULL, 2);
+
+    if (errno == ERANGE)
+    {
+        REJECT;
+    }
+    else
+    {
+        return yy::parser::make_WORD(result, this->location);
+    }
+}
+[[:digit:]]+\.[[:digit:]]+ {
+    float result = strtof(yytext, NULL);
+
+    if (errno == ERANGE)
+    {
+        REJECT;
+    }
+    else
+    {
+        return yy::parser::make_FLOAT(result, this->location);
+    }
+}
+'[[:print:]]+' {
+    std::optional<std::string> result = escape_string(yytext);
+    if (!result.has_value() || result.value().size() != 1)
+    {
+        REJECT;
+    }
+    return yy::parser::make_CHARACTER(result.value(), this->location);
+}
+\"[[:print:]]*\" {
+    std::optional<std::string> result = escape_string(yytext);
+    if (!result.has_value())
+    {
+        REJECT;
+    }
+    return yy::parser::make_STRING(result.value(), this->location);
+}
+\( {
+    return yy::parser::make_LEFT_PAREN(this->location);
+}
+\) {
+    return yy::parser::make_RIGHT_PAREN(this->location);
+}
+\[ {
+    return yy::parser::make_LEFT_SQUARE(this->location);
+}
+\] {
+    return yy::parser::make_RIGHT_SQUARE(this->location);
+}
+\<\< {
+    return yy::parser::make_SHIFT_LEFT(this->location);
+}
+\>\> {
+    return yy::parser::make_SHIFT_RIGHT(this->location);
+}
+\>= {
+    return yy::parser::make_GREATER_EQUAL(this->location);
+}
+\<= {
+    return yy::parser::make_LESS_EQUAL(this->location);
+}
+\> {
+    return yy::parser::make_GREATER_THAN(this->location);
+}
+\< {
+    return yy::parser::make_LESS_THAN(this->location);
+}
+\<\> {
+    return yy::parser::make_NOT_EQUAL(this->location);
+}
+= {
+    return yy::parser::make_EQUALS(this->location);
+}
+; {
+    return yy::parser::make_SEMICOLON(this->location);
+}
+\. {
+    return yy::parser::make_DOT(this->location);
+}
+, {
+    return yy::parser::make_COMMA(this->location);
+}
+\+ {
+    return yy::parser::make_PLUS(this->location);
+}
+\-> {
+    return yy::parser::make_ARROW(this->location);
+}
+\- {
+    return yy::parser::make_MINUS(this->location);
+}
+\* {
+    return yy::parser::make_MULTIPLICATION(this->location);
+}
+\/ {
+    return yy::parser::make_DIVISION(this->location);
+}
+% {
+    return yy::parser::make_REMAINDER(this->location);
+}
+:= {
+    return yy::parser::make_ASSIGNMENT(this->location);
+}
+: {
+    return yy::parser::make_COLON(this->location);
+}
+\^ {
+    return yy::parser::make_HAT(this->location);
+}
+@ {
+    return yy::parser::make_AT(this->location);
+}
+! {
+    return yy::parser::make_EXCLAMATION(this->location);
+}
+. {
+    std::stringstream ss;
+
+    ss << "Illegal character 0x" << std::hex << static_cast<unsigned int>(yytext[0]);
+    driver.add_error<syntax_error>(ss.str(), driver.input_file, this->location);
+}
+%%

frontend/parser.yy

@@ -0,0 +1,594 @@
+/* Syntax analyzer.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+%require "3.4"
+%language "c++"
+
+%code {
+    using namespace elna;
+}
+
+%code requires {
+    #include <cstdint>
+    #include <iostream>
+    #include "elna/frontend/driver.h"
+
+    #if !defined(yyFlexLexerOnce)
+        #include <FlexLexer.h>
+    #endif
+
+    namespace elna::frontend
+    {
+    class lexer;
+    }
+}
+
+%code provides {
+    namespace elna::frontend
+    {
+
+    class lexer: public yyFlexLexer
+    {
+    public:
+        yy::location location;
+
+        lexer(std::istream& arg_yyin)
+            : yyFlexLexer(&arg_yyin)
+        {
+        }
+
+        yy::parser::symbol_type lex(driver& driver);
+    };
+
+    }
+}
+
+%define api.token.raw
+%define api.token.constructor
+%define api.value.type variant
+
+%parse-param {elna::frontend::lexer& lexer}
+%param {elna::frontend::driver& driver}
+%locations
+
+%header
+
+%code {
+    #define yylex lexer.lex
+}
+%start program;
+
+%token <std::string> IDENTIFIER
+%token <std::string> TRAIT
+%token <std::int32_t> INTEGER
+%token <std::uint32_t> WORD
+%token <float> FLOAT
+%token <std::string> CHARACTER
+%token <std::string> STRING
+%token <bool> BOOLEAN
+%token LEFT_PAREN "(" RIGHT_PAREN ")" LEFT_SQUARE "[" RIGHT_SQUARE "]"
+%token ASSIGNMENT ":="
+    ARROW "->" EXCLAMATION "!"
+    AT "@" HAT "^"
+    COLON ":" SEMICOLON ";" DOT "." COMMA ","
+%token NOT "~"
+    CAST "cast"
+    NIL "nil"
+    CONST "const"
+    VAR "var"
+    PROCEDURE "proc"
+    TYPE "type"
+    RECORD "record"
+    UNION "union"
+    EXTERN "extern"
+    IF "if"
+    WHILE "while"
+    DO "do"
+    THEN "then"
+    ELSE "else"
+    ELSIF "elsif"
+    RETURN "return"
+    PROGRAM "program"
+    MODULE "module"
+    IMPORT "import"
+    BEGIN_BLOCK "begin"
+    END_BLOCK "end"
+    DEFER "defer"
+    CASE "case"
+    OF "of"
+    PIPE "|"
+%token OR "or" AND "&" XOR "xor"
+    EQUALS "=" NOT_EQUAL "<>" LESS_THAN "<" GREATER_THAN ">" LESS_EQUAL "<=" GREATER_EQUAL ">="
+    SHIFT_LEFT "<<" SHIFT_RIGHT ">>"
+    PLUS "+" MINUS "-"
+    MULTIPLICATION "*" DIVISION "/" REMAINDER "%"
+
+%left "or" "&" "xor"
+%left "=" "<>" "<" ">" "<=" ">="
+%left "<<" ">>"
+%left "+" "-"
+%left "*" "/" "%"
+
+%type <elna::frontend::literal_expression *> literal;
+%type <std::vector<elna::frontend::expression *>> case_labels;
+%type <elna::frontend::switch_case> switch_case;
+%type <std::vector<elna::frontend::switch_case>> switch_cases;
+%type <elna::frontend::constant_declaration *> constant_declaration;
+%type <std::vector<elna::frontend::constant_declaration *>> constant_part constant_declarations;
+%type <elna::frontend::variable_declaration *> variable_declaration;
+%type <std::vector<elna::frontend::variable_declaration *>> variable_declarations variable_part;
+%type <elna::frontend::type_expression *> type_expression;
+%type <std::vector<elna::frontend::type_expression *>> type_expressions;
+%type <elna::frontend::traits_expression *> traits_expression;
+%type <elna::frontend::expression *> expression operand simple_expression;
+%type <elna::frontend::unary_expression *> unary_expression;
+%type <elna::frontend::binary_expression *> binary_expression;
+%type <std::vector<elna::frontend::expression *>> expressions actual_parameter_list;
+%type <elna::frontend::designator_expression *> designator_expression;
+%type <elna::frontend::procedure_call*> call_expression;
+%type <elna::frontend::return_statement *> return_statement;
+%type <elna::frontend::statement *> statement;
+%type <std::vector<elna::frontend::statement *>> required_statements optional_statements statement_part;
+%type <elna::frontend::procedure_declaration *> procedure_declaration;
+%type <std::pair<std::vector<std::string>, elna::frontend::procedure_type_expression *>> procedure_heading;
+%type <elna::frontend::procedure_type_expression::return_t> return_declaration;
+%type <std::vector<elna::frontend::procedure_declaration *>> procedure_declarations procedure_part;
+%type <elna::frontend::type_declaration *> type_declaration;
+%type <std::vector<elna::frontend::type_declaration *>> type_declarations type_part;
+%type <std::unique_ptr<elna::frontend::block>> block;
+%type <elna::frontend::field_declaration> field_declaration formal_parameter;
+%type <std::vector<std::pair<std::string, elna::frontend::type_expression *>>>
+    optional_fields required_fields formal_parameters formal_parameter_list;
+%type <std::vector<elna::frontend::conditional_statements *>> elsif_then_statements elsif_do_statements;
+%type <std::vector<elna::frontend::statement *> *> else_statements;
+%type <elna::frontend::cast_expression *> cast_expression;
+%type <elna::frontend::identifier_definition> identifier_definition;
+%type <std::vector<elna::frontend::identifier_definition>> identifier_definitions;
+%type <std::vector<std::string>> identifiers import_declaration;
+%type <std::vector<elna::frontend::import_declaration *>> import_declarations import_part;
+%%
+program:
+    "program" ";" import_part constant_part type_part variable_part procedure_part statement_part "end" "."
+        {
+            auto tree = new frontend::program(frontend::make_position(@1));
+
+            std::swap(tree->imports, $3);
+            std::swap(tree->constants, $4);
+            std::swap(tree->types , $5);
+            std::swap(tree->variables, $6);
+            std::swap(tree->procedures, $7);
+            std::swap(tree->body, $8);
+
+            driver.tree.reset(tree);
+        }
+    | "module" ";" import_part constant_part type_part variable_part procedure_part "end" "."
+        {
+            auto tree = new frontend::unit(frontend::make_position(@1));
+
+            std::swap(tree->imports, $3);
+            std::swap(tree->constants, $4);
+            std::swap(tree->types , $5);
+            std::swap(tree->variables, $6);
+            std::swap(tree->procedures, $7);
+
+            driver.tree.reset(tree);
+        }
+block: constant_part variable_part statement_part "end"
+        {
+            $$ = std::make_unique<frontend::block>(std::move($1), std::move($2), std::move($3));
+        }
+statement_part:
+    /* no statements */ {}
+    | "begin" required_statements { std::swap($$, $2); }
+    | return_statement { $$.push_back($1); }
+    | "begin" required_statements ";" return_statement
+        {
+            std::swap($$, $2);
+            $$.push_back($4);
+        }
+identifier_definition:
+    IDENTIFIER "*" { $$ = frontend::identifier_definition{ $1, true }; }
+    | IDENTIFIER { $$ = frontend::identifier_definition{ $1, false }; }
+identifier_definitions:
+    identifier_definition "," identifier_definitions
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), $1);
+        }
+    | identifier_definition { $$.emplace_back(std::move($1)); }
+return_declaration:
+    /* proper procedure */ {}
+    | "->" "!" { $$ = frontend::procedure_type_expression::return_t(std::monostate{}); }
+    | "->" type_expression { $$ = frontend::procedure_type_expression::return_t($2); }
+procedure_heading: formal_parameter_list return_declaration
+        {
+            $$.second = new frontend::procedure_type_expression(frontend::make_position(@1), std::move($2));
+            for (auto& [name, type] : $1)
+            {
+                $$.first.emplace_back(std::move(name));
+                $$.second->parameters.push_back(type);
+            }
+        }
+procedure_declaration:
+    "proc" identifier_definition procedure_heading ";" block ";"
+        {
+            $$ = new frontend::procedure_declaration(frontend::make_position(@1), std::move($2), $3.second, std::move(*$5));
+            std::swap($3.first, $$->parameter_names);
+        }
+    | "proc" identifier_definition procedure_heading ";" "extern" ";"
+        {
+            $$ = new frontend::procedure_declaration(frontend::make_position(@1), std::move($2), $3.second);
+            std::swap($3.first, $$->parameter_names);
+        }
+procedure_declarations:
+    procedure_declaration procedure_declarations
+        {
+            std::swap($$, $2);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | procedure_declaration { $$.emplace_back(std::move($1)); }
+procedure_part:
+    /* no procedure definitions */ {}
+    | procedure_declarations { std::swap($$, $1); }
+call_expression: designator_expression actual_parameter_list
+        {
+            $$ = new frontend::procedure_call(frontend::make_position(@1), $1);
+            std::swap($$->arguments, $2);
+        }
+cast_expression: "cast" "(" expression ":" type_expression ")"
+        { $$ = new frontend::cast_expression(frontend::make_position(@1), $5, $3); }
+elsif_do_statements:
+    "elsif" expression "do" optional_statements elsif_do_statements
+        {
+            frontend::conditional_statements *branch = new frontend::conditional_statements($2, std::move($4));
+            std::swap($5, $$);
+            $$.emplace($$.begin(), branch);
+        }
+    | {}
+else_statements:
+    "else" optional_statements { $$ = new std::vector<frontend::statement *>(std::move($2)); }
+    | { $$ = nullptr; }
+elsif_then_statements:
+    "elsif" expression "then" optional_statements elsif_then_statements
+        {
+            frontend::conditional_statements *branch = new frontend::conditional_statements($2, std::move($4));
+            std::swap($5, $$);
+            $$.emplace($$.begin(), branch);
+        }
+    | {}
+return_statement: "return" expression
+        { $$ = new frontend::return_statement(frontend::make_position(@1), $2); }
+literal:
+    INTEGER { $$ = new frontend::literal<std::int32_t>(frontend::make_position(@1), $1); }
+    | WORD { $$ = new frontend::literal<std::uint32_t>(frontend::make_position(@1), $1); }
+    | FLOAT { $$ = new frontend::literal<double>(frontend::make_position(@1), $1); }
+    | BOOLEAN { $$ = new frontend::literal<bool>(frontend::make_position(@1), $1); }
+    | CHARACTER { $$ = new frontend::literal<unsigned char>(frontend::make_position(@1), $1.at(0)); }
+    | "nil" { $$ = new frontend::literal<std::nullptr_t>(frontend::make_position(@1), nullptr); }
+    | STRING { $$ = new frontend::literal<std::string>(frontend::make_position(@1), $1); }
+traits_expression:
+    TRAIT "(" type_expressions ")"
+        {
+            $$ = new frontend::traits_expression(frontend::make_position(@1), $1);
+            std::swap($3, $$->parameters);
+        }
+simple_expression:
+    literal { $$ = $1; }
+    | designator_expression { $$ = $1; }
+    | traits_expression { $$ = $1; }
+    | cast_expression { $$ = $1; }
+    | call_expression { $$ = $1; }
+    | "(" expression ")" { $$ = $2; }
+operand:
+    unary_expression { $$ = $1; }
+    | simple_expression { $$ = $1; }
+expression:
+    binary_expression { $$ = $1; }
+    | operand { $$ = $1; }
+binary_expression:
+    expression "*" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::multiplication);
+        }
+    | expression "/" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::division);
+        }
+    | expression "%" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::remainder);
+        }
+    | expression "+" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::sum);
+        }
+    | expression "-" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::subtraction);
+        }
+    | expression "=" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::equals);
+        }
+    | expression "<>" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::not_equals);
+        }
+    | expression "<" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::less);
+        }
+    | expression ">" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::greater);
+        }
+    | expression "<=" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3,
+                frontend::binary_operator::less_equal);
+        }
+    | expression ">=" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::greater_equal);
+        }
+    | expression "&" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::conjunction);
+        }
+    | expression "or" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::disjunction);
+        }
+    | expression "xor" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3,
+                    frontend::binary_operator::exclusive_disjunction);
+        }
+    | expression "<<" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::shift_left);
+        }
+    | expression ">>" expression
+        {
+            $$ = new frontend::binary_expression(frontend::make_position(@2), $1, $3, frontend::binary_operator::shift_right);
+        }
+unary_expression:
+    "@" operand
+        {
+            $$ = new frontend::unary_expression(frontend::make_position(@1), $2, frontend::unary_operator::reference);
+        }
+    | "~" operand
+        {
+            $$ = new frontend::unary_expression(frontend::make_position(@1), $2, frontend::unary_operator::negation);
+        }
+    | "-" operand
+        {
+            $$ = new frontend::unary_expression(frontend::make_position(@1), $2, frontend::unary_operator::minus);
+        }
+expressions:
+    expression "," expressions
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), $1);
+        }
+    | expression { $$.push_back($1); }
+type_expressions:
+    type_expression "," type_expressions
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), $1);
+        }
+    | type_expression { $$.push_back($1); }
+designator_expression:
+    simple_expression "[" expression "]"
+        { $$ = new frontend::array_access_expression(frontend::make_position(@2), $1, $3); }
+    | simple_expression "." IDENTIFIER
+        { $$ = new frontend::field_access_expression(frontend::make_position(@2), $1, $3); }
+    | simple_expression "^"
+        { $$ = new frontend::dereference_expression(frontend::make_position(@1), $1); }
+    | IDENTIFIER
+        { $$ = new frontend::variable_expression(frontend::make_position(@1), $1); }
+statement:
+    designator_expression ":=" expression
+        { $$ = new frontend::assign_statement(frontend::make_position(@1), $1, $3); }
+    | "while" expression "do" optional_statements elsif_do_statements "end"
+        {
+            frontend::conditional_statements *body = new frontend::conditional_statements($2, std::move($4));
+            $$ = new frontend::while_statement(frontend::make_position(@1), body, std::move($5));
+        }
+    | "if" expression "then" optional_statements elsif_then_statements else_statements "end"
+        {
+            frontend::conditional_statements *then = new frontend::conditional_statements($2, std::move($4));
+            $$ = new frontend::if_statement(frontend::make_position(@1), then, std::move($5), $6);
+        }
+    | call_expression { $$ = $1; }
+    | "defer" optional_statements "end"
+        { $$ = new frontend::defer_statement(frontend::make_position(@1), std::move($2)); }
+    | "case" expression "of" switch_cases else_statements "end"
+        { $$ = new frontend::case_statement(frontend::make_position(@1), $2, std::move($4), $5); }
+switch_case: case_labels ":" optional_statements
+        { $$ = { .labels = std::move($1), .statements = std::move($3) }; }
+switch_cases:
+    switch_case "|" switch_cases
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), $1);
+        }
+    | switch_case { $$.push_back($1); }
+case_labels:
+    expression "," case_labels
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), $1);
+        }
+    | expression { $$.push_back($1); }
+required_statements:
+    required_statements ";" statement
+        {
+            std::swap($$, $1);
+            $$.insert($$.cend(), $3);
+        }
+    | statement { $$.push_back($1); }
+optional_statements:
+    required_statements { std::swap($$, $1); }
+    | /* no statements */ {}
+field_declaration:
+    IDENTIFIER ":" type_expression { $$ = std::make_pair($1, $3); }
+required_fields:
+    field_declaration ";" required_fields
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), $1);
+        }
+    | field_declaration { $$.emplace_back($1); }
+optional_fields:
+    required_fields { std::swap($$, $1); }
+    | /* no fields */ {}
+type_expression:
+    "[" INTEGER "]" type_expression
+        {
+            $$ = new frontend::array_type_expression(frontend::make_position(@1), $4, $2);
+        }
+    | "^" type_expression
+        {
+            $$ = new frontend::pointer_type_expression(frontend::make_position(@1), $2);
+        }
+    | "record" optional_fields "end"
+        {
+            $$ = new frontend::record_type_expression(frontend::make_position(@1), std::move($2));
+        }
+    | "union" required_fields "end"
+        {
+            $$ = new frontend::union_type_expression(frontend::make_position(@1), std::move($2));
+        }
+    | "proc" "(" type_expressions ")" return_declaration
+        {
+            auto result = new frontend::procedure_type_expression(frontend::make_position(@1), std::move($5));
+            std::swap(result->parameters, $3);
+            $$ = result;
+        }
+    | "(" identifiers ")"
+        {
+            $$ = new frontend::enumeration_type_expression(frontend::make_position(@1), std::move($2));
+        }
+    | IDENTIFIER
+        {
+            $$ = new frontend::named_type_expression(frontend::make_position(@1), $1);
+        }
+identifiers:
+    IDENTIFIER "," identifiers
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | IDENTIFIER { $$.emplace_back(std::move($1)); }
+variable_declaration:
+    identifier_definitions ":" type_expression ";"
+        {
+            std::shared_ptr<frontend::type_expression> shared_type{ $3 };
+            $$ = new frontend::variable_declaration( frontend::make_position(@2), std::move($1), shared_type);
+        }
+    | identifier_definitions ":" type_expression ":=" "extern" ";"
+        {
+            std::shared_ptr<frontend::type_expression> shared_type{ $3 };
+            $$ = new frontend::variable_declaration( frontend::make_position(@2), std::move($1), shared_type,
+                std::monostate{});
+        }
+    | identifier_definitions ":" type_expression ":=" expression ";"
+        {
+            std::shared_ptr<frontend::type_expression> shared_type{ $3 };
+            $$ = new frontend::variable_declaration( frontend::make_position(@2), std::move($1), shared_type, $5);
+        }
+variable_declarations:
+    /* no variable declarations */ {}
+    | variable_declaration variable_declarations
+        {
+            std::swap($$, $2);
+            $$.insert(std::cbegin($$), $1);
+        }
+variable_part:
+    /* no variable declarations */ {}
+    | "var" variable_declarations { std::swap($$, $2); }
+constant_declaration: identifier_definition ":=" expression ";"
+        {
+            $$ = new frontend::constant_declaration(frontend::make_position(@1), std::move($1), $3);
+        }
+constant_declarations:
+    constant_declaration constant_declarations
+        {
+            std::swap($$, $2);
+            $$.insert(std::cbegin($$), $1);
+        }
+    | /* no constant definitions */ {}
+constant_part:
+    /* no constant definitions */ {}
+    | "const" constant_declarations { std::swap($$, $2); }
+import_declaration:
+    IDENTIFIER "." import_declaration
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | IDENTIFIER { $$.emplace_back(std::move($1)); }
+import_declarations:
+    import_declaration "," import_declarations
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), new frontend::import_declaration(frontend::make_position(@1), std::move($1)));
+        }
+    | import_declaration
+        {
+            $$.emplace_back(new frontend::import_declaration(frontend::make_position(@1), std::move($1)));
+        }
+import_part:
+    /* no import declarations */ {}
+    | "import" import_declarations ";" { std::swap($$, $2); }
+type_declaration: identifier_definition "=" type_expression ";"
+        {
+            $$ = new frontend::type_declaration(frontend::make_position(@1), std::move($1), $3);
+        }
+type_declarations:
+    type_declaration type_declarations
+        {
+            std::swap($$, $2);
+            $$.insert($$.cbegin(), $1);
+        }
+    | /* no type definitions */ {}
+type_part:
+    /* no type definitions */ {}
+    | "type" type_declarations { std::swap($$, $2); }
+formal_parameter:
+    IDENTIFIER ":" type_expression { $$ = std::make_pair($1, $3); }
+formal_parameter_list:
+    "(" ")" {}
+    | "(" formal_parameters ")" { std::swap($$, $2); }
+formal_parameters:
+    formal_parameter "," formal_parameters
+        {
+            std::swap($$, $3);
+            $$.emplace($$.cbegin(), std::move($1));
+        }
+    | formal_parameter { $$.emplace_back(std::move($1)); }
+actual_parameter_list:
+    "(" ")" {}
+    | "(" expressions ")" { std::swap($$, $2); }
+%%
+
+void yy::parser::error(const location_type& loc, const std::string& message)
+{
+    driver.add_error<frontend::syntax_error>(message, driver.input_file, loc);
+}

frontend/result.cc

@@ -0,0 +1,67 @@
+/* Miscellaneous types used across stage boundaries.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/frontend/result.h"
+
+namespace elna::frontend
+{
+    error::error(const char *path, const struct position position)
+        : position(position), path(path)
+    {
+    }
+
+    std::size_t error::line() const noexcept
+    {
+        return this->position.line;
+    }
+
+    std::size_t error::column() const noexcept
+    {
+        return this->position.column;
+    }
+
+    error_container::error_container(const char *input_file)
+        : input_file(input_file)
+    {
+    }
+
+    std::deque<std::unique_ptr<error>>& error_container::errors()
+    {
+        return m_errors;
+    }
+
+    bool error_container::has_errors() const
+    {
+        return !m_errors.empty();
+    }
+
+    bool identifier_definition::operator==(const identifier_definition& that) const
+    {
+        return *this == that.name;
+    }
+
+    bool identifier_definition::operator==(const std::string& that) const
+    {
+        return this->name == that;
+    }
+}
+
+std::size_t std::hash<elna::frontend::identifier_definition>::operator()(
+        const elna::frontend::identifier_definition& key) const
+{
+    return std::hash<std::string>{}(key.name);
+}

frontend/semantic.cc

@@ -0,0 +1,644 @@
+/* Name analysis.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/frontend/semantic.h"
+
+#include <algorithm>
+#include <set>
+
+namespace elna::frontend
+{
+    undeclared_error::undeclared_error(const std::string& identifier, const char *path, const struct position position)
+        : error(path, position), identifier(identifier)
+    {
+    }
+
+    std::string undeclared_error::what() const
+    {
+        return "Type '" + identifier + "' not declared";
+    }
+
+    already_declared_error::already_declared_error(const std::string& identifier,
+            const char *path, const struct position position)
+        : error(path, position), identifier(identifier)
+    {
+    }
+
+    std::string already_declared_error::what() const
+    {
+        return "Symbol '" + identifier + "' has been already declared";
+    }
+
+    field_duplication_error::field_duplication_error(const std::string& field_name,
+            const char *path, const struct position position)
+        : error(path, position), field_name(field_name)
+    {
+    }
+
+    std::string field_duplication_error::what() const
+    {
+        return "Repeated field name '" + field_name + "'";
+    }
+
+    cyclic_declaration_error::cyclic_declaration_error(const std::vector<std::string>& cycle,
+            const char *path, const struct position position)
+        : error(path, position), cycle(cycle)
+    {
+    }
+
+    std::string cyclic_declaration_error::what() const
+    {
+        auto segment = std::cbegin(this->cycle);
+        std::string message = "Type declaration forms a cycle: " + *segment;
+
+        ++segment;
+        for (; segment != std::cend(this->cycle); ++segment)
+        {
+            message += " -> " + *segment;
+        }
+        return message;
+    }
+
+    return_error::return_error(const std::string& identifier, const char *path, const struct position position)
+        : error(path, position), identifier(identifier)
+    {
+    }
+
+    std::string return_error::what() const
+    {
+        return "Procedure '" + identifier + "' is expected to return, but does not have a return statement";
+    }
+
+    variable_initializer_error::variable_initializer_error(const char *path, const struct position position)
+        : error(path, position)
+    {
+    }
+
+    std::string variable_initializer_error::what() const
+    {
+        return "Only one variable can be initialized";
+    }
+
+    type_analysis_visitor::type_analysis_visitor(const char *path, symbol_bag bag)
+        : error_container(path), bag(bag)
+    {
+    }
+
+    void type_analysis_visitor::visit(program *program)
+    {
+        visit(static_cast<unit *>(program));
+    }
+
+    void type_analysis_visitor::visit(procedure_declaration *definition)
+    {
+        if (definition->body.has_value() && definition->heading().return_type.proper_type != nullptr)
+        {
+            for (statement *const statement : definition->body.value().body())
+            {
+                statement->accept(this);
+            }
+            if (!this->returns)
+            {
+                add_error<return_error>(definition->identifier.name, this->input_file, definition->position());
+            }
+        }
+    }
+
+    void type_analysis_visitor::visit(assign_statement *)
+    {
+    }
+
+    void type_analysis_visitor::visit(if_statement *)
+    {
+    }
+
+    void type_analysis_visitor::visit(while_statement *)
+    {
+    }
+
+    void type_analysis_visitor::visit(return_statement *)
+    {
+        this->returns = true;
+    }
+
+    void type_analysis_visitor::visit(defer_statement *)
+    {
+    }
+
+    void type_analysis_visitor::visit(case_statement *)
+    {
+    }
+
+    void type_analysis_visitor::visit(procedure_call *)
+    {
+    }
+
+    bool type_analysis_visitor::check_unresolved_symbol(std::shared_ptr<alias_type> alias,
+            std::vector<std::string>& alias_path)
+    {
+        if (std::find(std::cbegin(alias_path), std::cend(alias_path), alias->name) != std::cend(alias_path))
+        {
+            return false;
+        }
+        alias_path.push_back(alias->name);
+
+        if (auto another_alias = alias->reference.get<alias_type>())
+        {
+            return check_unresolved_symbol(another_alias, alias_path);
+        }
+        return true;
+    }
+
+    void type_analysis_visitor::visit(unit *unit)
+    {
+        for (type_declaration *const type : unit->types)
+        {
+            type->accept(this);
+        }
+        for (procedure_declaration *const procedure : unit->procedures)
+        {
+            this->returns = false;
+            procedure->accept(this);
+        }
+    }
+
+    void type_analysis_visitor::visit(type_declaration *definition)
+    {
+        std::vector<std::string> alias_path;
+        auto unresolved_type = this->bag.lookup(definition->identifier.name)->is_type()->symbol.get<alias_type>();
+
+        if (!check_unresolved_symbol(unresolved_type, alias_path))
+        {
+            add_error<cyclic_declaration_error>(alias_path, this->input_file, definition->position());
+        }
+    }
+
+    name_analysis_visitor::name_analysis_visitor(const char *path, symbol_bag bag)
+        : error_container(path), bag(bag)
+    {
+    }
+
+    procedure_type name_analysis_visitor::build_procedure(procedure_type_expression& type_expression)
+    {
+        procedure_type::return_t result_return;
+
+        if (type_expression.return_type.no_return)
+        {
+            result_return = procedure_type::return_t(std::monostate{});
+        }
+        else if (type_expression.return_type.proper_type != nullptr)
+        {
+            type_expression.return_type.proper_type->accept(this);
+            result_return = procedure_type::return_t(this->current_type);
+        }
+        else
+        {
+            result_return = procedure_type::return_t();
+        }
+        procedure_type result_type = procedure_type(result_return);
+
+        for (struct type_expression *parameter : type_expression.parameters)
+        {
+            parameter->accept(this);
+            result_type.parameters.push_back(this->current_type);
+        }
+        return result_type;
+    }
+
+    void name_analysis_visitor::visit(program *program)
+    {
+        visit(static_cast<unit *>(program));
+
+        for (statement *const statement : program->body)
+        {
+            statement->accept(this);
+        }
+    }
+
+    void name_analysis_visitor::visit(type_declaration *definition)
+    {
+        definition->body().accept(this);
+        auto resolved = this->bag.resolve(definition->identifier.name, this->current_type);
+        auto info = std::make_shared<type_info>(type(resolved));
+
+        info->exported = definition->identifier.exported;
+        this->bag.enter(definition->identifier.name, info);
+    }
+
+    void name_analysis_visitor::visit(named_type_expression *type_expression)
+    {
+        auto unresolved_alias = this->bag.declared(type_expression->name);
+
+        if (unresolved_alias != nullptr)
+        {
+            this->current_type = type(unresolved_alias);
+        }
+        else if (auto from_symbol_table = this->bag.lookup(type_expression->name))
+        {
+            this->current_type = from_symbol_table->is_type()->symbol;
+        }
+        else
+        {
+            add_error<undeclared_error>(type_expression->name, this->input_file, type_expression->position());
+            this->current_type = type();
+        }
+    }
+
+    void name_analysis_visitor::visit(pointer_type_expression *type_expression)
+    {
+        type_expression->base().accept(this);
+        this->current_type = type(std::make_shared<pointer_type>(this->current_type));
+    }
+
+    void name_analysis_visitor::visit(array_type_expression *type_expression)
+    {
+        type_expression->base().accept(this);
+        this->current_type = type(std::make_shared<array_type>(this->current_type, type_expression->size));
+    }
+
+    std::vector<type_field> name_analysis_visitor::build_composite_type(const std::vector<field_declaration>& fields)
+    {
+        std::vector<type_field> result;
+        std::set<std::string> field_names;
+
+        for (auto& field : fields)
+        {
+            if (field_names.find(field.first) != field_names.cend())
+            {
+                add_error<field_duplication_error>(field.first, this->input_file, field.second->position());
+            }
+            else
+            {
+                field_names.insert(field.first);
+                field.second->accept(this);
+                result.push_back(std::make_pair(field.first, this->current_type));
+            }
+        }
+        return result;
+    }
+
+    void name_analysis_visitor::visit(record_type_expression *type_expression)
+    {
+        auto result_type = std::make_shared<record_type>();
+
+        result_type->fields = build_composite_type(type_expression->fields);
+
+        this->current_type = type(result_type);
+    }
+
+    void name_analysis_visitor::visit(union_type_expression *type_expression)
+    {
+        auto result_type = std::make_shared<union_type>();
+
+        result_type->fields = build_composite_type(type_expression->fields);
+
+        this->current_type = type(result_type);
+    }
+
+    void name_analysis_visitor::visit(procedure_type_expression *type_expression)
+    {
+        std::shared_ptr<procedure_type> result_type =
+            std::make_shared<procedure_type>(std::move(build_procedure(*type_expression)));
+
+        this->current_type = type(result_type);
+    }
+
+    void name_analysis_visitor::visit(enumeration_type_expression *type_expression)
+    {
+        std::shared_ptr<enumeration_type> result_type = std::make_shared<enumeration_type>(type_expression->members);
+
+        this->current_type = type(result_type);
+    }
+
+    void name_analysis_visitor::visit(variable_declaration *declaration)
+    {
+        declaration->variable_type().accept(this);
+
+        for (const auto& variable_identifier : declaration->identifiers)
+        {
+            auto variable_symbol = std::make_shared<variable_info>(this->current_type, declaration->is_extern);
+
+            variable_symbol->exported = variable_identifier.exported;
+            if (!this->bag.enter(variable_identifier.name, variable_symbol))
+            {
+                add_error<already_declared_error>(variable_identifier.name, this->input_file,
+                        declaration->position());
+            }
+        }
+    }
+
+    void name_analysis_visitor::visit(constant_declaration *definition)
+    {
+        definition->body().accept(this);
+        auto constant_symbol = std::make_shared<constant_info>(this->current_literal);
+
+        constant_symbol->exported = definition->identifier.exported;
+        this->bag.enter(definition->identifier.name, constant_symbol);
+    }
+
+    void name_analysis_visitor::visit(procedure_declaration *definition)
+    {
+        std::shared_ptr<procedure_info> info;
+        auto heading = build_procedure(definition->heading());
+
+        if (definition->body.has_value())
+        {
+            info = std::make_shared<procedure_info>(heading, definition->parameter_names, this->bag.enter());
+
+            for (constant_declaration *const constant : definition->body.value().constants())
+            {
+                constant->accept(this);
+            }
+            for (variable_declaration *const variable : definition->body.value().variables())
+            {
+                variable->accept(this);
+            }
+            for (statement *const statement : definition->body.value().body())
+            {
+                statement->accept(this);
+            }
+            this->bag.leave();
+        }
+        else
+        {
+            info = std::make_shared<procedure_info>(heading, definition->parameter_names);
+        }
+        info->exported = definition->identifier.exported;
+        this->bag.enter(definition->identifier.name, info);
+    }
+
+    void name_analysis_visitor::visit(assign_statement *statement)
+    {
+        statement->lvalue().accept(this);
+        statement->rvalue().accept(this);
+    }
+
+    void name_analysis_visitor::visit(if_statement *statement)
+    {
+        statement->body().prerequisite().accept(this);
+        for (struct statement *const statement : statement->body().statements)
+        {
+            statement->accept(this);
+        }
+        for (const auto branch : statement->branches)
+        {
+            branch->prerequisite().accept(this);
+
+            for (struct statement *const statement : branch->statements)
+            {
+                statement->accept(this);
+            }
+        }
+        if (statement->alternative != nullptr)
+        {
+            for (struct statement *const statement : *statement->alternative)
+            {
+                statement->accept(this);
+            }
+        }
+    }
+
+    void name_analysis_visitor::visit(import_declaration *)
+    {
+    }
+
+    void name_analysis_visitor::visit(while_statement *statement)
+    {
+        statement->body().prerequisite().accept(this);
+        for (struct statement *const statement : statement->body().statements)
+        {
+            statement->accept(this);
+        }
+        for (const auto branch : statement->branches)
+        {
+            branch->prerequisite().accept(this);
+
+            for (struct statement *const statement : branch->statements)
+            {
+                statement->accept(this);
+            }
+        }
+    }
+
+    void name_analysis_visitor::visit(return_statement *statement)
+    {
+        statement->return_expression().accept(this);
+    }
+
+    void name_analysis_visitor::visit(defer_statement *statement)
+    {
+        for (struct statement *const statement : statement->statements)
+        {
+            statement->accept(this);
+        }
+    }
+
+    void name_analysis_visitor::visit(case_statement *statement)
+    {
+        statement->condition().accept(this);
+        for (const switch_case& case_block : statement->cases)
+        {
+            for (expression *const case_label : case_block.labels)
+            {
+                case_label->accept(this);
+            }
+            for (struct statement *const statement : case_block.statements)
+            {
+                statement->accept(this);
+            }
+        }
+        if (statement->alternative != nullptr)
+        {
+            for (struct statement *const statement : *statement->alternative)
+            {
+                statement->accept(this);
+            }
+        }
+    }
+
+    void name_analysis_visitor::visit(procedure_call *call)
+    {
+        call->callable().accept(this);
+        for (expression *const argument: call->arguments)
+        {
+            argument->accept(this);
+        }
+    }
+
+    void name_analysis_visitor::visit(unit *unit)
+    {
+        for (type_declaration *const type : unit->types)
+        {
+            type->accept(this);
+        }
+        for (variable_declaration *const variable : unit->variables)
+        {
+            variable->accept(this);
+        }
+        for (procedure_declaration *const procedure : unit->procedures)
+        {
+            procedure->accept(this);
+        }
+    }
+
+    void name_analysis_visitor::visit(traits_expression *trait)
+    {
+        if (!trait->parameters.empty())
+        {
+            trait->parameters.front()->accept(this);
+            trait->types.push_back(this->current_type);
+        }
+    }
+
+    void name_analysis_visitor::visit(cast_expression *expression)
+    {
+        expression->value().accept(this);
+        expression->target().accept(this);
+        expression->expression_type = this->current_type;
+    }
+
+    void name_analysis_visitor::visit(binary_expression *expression)
+    {
+        expression->lhs().accept(this);
+        expression->rhs().accept(this);
+    }
+
+    void name_analysis_visitor::visit(unary_expression *expression)
+    {
+        expression->operand().accept(this);
+    }
+
+    void name_analysis_visitor::visit(variable_expression *)
+    {
+    }
+
+    void name_analysis_visitor::visit(array_access_expression *expression)
+    {
+        expression->base().accept(this);
+        expression->index().accept(this);
+    }
+
+    void name_analysis_visitor::visit(field_access_expression *expression)
+    {
+        expression->base().accept(this);
+    }
+
+    void name_analysis_visitor::visit(dereference_expression *expression)
+    {
+        expression->base().accept(this);
+    }
+
+    void name_analysis_visitor::visit(literal<std::int32_t> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    void name_analysis_visitor::visit(literal<std::uint32_t> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    void name_analysis_visitor::visit(literal<double> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    void name_analysis_visitor::visit(literal<bool> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    void name_analysis_visitor::visit(literal<unsigned char> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    void name_analysis_visitor::visit(literal<std::nullptr_t> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    void name_analysis_visitor::visit(literal<std::string> *literal)
+    {
+        this->current_literal = literal->value;
+    }
+
+    declaration_visitor::declaration_visitor(const char *path)
+        : error_container(path)
+    {
+    }
+
+    void declaration_visitor::visit(program *program)
+    {
+        visit(static_cast<unit *>(program));
+    }
+
+    void declaration_visitor::visit(import_declaration *)
+    {
+    }
+
+    void declaration_visitor::visit(unit *unit)
+    {
+        for (import_declaration *const _import : unit->imports)
+        {
+            _import->accept(this);
+        }
+        for (type_declaration *const type : unit->types)
+        {
+            type->accept(this);
+        }
+        for (variable_declaration *const variable : unit->variables)
+        {
+            variable->accept(this);
+        }
+        for (procedure_declaration *const procedure : unit->procedures)
+        {
+            procedure->accept(this);
+        }
+    }
+
+    void declaration_visitor::visit(type_declaration *definition)
+    {
+        const std::string& type_identifier = definition->identifier.name;
+
+        if (!this->unresolved.insert({ type_identifier, std::make_shared<alias_type>(type_identifier) }).second)
+        {
+            add_error<already_declared_error>(definition->identifier.name, this->input_file,
+                    definition->position());
+        }
+    }
+
+    void declaration_visitor::visit(variable_declaration *declaration)
+    {
+        if (declaration->has_initializer() && declaration->identifiers.size() > 1)
+        {
+            add_error<variable_initializer_error>(this->input_file, declaration->position());
+        }
+    }
+
+    void declaration_visitor::visit(procedure_declaration *definition)
+    {
+        if (!definition->body.has_value())
+        {
+            return;
+        }
+        for (variable_declaration *const variable : definition->body.value().variables())
+        {
+            variable->accept(this);
+        }
+    }
+}

frontend/symbol.cc

@@ -0,0 +1,427 @@
+/* Symbol definitions.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/frontend/symbol.h"
+
+namespace elna::frontend
+{
+    type::type()
+    {
+    }
+
+    type::type(std::shared_ptr<alias_type> alias)
+        : tag(type_tag::alias), alias(alias)
+    {
+    }
+
+    type::type(std::shared_ptr<primitive_type> primitive)
+        : tag(type_tag::primitive), primitive(primitive)
+    {
+    }
+
+    type::type(std::shared_ptr<record_type> record)
+        : tag(type_tag::record), record(record)
+    {
+    }
+
+    type::type(std::shared_ptr<union_type> _union)
+        : tag(type_tag::_union), _union(_union)
+    {
+    }
+
+    type::type(std::shared_ptr<pointer_type> pointer)
+        : tag(type_tag::pointer), pointer(pointer)
+    {
+    }
+
+    type::type(std::shared_ptr<array_type> array)
+        : tag(type_tag::array), array(array)
+    {
+    }
+
+    type::type(std::shared_ptr<procedure_type> procedure)
+        : tag(type_tag::procedure), procedure(procedure)
+    {
+    }
+
+    type::type(std::shared_ptr<enumeration_type> enumeration)
+        : tag(type_tag::enumeration), enumeration(enumeration)
+    {
+    }
+
+    void type::copy(const type& other)
+    {
+        switch (other.tag)
+        {
+        case type_tag::empty:
+            break;
+        case type_tag::alias:
+            new (&alias) std::weak_ptr<alias_type>(other.alias);
+            break;
+        case type_tag::primitive:
+            new (&primitive) std::shared_ptr<primitive_type>(other.primitive);
+            break;
+        case type_tag::record:
+            new (&record) std::shared_ptr<record_type>(other.record);
+            break;
+        case type_tag::_union:
+            new (&_union) std::shared_ptr<union_type>(other._union);
+            break;
+        case type_tag::pointer:
+            new (&pointer) std::shared_ptr<pointer_type>(other.pointer);
+            break;
+        case type_tag::array:
+            new (&array) std::shared_ptr<array_type>(other.array);
+            break;
+        case type_tag::procedure:
+            new (&procedure) std::shared_ptr<procedure_type>(other.procedure);
+            break;
+        case type_tag::enumeration:
+            new (&enumeration) std::shared_ptr<enumeration_type>(other.enumeration);
+            break;
+        }
+    }
+
+    type::type(const type& other)
+        : tag(other.tag)
+    {
+        copy(other);
+    }
+
+    void type::move(type&& other)
+    {
+        switch (other.tag)
+        {
+        case type_tag::empty:
+            break;
+        case type_tag::alias:
+            new (&alias) std::weak_ptr<alias_type>(std::move(other.alias));
+            break;
+        case type_tag::primitive:
+            new (&primitive) std::shared_ptr<primitive_type>(std::move(other.primitive));
+            break;
+        case type_tag::record:
+            new (&record) std::shared_ptr<record_type>(std::move(other.record));
+            break;
+        case type_tag::_union:
+            new (&_union) std::shared_ptr<union_type>(std::move(other._union));
+            break;
+        case type_tag::pointer:
+            new (&pointer) std::shared_ptr<pointer_type>(std::move(other.pointer));
+            break;
+        case type_tag::array:
+            new (&array) std::shared_ptr<array_type>(std::move(other.array));
+            break;
+        case type_tag::procedure:
+            new (&procedure) std::shared_ptr<procedure_type>(std::move(other.procedure));
+            break;
+        case type_tag::enumeration:
+            new (&enumeration) std::shared_ptr<enumeration_type>(std::move(other.enumeration));
+            break;
+        }
+    }
+
+    type& type::operator=(const type& other)
+    {
+        this->~type();
+        this->tag = other.tag;
+        copy(other);
+        return *this;
+    }
+
+    type::type(type&& other)
+        : tag(other.tag)
+    {
+        move(std::move(other));
+    }
+
+    type& type::operator=(type&& other)
+    {
+        this->~type();
+        this->tag = other.tag;
+        move(std::move(other));
+        return *this;
+    }
+
+    bool type::operator==(const std::nullptr_t&)
+    {
+        return empty();
+    }
+
+    type::~type()
+    {
+        switch (tag)
+        {
+        case type_tag::empty:
+            break;
+        case type_tag::alias:
+            this->alias.~weak_ptr<alias_type>();
+            break;
+        case type_tag::primitive:
+            this->primitive.~shared_ptr<primitive_type>();
+            break;
+        case type_tag::record:
+            this->record.~shared_ptr<record_type>();
+            break;
+        case type_tag::_union:
+            this->_union.~shared_ptr<union_type>();
+            break;
+        case type_tag::pointer:
+            this->pointer.~shared_ptr<pointer_type>();
+            break;
+        case type_tag::array:
+            this->array.~shared_ptr<array_type>();
+            break;
+        case type_tag::procedure:
+            this->procedure.~shared_ptr<procedure_type>();
+            break;
+        case type_tag::enumeration:
+            this->enumeration.~shared_ptr<enumeration_type>();
+            break;
+        }
+    }
+
+    template<>
+    std::shared_ptr<alias_type> type::get<alias_type>() const
+    {
+        return tag == type_tag::alias ? this->alias.lock() : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<primitive_type> type::get<primitive_type>() const
+    {
+        return tag == type_tag::primitive ? this->primitive : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<record_type> type::get<record_type>() const
+    {
+        return tag == type_tag::record ? this->record : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<union_type> type::get<union_type>() const
+    {
+        return tag == type_tag::_union ? this->_union : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<pointer_type> type::get<pointer_type>() const
+    {
+        return tag == type_tag::pointer ? this->pointer : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<array_type> type::get<array_type>() const
+    {
+        return tag == type_tag::array ? this->array : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<procedure_type> type::get<procedure_type>() const
+    {
+        return tag == type_tag::procedure ? this->procedure : nullptr;
+    }
+
+    template<>
+    std::shared_ptr<enumeration_type> type::get<enumeration_type>() const
+    {
+        return tag == type_tag::enumeration ? this->enumeration : nullptr;
+    }
+
+    bool type::empty() const
+    {
+        return tag == type_tag::empty;
+    }
+
+    alias_type::alias_type(const std::string& name)
+        : name(name), reference()
+    {
+    }
+
+    pointer_type::pointer_type(type base)
+        : base(base)
+    {
+    }
+
+    array_type::array_type(type base, std::uint64_t size)
+        : base(base), size(size)
+    {
+    }
+
+    primitive_type::primitive_type(const std::string& identifier)
+        : identifier(identifier)
+    {
+    }
+
+    procedure_type::procedure_type(return_t return_type)
+        : return_type(return_type)
+    {
+    }
+
+    enumeration_type::enumeration_type(const std::vector<std::string>& members)
+        : members(members)
+    {
+    }
+
+    info::~info()
+    {
+    }
+
+    std::shared_ptr<type_info> info::is_type()
+    {
+        return nullptr;
+    }
+
+    std::shared_ptr<procedure_info> info::is_procedure()
+    {
+        return nullptr;
+    }
+
+    std::shared_ptr<constant_info> info::is_constant()
+    {
+        return nullptr;
+    }
+
+    std::shared_ptr<variable_info> info::is_variable()
+    {
+        return nullptr;
+    }
+
+    type_info::type_info(const type symbol)
+        : symbol(symbol)
+    {
+    }
+
+    std::shared_ptr<type_info> type_info::is_type()
+    {
+        return std::static_pointer_cast<type_info>(shared_from_this());
+    }
+
+    procedure_info::procedure_info(const procedure_type symbol, const std::vector<std::string> names,
+            std::shared_ptr<symbol_table> scope)
+        : symbol(symbol), names(names), scope(scope)
+    {
+    }
+
+    std::shared_ptr<procedure_info> procedure_info::is_procedure()
+    {
+        return std::static_pointer_cast<procedure_info>(shared_from_this());
+    }
+
+    bool procedure_info::is_extern() const
+    {
+        return this->scope == nullptr;
+    }
+
+    constant_info::constant_info(const variant& symbol)
+        : symbol(symbol)
+    {
+    }
+
+    std::shared_ptr<constant_info> constant_info::is_constant()
+    {
+        return std::static_pointer_cast<constant_info>(shared_from_this());
+    }
+
+    variable_info::variable_info(const type symbol, bool is_extern)
+        : symbol(symbol), is_extern(is_extern)
+    {
+    }
+
+    std::shared_ptr<variable_info> variable_info::is_variable()
+    {
+        return std::static_pointer_cast<variable_info>(shared_from_this());
+    }
+
+    std::shared_ptr<symbol_table> builtin_symbol_table()
+    {
+        auto result = std::make_shared<symbol_table>();
+
+        result->enter("Int", std::make_shared<type_info>(type(std::make_shared<primitive_type>("Int"))));
+        result->enter("Word", std::make_shared<type_info>(type(std::make_shared<primitive_type>("Word"))));
+        result->enter("Char", std::make_shared<type_info>(type(std::make_shared<primitive_type>("Char"))));
+        result->enter("Bool", std::make_shared<type_info>(type(std::make_shared<primitive_type>("Bool"))));
+        result->enter("Pointer", std::make_shared<type_info>(type(std::make_shared<primitive_type>("Pointer"))));
+        result->enter("Float", std::make_shared<type_info>(type(std::make_shared<primitive_type>("Float"))));
+        result->enter("String", std::make_shared<type_info>(type(std::make_shared<primitive_type>("String"))));
+
+        return result;
+    }
+
+    symbol_bag::symbol_bag(forward_table&& unresolved, std::shared_ptr<symbol_table> global_table)
+        : unresolved(unresolved)
+    {
+        this->symbols = std::make_shared<symbol_table>(global_table);
+    }
+
+    std::shared_ptr<info> symbol_bag::lookup(const std::string& name)
+    {
+        for (auto import_bag : this->imports)
+        {
+            if (auto result = import_bag->lookup(name))
+            {
+                return result;
+            }
+        }
+        return this->symbols->lookup(name);
+    }
+
+    bool symbol_bag::enter(const std::string& name, std::shared_ptr<info> entry)
+    {
+        return this->symbols->enter(name, entry);
+    }
+
+    std::shared_ptr<symbol_table> symbol_bag::enter()
+    {
+        this->symbols = std::make_shared<symbol_table>(this->symbols);
+        return this->symbols;
+    }
+
+    void symbol_bag::enter(std::shared_ptr<symbol_table> child)
+    {
+        this->symbols = child;
+    }
+
+    std::shared_ptr<symbol_table> symbol_bag::leave()
+    {
+        std::shared_ptr<symbol_table> result = this->symbols;
+
+        this->symbols = result->scope();
+        return result;
+    }
+
+    std::shared_ptr<alias_type> symbol_bag::declared(const std::string& symbol_name)
+    {
+        auto unresolved_alias = this->unresolved.find(symbol_name);
+
+        return unresolved_alias == this->unresolved.end() ? std::shared_ptr<alias_type>() : unresolved_alias->second;
+    }
+
+    std::shared_ptr<alias_type> symbol_bag::resolve(const std::string& symbol_name, type& resolution)
+    {
+        auto unresolved_declaration = this->unresolved.at(symbol_name);
+
+        unresolved_declaration->reference = resolution;
+        return unresolved_declaration;
+    }
+
+    void symbol_bag::add_import(const symbol_bag& bag)
+    {
+        this->imports.push_front(bag.symbols);
+    }
+}

gcc/Make-lang.in

@@ -0,0 +1,174 @@
+# Top level -*- makefile -*- fragment for the Elna frontend.
+# Copyright (C) 2025 Free Software Foundation, Inc.
+
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+ELNA_INSTALL_NAME := $(shell echo gelna|sed '$(program_transform_name)')
+ELNA_TARGET_INSTALL_NAME := $(target_noncanonical)-$(shell echo gelna|sed '$(program_transform_name)')
+
+elna: elna1$(exeext)
+
+.PHONY: elna
+
+# Driver
+
+ELNA_OBJS = \
+   $(GCC_OBJS) \
+   elna/elna-spec.o \
+   $(END)
+
+gelna$(exeext): $(ELNA_OBJS) $(EXTRA_GCC_OBJS) libcommon-target.a $(LIBDEPS)
+	+$(LINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
+	  $(ELNA_OBJS) $(EXTRA_GCC_OBJS) libcommon-target.a \
+	  $(EXTRA_GCC_LIBS) $(LIBS)
+
+# Create a version of the gelna driver which calls the cross-compiler.
+gelna-cross$(exeext): gelna$(exeext)
+	-rm -f gelna-cross$(exeext)
+	cp gelna$(exeext) gelna-cross$(exeext)
+
+# The compiler proper
+
+elna_OBJS = \
+	elna/elna1.o \
+	elna/elna-generic.o \
+	elna/elna-diagnostic.o \
+	elna/elna-tree.o \
+	elna/elna-builtins.o \
+	elna/ast.o \
+	elna/dependency.o \
+	elna/driver.o \
+	elna/lexer.o \
+	elna/parser.o \
+	elna/semantic.o \
+	elna/symbol.o \
+	elna/result.o \
+	$(END)
+
+elna1$(exeext): attribs.o $(elna_OBJS) $(BACKEND) $(LIBDEPS)
+	+$(LLINKER) $(ALL_LINKERFLAGS) $(LDFLAGS) -o $@ \
+	      attribs.o $(elna_OBJS) $(BACKEND) $(LIBS) $(BACKENDLIBS)
+
+elna.all.cross: gelna-cross$(exeext)
+
+elna.start.encap: gelna$(exeext)
+elna.rest.encap:
+
+# No elna-specific selftests.
+selftest-elna:
+
+ELNA_TEXI_FILES = \
+  elna/gcc/gelna.texi \
+  $(srcdir)/doc/include/fdl.texi \
+  $(srcdir)/doc/include/gpl_v3.texi \
+  $(srcdir)/doc/include/funding.texi \
+  $(srcdir)/doc/include/gcc-common.texi \
+  gcc-vers.texi
+
+elna.install-common: installdirs
+	-rm -f $(DESTDIR)$(bindir)/$(ELNA_INSTALL_NAME)$(exeext)
+	$(INSTALL_PROGRAM) gelna$(exeext) $(DESTDIR)$(bindir)/$(ELNA_INSTALL_NAME)$(exeext)
+	-if test -f elna1$(exeext); then \
+	  if test -f gelna-cross$(exeext); then \
+	    :; \
+	  else \
+	    rm -f $(DESTDIR)$(bindir)/$(ELNA_TARGET_INSTALL_NAME)$(exeext); \
+	    ( cd $(DESTDIR)$(bindir) && \
+          $(LN) $(ELNA_INSTALL_NAME)$(exeext) $(ELNA_TARGET_INSTALL_NAME)$(exeext) ); \
+	  fi; \
+	fi
+
+$(build_htmldir)/gelna/index.html: $(ELNA_TEXI_FILES)
+	$(mkinstalldirs) $(@D)
+	rm -f $(@D)/*
+	$(TEXI2HTML) -I $(gcc_docdir)/include -I $(srcdir)/elna -o $(@D) $<
+
+# Required goals, they still do nothing
+elna.install-man:
+elna.install-info:
+elna.install-pdf:
+elna.install-plugin:
+
+elna.install-html: $(build_htmldir)/gelna
+	@$(NORMAL_INSTALL)
+	test -z "$(htmldir)" || $(mkinstalldirs) "$(DESTDIR)$(htmldir)"
+	@for p in $(build_htmldir)/gelna; do \
+	  if test -f "$$p" || test -d "$$p"; then d=""; else d="$(srcdir)/"; fi; \
+	  f=$(html__strip_dir) \
+	  if test -d "$$d$$p"; then \
+	    echo " $(mkinstalldirs) '$(DESTDIR)$(htmldir)/$$f'"; \
+	    $(mkinstalldirs) "$(DESTDIR)$(htmldir)/$$f" || exit 1; \
+	    echo " $(INSTALL_DATA) '$$d$$p'/* '$(DESTDIR)$(htmldir)/$$f'"; \
+	    $(INSTALL_DATA) "$$d$$p"/* "$(DESTDIR)$(htmldir)/$$f"; \
+	  else \
+	    echo " $(INSTALL_DATA) '$$d$$p' '$(DESTDIR)$(htmldir)/$$f'"; \
+	    $(INSTALL_DATA) "$$d$$p" "$(DESTDIR)$(htmldir)/$$f"; \
+	  fi; \
+	done
+
+elna.info:
+elna.dvi:
+elna.pdf:
+elna.html: $(build_htmldir)/gelna/index.html
+elna.man:
+elna.mostlyclean:
+elna.clean:
+elna.distclean:
+elna.maintainer-clean:
+
+# make uninstall
+elna.uninstall:
+	-rm -f gelna$(exeext) elna1$(exeext)
+	-rm -f $(elna_OBJS)
+
+# Used for handling bootstrap
+elna.stage1: stage1-start
+	-mv elna/*$(objext) stage1/elna
+elna.stage2: stage2-start
+	-mv elna/*$(objext) stage2/elna
+elna.stage3: stage3-start
+	-mv elna/*$(objext) stage3/elna
+elna.stage4: stage4-start
+	-mv elna/*$(objext) stage4/elna
+elna.stageprofile: stageprofile-start
+	-mv elna/*$(objext) stageprofile/elna
+elna.stagefeedback: stagefeedback-start
+	-mv elna/*$(objext) stagefeedback/elna
+
+ELNA_INCLUDES = -I $(srcdir)/elna/include -I elna/generated
+ELNA_CXXFLAGS = -std=c++17
+
+elna/%.o: elna/frontend/%.cc elna/generated/parser.hh elna/generated/location.hh
+	$(COMPILE) $(ELNA_CXXFLAGS) $(ELNA_INCLUDES) $<
+	$(POSTCOMPILE)
+
+elna/%.o: elna/generated/%.cc elna/generated/parser.hh elna/generated/location.hh
+	$(COMPILE) $(ELNA_CXXFLAGS) $(ELNA_INCLUDES) $<
+	$(POSTCOMPILE)
+
+elna/%.o: elna/gcc/%.cc elna/generated/parser.hh elna/generated/location.hh
+	$(COMPILE) $(ELNA_CXXFLAGS) $(ELNA_INCLUDES) $<
+	$(POSTCOMPILE)
+
+elna/generated/parser.cc: elna/frontend/parser.yy
+	mkdir -p $(dir $@)
+	$(BISON) -d -o $@ $<
+
+elna/generated/parser.hh elna/generated/location.hh: elna/generated/parser.cc
+	@touch $@
+
+elna/generated/lexer.cc: elna/frontend/lexer.ll
+	mkdir -p $(dir $@)
+	$(FLEX) -o $@ $<

gcc/README.md

@@ -0,0 +1,42 @@
+# Elna programming language
+
+## Current implementation
+
+This repository contains a GCC frontend for Elna. After finishing the frontend
+I'm planning to rewrite the compiler in Elna itself with its own backend and
+a hand-written parser. So GCC gives a way to have a simple bootstrap compiler
+and a possbility to compile Elna programs for different platforms.
+
+## Grammar
+
+Flex and bison grammar specifications, `lexer.ll` and `parser.yy`, can be found
+in the `boot/` directory.
+
+## Build
+
+The frontend requires GCC 15.2.0 (not tested with other versions).
+
+Download the GCC source. Copy the contents of this repository into `gcc/elna`
+inside GCC. Finally build GCC enabling the frontend with
+`--enable-languages=c,c++,elna`. After the installation the compiler can be
+invoked with `$prefix/bin/gelna`.
+
+There is also a `Rakefile` that downloads, builds and installs GCC into the
+`./build/` subdirectory. The `Rakefile` assumes that ruby and rake, as well as
+all GCC dependencies are already available in the system. It works under Linux
+and Mac OS. In the latter case GCC is patched with the patches used by Homebrew
+(official GCC doesn't support Apple silicon targets). Invoke with
+
+```sh
+rake boot
+```
+
+`gcc` binary is used by default, but a different gcc version can be specified
+by passing `CC` and `CXX` environment variables to rake, e.g.:
+
+```sh
+rake CC=gcc-15 CXX=g++-15 boot
+```
+
+See `rake -T` for more tasks. The GCC source is under `build/tools`. The
+installation path is `build/host/install`.

gcc/config-lang.in

@@ -0,0 +1,37 @@
+# Top level configure fragment for gcc Elna frontend.
+# Copyright (C) 2025 Free Software Foundation, Inc.
+
+# GCC is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3, or (at your option)
+# any later version.
+
+# GCC is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with GCC; see the file COPYING3.  If not see
+# <http://www.gnu.org/licenses/>.
+
+# Configure looks for the existence of this file to auto-config each language.
+# We define several parameters used by configure:
+#
+# language	- name of language as it would appear in $(LANGUAGES)
+# boot_language	- "yes" if we need to build this language in stage1
+# compilers	- value to add to $(COMPILERS)
+
+language="elna"
+gcc_subdir="elna/gcc"
+
+compilers="elna1\$(exeext)"
+
+target_libs=""
+
+gtfiles="\$(srcdir)/elna/gcc/elna1.cc \$(srcdir)/elna/include/elna/gcc/elna1.h"
+
+lang_requires_boot_languages=c++
+
+# Do not build by default
+build_by_default="no"

gcc/elna-builtins.cc

@@ -0,0 +1,274 @@
+/* Builtin definitions.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include <algorithm>
+
+#include "elna/gcc/elna-builtins.h"
+#include "elna/gcc/elna1.h"
+#include "stor-layout.h"
+#include "stringpool.h"
+#include "elna/gcc/elna-tree.h"
+
+namespace elna::gcc
+{
+    void init_ttree()
+    {
+        elna_int_type_node = long_integer_type_node;
+        elna_word_type_node = size_type_node;
+        elna_char_type_node = unsigned_char_type_node;
+        elna_pointer_type_node = ptr_type_node;
+        elna_float_type_node = double_type_node;
+
+        elna_bool_type_node = boolean_type_node;
+        elna_bool_true_node = boolean_true_node;
+        elna_bool_false_node = boolean_false_node;
+
+        elna_pointer_nil_node = null_pointer_node;
+
+        elna_string_type_node = make_node(RECORD_TYPE);
+        tree string_ptr_type = build_pointer_type_for_mode(elna_char_type_node, VOIDmode, true);
+
+        elna_string_length_field_node = build_field(UNKNOWN_LOCATION,
+                elna_string_type_node, "length", build_qualified_type(elna_word_type_node, TYPE_QUAL_CONST));
+        elna_string_ptr_field_node = build_field(UNKNOWN_LOCATION,
+                elna_string_type_node, "ptr", build_qualified_type(string_ptr_type, TYPE_QUAL_CONST));
+
+        TYPE_FIELDS(elna_string_type_node) = chainon(elna_string_ptr_field_node, elna_string_length_field_node);
+        layout_type(elna_string_type_node);
+    }
+
+    static
+    tree declare_builtin_type(std::shared_ptr<symbol_table> symbol_table, const char *name, tree type)
+    {
+        tree identifier = get_identifier(name);
+        tree type_declaration = build_decl(UNKNOWN_LOCATION, TYPE_DECL, identifier, type);
+
+        symbol_table->enter(name, type_declaration);
+
+        return type_declaration;
+    }
+
+    std::shared_ptr<symbol_table> builtin_symbol_table()
+    {
+        std::shared_ptr<elna::gcc::symbol_table> symbol_table = std::make_shared<elna::gcc::symbol_table>();
+
+        declare_builtin_type(symbol_table, "Int", elna_int_type_node);
+        declare_builtin_type(symbol_table, "Word", elna_word_type_node);
+        declare_builtin_type(symbol_table, "Char", elna_char_type_node);
+        declare_builtin_type(symbol_table, "Bool", elna_bool_type_node);
+        declare_builtin_type(symbol_table, "Pointer", elna_pointer_type_node);
+        declare_builtin_type(symbol_table, "Float", elna_float_type_node);
+
+        tree string_declaration = declare_builtin_type(symbol_table, "String", elna_string_type_node);
+        TYPE_NAME(elna_string_type_node) = DECL_NAME(string_declaration);
+        TYPE_STUB_DECL(elna_string_type_node) = string_declaration;
+
+        return symbol_table;
+    }
+
+    tree build_composite_type(const std::vector<frontend::type_field>& fields, tree composite_type_node,
+            std::shared_ptr<symbol_table> symbols)
+    {
+        for (auto& field : fields)
+        {
+            tree rewritten_field = get_inner_alias(field.second, symbols);
+            tree field_declaration = build_field(UNKNOWN_LOCATION,
+                    composite_type_node, field.first, rewritten_field);
+            TYPE_FIELDS(composite_type_node) = chainon(TYPE_FIELDS(composite_type_node), field_declaration);
+        }
+        layout_type(composite_type_node);
+        return composite_type_node;
+    }
+
+    tree build_procedure_type(const frontend::procedure_type& procedure, std::shared_ptr<symbol_table> symbols)
+    {
+        std::vector<tree> parameter_types(procedure.parameters.size());
+
+        for (std::size_t i = 0; i < procedure.parameters.size(); ++i)
+        {
+            parameter_types[i] = get_inner_alias(procedure.parameters.at(i), symbols);
+        }
+        tree return_type = void_type_node;
+
+        if (!procedure.return_type.proper_type.empty())
+        {
+            return_type = get_inner_alias(procedure.return_type.proper_type, symbols);
+        }
+        return build_function_type_array(return_type, procedure.parameters.size(), parameter_types.data());
+    }
+
+    tree get_inner_alias(const frontend::type& type, std::shared_ptr<symbol_table> symbols)
+    {
+        if (auto reference = type.get<frontend::primitive_type>())
+        {
+            auto looked_up = symbols->lookup(reference->identifier);
+            gcc_assert(looked_up != NULL_TREE);
+
+            return TREE_TYPE(looked_up);
+        }
+        else if (auto reference = type.get<frontend::record_type>())
+        {
+            tree composite_type_node = make_node(RECORD_TYPE);
+
+            build_composite_type(reference->fields, composite_type_node, symbols);
+
+            return composite_type_node;
+        }
+        else if (auto reference = type.get<frontend::union_type>())
+        {
+            tree composite_type_node = make_node(UNION_TYPE);
+
+            build_composite_type(reference->fields, composite_type_node, symbols);
+
+            return composite_type_node;
+        }
+        else if (auto reference = type.get<frontend::enumeration_type>())
+        {
+            return build_enumeration_type(reference->members);
+        }
+        else if (auto reference = type.get<frontend::pointer_type>())
+        {
+            return build_global_pointer_type(get_inner_alias(reference->base, symbols));
+        }
+        else if (auto reference = type.get<frontend::array_type>())
+        {
+            tree base = get_inner_alias(reference->base, symbols);
+
+            return build_static_array_type(base, reference->size);
+        }
+        else if (auto reference = type.get<frontend::procedure_type>())
+        {
+            auto procedure = build_procedure_type(*reference, symbols);
+
+            return build_global_pointer_type(procedure);
+        }
+        else if (auto reference = type.get<frontend::alias_type>())
+        {
+            return TREE_TYPE(handle_symbol(reference->name, reference, symbols));
+        }
+        return error_mark_node;
+    }
+
+    tree handle_symbol(const std::string& symbol_name, std::shared_ptr<frontend::alias_type> reference,
+            std::shared_ptr<symbol_table> symbols)
+    {
+        tree looked_up = symbols->lookup(symbol_name);
+
+        if (looked_up == NULL_TREE)
+        {
+            tree type_tree = get_inner_alias(reference->reference, symbols);
+            looked_up = build_decl(UNKNOWN_LOCATION, TYPE_DECL,
+                    get_identifier(symbol_name.c_str()), type_tree);
+
+            TREE_PUBLIC(looked_up) = 1;
+            if (is_unique_type(type_tree))
+            {
+                TYPE_NAME(type_tree) = DECL_NAME(looked_up);
+                TYPE_STUB_DECL(type_tree) = looked_up;
+            }
+            else
+            {
+                TYPE_NAME(type_tree) = looked_up;
+            }
+            symbols->enter(symbol_name, looked_up);
+        }
+        return looked_up;
+    }
+
+    void declare_procedure(const std::string& name, const frontend::procedure_info& info,
+            std::shared_ptr<symbol_table> symbols)
+    {
+        tree declaration_type = gcc::build_procedure_type(info.symbol, symbols);
+        tree fndecl = build_fn_decl(name.c_str(), declaration_type);
+        symbols->enter(name, fndecl);
+
+        if (info.symbol.return_type.no_return)
+        {
+            TREE_THIS_VOLATILE(fndecl) = 1;
+        }
+        tree resdecl = build_decl(UNKNOWN_LOCATION, RESULT_DECL, NULL_TREE, TREE_TYPE(declaration_type));
+        DECL_CONTEXT(resdecl) = fndecl;
+        DECL_RESULT(fndecl) = resdecl;
+
+        tree argument_chain = NULL_TREE;
+        function_args_iterator parameter_type;
+        function_args_iter_init(&parameter_type, declaration_type);
+
+        std::vector<std::string>::const_iterator parameter_name = info.names.cbegin();
+
+        for (frontend::type parameter : info.symbol.parameters)
+        {
+            tree declaration_tree = build_decl(UNKNOWN_LOCATION, PARM_DECL,
+                get_identifier(parameter_name->c_str()), function_args_iter_cond(&parameter_type));
+            DECL_CONTEXT(declaration_tree) = fndecl;
+            DECL_ARG_TYPE(declaration_tree) = function_args_iter_cond(&parameter_type);
+
+            argument_chain = chainon(argument_chain, declaration_tree);
+            function_args_iter_next(&parameter_type);
+            ++parameter_name;
+        }
+        DECL_ARGUMENTS(fndecl) = argument_chain;
+        TREE_ADDRESSABLE(fndecl) = 1;
+        DECL_EXTERNAL(fndecl) = info.is_extern();
+        TREE_PUBLIC(fndecl) = info.exported;
+    }
+
+    tree declare_variable(const std::string& name, const frontend::variable_info& info,
+            std::shared_ptr<symbol_table> symbols)
+    {
+        auto variable_type = get_inner_alias(info.symbol, symbols);
+        tree declaration_tree = build_decl(UNKNOWN_LOCATION, VAR_DECL, get_identifier(name.c_str()), variable_type);
+
+        TREE_ADDRESSABLE(declaration_tree) = 1;
+        DECL_EXTERNAL(declaration_tree) = info.is_extern;
+        TREE_PUBLIC(declaration_tree) = info.exported;
+
+        symbols->enter(name, declaration_tree);
+
+        return declaration_tree;
+    }
+
+    void declare_type(const std::string& name, const frontend::type_info& info, std::shared_ptr<symbol_table> symbols)
+    {
+        // The top level symbol table has basic (builtin) types in it which are not aliases.
+        if (auto alias_type = info.symbol.get<frontend::alias_type>())
+        {
+            tree type_declaration = handle_symbol(name, alias_type, symbols);
+
+            TREE_PUBLIC(type_declaration) = info.exported;
+        }
+    }
+
+    void rewrite_symbol_table(std::shared_ptr<frontend::symbol_table> info_table, std::shared_ptr<symbol_table> symbols)
+    {
+        for (auto& [symbol_name, symbol_info] : *info_table)
+        {
+            if (auto type_info = symbol_info->is_type())
+            {
+                declare_type(symbol_name, *type_info, symbols);
+            }
+            else if (auto variable_info = symbol_info->is_variable())
+            {
+                declare_variable(symbol_name, *variable_info, symbols);
+            }
+            else if (auto procedure_info = symbol_info->is_procedure())
+            {
+                declare_procedure(symbol_name, *procedure_info, symbols);
+            }
+        }
+    }
+}

gcc/elna-diagnostic.cc

@@ -0,0 +1,167 @@
+/* Elna frontend specific diagnostic routines.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/gcc/elna-diagnostic.h"
+#include "elna/gcc/elna-tree.h"
+#include "elna/gcc/elna1.h"
+
+namespace elna::gcc
+{
+    linemap_guard::linemap_guard(const char *filename)
+    {
+        linemap_add(line_table, LC_ENTER, 0, filename, 1);
+    }
+
+    linemap_guard::~linemap_guard()
+    {
+        linemap_add(line_table, LC_LEAVE, 0, NULL, 0);
+    }
+
+    location_t get_location(const frontend::position *position)
+    {
+        linemap_line_start(line_table, position->line, 0);
+
+        return linemap_position_for_column(line_table, position->column);
+    }
+
+    std::string print_aggregate_name(tree type, const std::string& kind_name)
+    {
+        if (TYPE_IDENTIFIER(type) == NULL_TREE)
+        {
+            return kind_name;
+        }
+        else
+        {
+            return std::string(IDENTIFIER_POINTER(TYPE_IDENTIFIER(type)));
+        }
+    }
+
+    std::string print_type(tree type)
+    {
+        gcc_assert(TYPE_P(type));
+
+        tree unqualified_type = get_qualified_type(type, TYPE_UNQUALIFIED);
+        tree_code code = TREE_CODE(type);
+
+        if (unqualified_type == elna_int_type_node)
+        {
+            return "Int";
+        }
+        else if (unqualified_type == elna_word_type_node)
+        {
+            return "Word";
+        }
+        else if (unqualified_type == elna_bool_type_node)
+        {
+            return "Bool";
+        }
+        else if (unqualified_type == elna_pointer_type_node)
+        {
+            return "Pointer";
+        }
+        else if (unqualified_type == elna_float_type_node)
+        {
+            return "Float";
+        }
+        else if (unqualified_type == elna_char_type_node)
+        {
+            return "Char";
+        }
+        else if (unqualified_type == elna_string_type_node)
+        {
+            return "String";
+        }
+        else if (is_void_type(unqualified_type)) // For procedures without a return type.
+        {
+            return "()";
+        }
+        else if (POINTER_TYPE_P(unqualified_type))
+        {
+            tree pointer_target_type = TREE_TYPE(type);
+
+            if (TREE_CODE(pointer_target_type) == FUNCTION_TYPE)
+            {
+                return print_type(pointer_target_type);
+            }
+            else
+            {
+                return std::string("^" + print_type(pointer_target_type));
+            }
+        }
+        else if (code == FUNCTION_TYPE)
+        {
+            std::string output = "proc(";
+            tree parameter_type = TYPE_ARG_TYPES(type);
+            while (TREE_VALUE(parameter_type) != void_type_node)
+            {
+                output += print_type(TREE_VALUE(parameter_type));
+                parameter_type = TREE_CHAIN(parameter_type);
+                if (TREE_VALUE(parameter_type) == void_type_node)
+                {
+                    break;
+                }
+                else
+                {
+                    output += ", ";
+                }
+            }
+            output += ')';
+            tree return_type = TREE_TYPE(type);
+
+            if (!is_void_type(return_type))
+            {
+                output += " -> " + print_type(return_type);
+            }
+            return output;
+        }
+        else if (code == ARRAY_TYPE)
+        {
+            return "array";
+        }
+        else if (code == RECORD_TYPE)
+        {
+            return print_aggregate_name(unqualified_type, "record");
+        }
+        else if (code == UNION_TYPE)
+        {
+            return print_aggregate_name(unqualified_type, "union");
+        }
+        else if (code == ENUMERAL_TYPE)
+        {
+            return print_aggregate_name(unqualified_type, "enumeration");
+        }
+        else
+        {
+            return "<<unknown-type>>";
+        }
+        gcc_unreachable();
+    }
+
+    void report_errors(const std::deque<std::unique_ptr<frontend::error>>& errors)
+    {
+        for (const auto& error : errors)
+        {
+            location_t gcc_location{ UNKNOWN_LOCATION };
+
+            if (error->position.line != 0 || error->position.column != 0)
+            {
+                gcc_location = elna::gcc::get_location(&error->position);
+            }
+            error_at(gcc_location, error->what().c_str());
+        }
+    }
+}

gcc/elna-spec.cc

@@ -0,0 +1,31 @@
+/* Specific flags and argument handling of the Elna front end.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+void lang_specific_driver(struct cl_decoded_option ** /* in_decoded_options */,
+        unsigned int * /* in_decoded_options_count */,
+        int * /*in_added_libraries */)
+{
+}
+
+/* Called before linking.  Returns 0 on success and -1 on failure.  */
+int lang_specific_pre_link(void)
+{
+    return 0;
+}
+
+/* Number of extra output files that lang_specific_pre_link may generate.  */
+int lang_specific_extra_outfiles = 0;

gcc/elna-tree.cc

@@ -0,0 +1,315 @@
+/* Utilities to manipulate GCC trees.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "elna/gcc/elna-tree.h"
+#include "elna/gcc/elna-diagnostic.h"
+#include "elna/gcc/elna1.h"
+
+#include "function.h"
+#include "stor-layout.h"
+#include "diagnostic-core.h"
+
+namespace elna::gcc
+{
+    bool is_integral_type(tree type)
+    {
+        gcc_assert(TYPE_P(type));
+        return TREE_CODE(type) == INTEGER_TYPE && type != elna_char_type_node;
+    }
+
+    bool is_numeric_type(tree type)
+    {
+        return is_integral_type(type) || type == elna_float_type_node;
+    }
+
+    bool is_unique_type(tree type)
+    {
+        gcc_assert(TYPE_P(type));
+        return RECORD_OR_UNION_TYPE_P(type) || TREE_CODE(type) == ENUMERAL_TYPE;
+    }
+
+    bool is_void_type(tree type)
+    {
+        return type == NULL_TREE || type == void_type_node;
+    }
+
+    bool is_castable_type(tree type)
+    {
+        gcc_assert(TYPE_P(type));
+        return INTEGRAL_TYPE_P(type) || POINTER_TYPE_P(type) || TREE_CODE(type) == REAL_TYPE;
+    }
+
+    bool are_compatible_pointers(tree lhs_type, tree rhs)
+    {
+        gcc_assert(TYPE_P(lhs_type));
+        tree rhs_type = TREE_TYPE(rhs);
+
+        return (POINTER_TYPE_P(lhs_type) && rhs == elna_pointer_nil_node)
+            || (POINTER_TYPE_P(lhs_type) && lhs_type == rhs_type);
+    }
+
+    tree prepare_rvalue(tree rvalue)
+    {
+        if (DECL_P(rvalue) && TREE_CODE(TREE_TYPE(rvalue)) == FUNCTION_TYPE)
+        {
+            return build1(ADDR_EXPR, build_pointer_type_for_mode(TREE_TYPE(rvalue), VOIDmode, true), rvalue);
+        }
+        else
+        {
+            return rvalue;
+        }
+    }
+
+    bool is_assignable_from(tree assignee, tree assignment)
+    {
+        return get_qualified_type(TREE_TYPE(assignment), TYPE_UNQUALIFIED) == assignee
+            || are_compatible_pointers(assignee, assignment);
+    }
+
+    void append_statement(tree statement_tree)
+    {
+        if (!vec_safe_is_empty(f_binding_level->defers))
+        {
+            append_to_statement_list(statement_tree, &f_binding_level->defers->begin()->try_statements);
+        }
+        else
+        {
+            append_to_statement_list(statement_tree, &f_binding_level->statement_list);
+        }
+    }
+
+    void defer(tree statement_tree)
+    {
+        defer_scope new_defer{ statement_tree, alloc_stmt_list() };
+        vec_safe_insert(f_binding_level->defers, 0, new_defer);
+    }
+
+    tree chain_defer()
+    {
+        if (vec_safe_is_empty(f_binding_level->defers))
+        {
+            return f_binding_level->statement_list;
+        }
+        defer_scope *defer_iterator = f_binding_level->defers->begin();
+        tree defer_tree = build2(TRY_FINALLY_EXPR, void_type_node,
+                defer_iterator->try_statements, defer_iterator->defer_block);
+        int i;
+
+        FOR_EACH_VEC_ELT_FROM(*f_binding_level->defers, i, defer_iterator, 1)
+        {
+            append_to_statement_list(defer_tree, &defer_iterator->try_statements);
+            defer_tree = build2(TRY_FINALLY_EXPR, void_type_node,
+                    defer_iterator->try_statements, defer_iterator->defer_block);
+        }
+        return build2(COMPOUND_EXPR, TREE_TYPE(defer_tree), f_binding_level->statement_list, defer_tree);
+    }
+
+    tree build_field(location_t location, tree record_type, const std::string name, tree type)
+    {
+        tree field_declaration = build_decl(location,
+                FIELD_DECL, get_identifier(name.c_str()), type);
+        TREE_ADDRESSABLE(field_declaration) = 1;
+        DECL_CONTEXT(field_declaration) = record_type;
+
+        return field_declaration;
+    }
+
+    tree do_pointer_arithmetic(frontend::binary_operator binary_operator,
+            tree left, tree right, location_t operation_location)
+    {
+        tree left_type = get_qualified_type(TREE_TYPE(left), TYPE_UNQUALIFIED);
+        tree right_type = get_qualified_type(TREE_TYPE(right), TYPE_UNQUALIFIED);
+        if (binary_operator == frontend::binary_operator::sum)
+        {
+            tree pointer{ NULL_TREE };
+            tree offset{ NULL_TREE };
+            tree pointer_type{ NULL_TREE };
+
+            if (POINTER_TYPE_P(left_type) && is_integral_type(right_type))
+            {
+                pointer = left;
+                offset = right;
+                pointer_type = left_type;
+            }
+            else if (is_integral_type(left_type) && POINTER_TYPE_P(right_type))
+            {
+                pointer = right;
+                offset = left;
+                pointer_type = right_type;
+            }
+            else
+            {
+                return error_mark_node;
+            }
+            tree size_exp = pointer_type == elna_pointer_type_node
+                ? size_one_node
+                : fold_convert(TREE_TYPE(offset), size_in_bytes(TREE_TYPE(TREE_TYPE(pointer))));
+
+            offset = fold_build2(MULT_EXPR, TREE_TYPE(offset), offset, size_exp);
+            offset = fold_convert(sizetype, offset);
+
+            return fold_build2_loc(operation_location, POINTER_PLUS_EXPR, TREE_TYPE(pointer), pointer, offset);
+        }
+        else if (binary_operator == frontend::binary_operator::subtraction)
+        {
+            if (POINTER_TYPE_P(left_type) && is_integral_type(right_type))
+            {
+                tree pointer_type = left_type;
+                tree offset_type = right_type;
+                tree size_exp = fold_convert(offset_type, size_in_bytes(TREE_TYPE(pointer_type)));
+
+                tree convert_expression = fold_build2(MULT_EXPR, offset_type, right, size_exp);
+                convert_expression = fold_convert(sizetype, convert_expression);
+
+                convert_expression = fold_build1(NEGATE_EXPR, sizetype, convert_expression);
+                return fold_build2_loc(operation_location, POINTER_PLUS_EXPR, pointer_type, left, convert_expression);
+            }
+            else if (POINTER_TYPE_P(left_type) && POINTER_TYPE_P(right_type) && left_type == right_type)
+            {
+                return fold_build2_loc(operation_location, POINTER_DIFF_EXPR, ssizetype, left, right);
+            }
+        }
+        gcc_unreachable();
+    }
+
+    tree build_binary_operation(bool condition, frontend::binary_expression *expression,
+            tree_code operator_code, tree left, tree right, tree target_type)
+    {
+        location_t expression_location = get_location(&expression->position());
+        tree left_type = get_qualified_type(TREE_TYPE(left), TYPE_UNQUALIFIED);
+        tree right_type = get_qualified_type(TREE_TYPE(right), TYPE_UNQUALIFIED);
+
+        if (condition)
+        {
+            return fold_build2_loc(expression_location, operator_code, target_type, left, right);
+        }
+        else
+        {
+            error_at(expression_location,
+                    "invalid operands of type '%s' and '%s' for operator %s",
+                    print_type(left_type).c_str(), print_type(right_type).c_str(),
+                    elna::frontend::print_binary_operator(expression->operation()));
+            return error_mark_node;
+        }
+    }
+
+    tree find_field_by_name(location_t expression_location, tree type, const std::string& field_name)
+    {
+        if (type == error_mark_node)
+        {
+            return type;
+        }
+        tree field_declaration = TYPE_FIELDS(type);
+
+        if (!RECORD_OR_UNION_TYPE_P(type))
+        {
+            error_at(expression_location, "Type '%s' does not have a field named '%s'",
+                    print_type(type).c_str(), field_name.c_str());
+            return error_mark_node;
+        }
+        while (field_declaration != NULL_TREE)
+        {
+            tree declaration_name = DECL_NAME(field_declaration);
+            const char *identifier_pointer = IDENTIFIER_POINTER(declaration_name);
+
+            if (field_name == identifier_pointer)
+            {
+                break;
+            }
+            field_declaration = TREE_CHAIN(field_declaration);
+        }
+        if (field_declaration == NULL_TREE)
+        {
+            error_at(expression_location, "Aggregate type does not have a field '%s'", field_name.c_str());
+            return error_mark_node;
+        }
+        return field_declaration;
+    }
+
+    tree build_global_pointer_type(tree type)
+    {
+        return build_pointer_type_for_mode(type, VOIDmode, true);
+    }
+
+    tree build_static_array_type(tree type, const std::uint64_t size)
+    {
+        tree upper_bound = build_int_cst_type(integer_type_node, size);
+        tree range_type = build_range_type(integer_type_node, size_one_node, upper_bound);
+
+        return build_array_type(type, range_type);
+    }
+
+    tree build_enumeration_type(const std::vector<std::string>& members)
+    {
+        tree composite_type_node = make_node(ENUMERAL_TYPE);
+        const tree base_type = integer_type_node;
+
+        TREE_TYPE(composite_type_node) = base_type;
+        ENUM_IS_SCOPED(composite_type_node) = 1;
+
+        tree *pp = &TYPE_VALUES(composite_type_node);
+        std::size_t order{ 1 };
+
+        for (const std::string& member : members)
+        {
+            tree member_name = get_identifier(member.c_str());
+            tree member_declaration = build_decl(UNKNOWN_LOCATION, CONST_DECL, member_name, composite_type_node);
+
+            DECL_CONTEXT(member_declaration) = composite_type_node;
+            DECL_INITIAL(member_declaration) = build_int_cst_type(composite_type_node, order++);
+            TREE_CONSTANT(member_declaration) = 1;
+            TREE_READONLY(member_declaration) = 1;
+
+            TYPE_MAX_VALUE(composite_type_node) = DECL_INITIAL(member_declaration);
+
+            *pp = build_tree_list(member_name, member_declaration);
+            pp = &TREE_CHAIN(*pp);
+        }
+        TYPE_MIN_VALUE(composite_type_node) = DECL_INITIAL(TREE_VALUE(TYPE_VALUES(composite_type_node)));
+        TYPE_UNSIGNED(composite_type_node) = TYPE_UNSIGNED(base_type);
+        SET_TYPE_ALIGN(composite_type_node, TYPE_ALIGN(base_type));
+        TYPE_SIZE(composite_type_node) = NULL_TREE;
+        TYPE_PRECISION(composite_type_node) = TYPE_PRECISION(base_type);
+
+        layout_type(composite_type_node);
+        return composite_type_node;
+    }
+
+    tree build_label_decl(const char *name, location_t loc)
+    {
+        auto label_decl = build_decl(loc, LABEL_DECL, get_identifier(name), void_type_node);
+
+        DECL_CONTEXT(label_decl) = current_function_decl;
+
+        return label_decl;
+    }
+
+    tree extract_constant(tree expression)
+    {
+        int code = TREE_CODE(expression);
+
+        if (code == CONST_DECL)
+        {
+            return DECL_INITIAL(expression);
+        }
+        else if (TREE_CODE_CLASS(code) == tcc_constant)
+        {
+            return expression;
+        }
+        return NULL_TREE;
+    }
+}

gcc/elna1.cc

@@ -0,0 +1,256 @@
+/* Language-dependent hooks for Elna.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "target.h"
+#include "function.h"
+#include "tree.h"
+#include "elna/gcc/elna1.h"
+#include "diagnostic.h"
+#include "opts.h"
+#include "debug.h"
+#include "langhooks.h"
+#include "langhooks-def.h"
+
+#include <fstream>
+#include "elna/frontend/dependency.h"
+#include "elna/gcc/elna-tree.h"
+#include "elna/gcc/elna-generic.h"
+#include "elna/gcc/elna-diagnostic.h"
+#include "elna/gcc/elna-builtins.h"
+
+tree elna_global_trees[ELNA_TI_MAX];
+hash_map<nofree_string_hash, tree> *elna_global_decls = nullptr;
+
+/* The resulting tree type.  */
+
+union GTY ((desc("TREE_CODE (&%h.generic) == IDENTIFIER_NODE"),
+            chain_next("CODE_CONTAINS_STRUCT (TREE_CODE (&%h.generic), "
+                "TS_COMMON) ? ((union lang_tree_node *) TREE_CHAIN "
+                "(&%h.generic)) : NULL"))) lang_tree_node
+{
+    union tree_node GTY ((tag ("0"), desc ("tree_node_structure (&%h)"))) generic;
+};
+
+/* Language hooks.  */
+
+static bool elna_langhook_init(void)
+{
+    build_common_tree_nodes(false);
+
+    elna::gcc::init_ttree();
+    elna_global_decls = hash_map<nofree_string_hash, tree>::create_ggc(default_hash_map_size);
+
+    build_common_builtin_nodes();
+
+    return true;
+}
+
+using dependency_state = elna::frontend::dependency_state<std::shared_ptr<elna::gcc::symbol_table>>;
+
+static elna::frontend::dependency elna_parse_file(dependency_state& state, const char *filename)
+{
+    std::ifstream entry_point{ filename, std::ios::in };
+
+    if (!entry_point)
+    {
+        fatal_error(UNKNOWN_LOCATION, "Cannot open filename %s: %m", filename);
+    }
+    elna::gcc::linemap_guard{ filename };
+    elna::frontend::dependency outcome = elna::frontend::read_source(entry_point, filename);
+
+    if (outcome.has_errors())
+    {
+        elna::gcc::report_errors(outcome.errors());
+        return outcome;
+    }
+    elna::frontend::symbol_bag outcome_bag = elna::frontend::symbol_bag{ std::move(outcome.unresolved), state.globals };
+
+    for (const auto& sub_tree : outcome.tree->imports)
+    {
+        std::filesystem::path sub_path = "source" / elna::frontend::build_path(sub_tree->segments);
+        std::unordered_map<std::filesystem::path, elna::frontend::symbol_bag>::const_iterator cached_import =
+            state.cache.find(sub_path);
+
+        if (cached_import == state.cache.end())
+        {
+            elna_parse_file(state, sub_path.c_str());
+            cached_import = state.cache.find(sub_path);
+        }
+        outcome_bag.add_import(cached_import->second);
+    }
+    outcome.errors() = analyze_semantics(filename, outcome.tree, outcome_bag);
+
+    if (outcome.has_errors())
+    {
+        elna::gcc::report_errors(outcome.errors());
+        return outcome;
+    }
+    state.cache.insert({ filename, outcome_bag });
+    elna::gcc::rewrite_symbol_table(outcome_bag.leave(), state.custom);
+
+    return outcome;
+}
+
+static void elna_langhook_parse_file(void)
+{
+    dependency_state state{ elna::gcc::builtin_symbol_table() };
+
+    for (unsigned int i = 0; i < num_in_fnames; i++)
+    {
+        elna::frontend::dependency outcome = elna_parse_file(state, in_fnames[i]);
+
+        linemap_add(line_table, LC_ENTER, 0, in_fnames[i], 1);
+        elna::gcc::generic_visitor generic_visitor{ state.custom, state.cache.find(in_fnames[i])->second };
+        outcome.tree->accept(&generic_visitor);
+        linemap_add(line_table, LC_LEAVE, 0, NULL, 0);
+    }
+}
+
+static tree elna_langhook_type_for_mode(enum machine_mode mode, int unsignedp)
+{
+    if (mode == TYPE_MODE(float_type_node))
+    {
+        return float_type_node;
+    }
+    else if (mode == TYPE_MODE(double_type_node))
+    {
+        return double_type_node;
+    }
+    if (mode == TYPE_MODE(intQI_type_node))
+    {
+        return unsignedp ? unsigned_intQI_type_node : intQI_type_node;
+    }
+    else if (mode == TYPE_MODE(intHI_type_node))
+    {
+        return unsignedp ? unsigned_intHI_type_node : intHI_type_node;
+    }
+    else if (mode == TYPE_MODE(intSI_type_node))
+    {
+        return unsignedp ? unsigned_intSI_type_node : intSI_type_node;
+    }
+    else if (mode == TYPE_MODE(intDI_type_node))
+    {
+        return unsignedp ? unsigned_intDI_type_node : intDI_type_node;
+    }
+    else if (mode == TYPE_MODE(intTI_type_node))
+    {
+        return unsignedp ? unsigned_intTI_type_node : intTI_type_node;
+    }
+    else if (mode == TYPE_MODE(integer_type_node))
+    {
+        return unsignedp ? unsigned_type_node : integer_type_node;
+    }
+    else if (mode == TYPE_MODE(long_integer_type_node))
+    {
+        return unsignedp ? long_unsigned_type_node : long_integer_type_node;
+    }
+    else if (mode == TYPE_MODE(long_long_integer_type_node))
+    {
+        return unsignedp
+            ? long_long_unsigned_type_node
+            : long_long_integer_type_node;
+    }
+    if (COMPLEX_MODE_P(mode))
+    {
+        if (mode == TYPE_MODE(complex_float_type_node))
+        {
+            return complex_float_type_node;
+        }
+        if (mode == TYPE_MODE(complex_double_type_node))
+        {
+            return complex_double_type_node;
+        }
+        if (mode == TYPE_MODE(complex_long_double_type_node))
+        {
+            return complex_long_double_type_node;
+        }
+        if (mode == TYPE_MODE(complex_integer_type_node) && !unsignedp)
+        {
+            return complex_integer_type_node;
+        }
+    }
+    /* gcc_unreachable */
+    return nullptr;
+}
+
+static bool global_bindings_p(void)
+{
+    return current_function_decl == NULL_TREE;
+}
+
+static tree pushdecl(tree decl)
+{
+    return decl;
+}
+
+static tree elna_langhook_builtin_function(tree decl)
+{
+    elna_global_decls->put(IDENTIFIER_POINTER(DECL_NAME(decl)), decl);
+    return decl;
+}
+
+static unsigned int elna_langhook_option_lang_mask(void)
+{
+    return CL_Elna;
+}
+
+/* Creates an expression whose value is that of EXPR, converted to type TYPE.
+   This function implements all reasonable scalar conversions.  */
+tree convert(tree type, tree expr)
+{
+    if (error_operand_p(type) || error_operand_p(expr))
+    {
+        return error_mark_node;
+    }
+    if (TREE_TYPE(expr) == type)
+    {
+        return expr;
+    }
+    return error_mark_node;
+}
+
+#undef LANG_HOOKS_NAME
+#define LANG_HOOKS_NAME "GNU Elna"
+
+#undef LANG_HOOKS_INIT
+#define LANG_HOOKS_INIT elna_langhook_init
+
+#undef LANG_HOOKS_PARSE_FILE
+#define LANG_HOOKS_PARSE_FILE elna_langhook_parse_file
+
+#undef LANG_HOOKS_TYPE_FOR_MODE
+#define LANG_HOOKS_TYPE_FOR_MODE elna_langhook_type_for_mode
+
+#undef LANG_HOOKS_GETDECLS
+#define LANG_HOOKS_GETDECLS hook_tree_void_null
+
+#undef LANG_HOOKS_BUILTIN_FUNCTION
+#define LANG_HOOKS_BUILTIN_FUNCTION elna_langhook_builtin_function
+
+#undef LANG_HOOKS_IDENTIFIER_SIZE
+#define LANG_HOOKS_IDENTIFIER_SIZE sizeof(struct tree_identifier)
+
+#undef LANG_HOOKS_OPTION_LANG_MASK
+#define LANG_HOOKS_OPTION_LANG_MASK elna_langhook_option_lang_mask
+
+struct lang_hooks lang_hooks = LANG_HOOKS_INITIALIZER;
+
+#include "gt-elna-elna1.h"
+#include "gtype-elna.h"

gcc/gelna.texi

@@ -0,0 +1,135 @@
+\input texinfo @c -*-texinfo-*-
+@setfilename gelna.info
+@settitle The GNU Elna Compiler
+
+@c Create a separate index for command line options
+@defcodeindex op
+@c Merge the standard indexes into a single one.
+@syncodeindex fn cp
+@syncodeindex vr cp
+@syncodeindex ky cp
+@syncodeindex pg cp
+@syncodeindex tp cp
+
+@include gcc-common.texi
+
+@c Copyright years for this manual.
+@set copyrights-elna 2025
+
+@copying
+@c man begin COPYRIGHT
+Copyright @copyright{} @value{copyrights-elna} Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.3 or
+any later version published by the Free Software Foundation; with no
+Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
+A copy of the license is included in the
+@c man end
+section entitled ``GNU Free Documentation License''.
+@ignore
+@c man begin COPYRIGHT
+man page gfdl(7).
+@c man end
+@end ignore
+@end copying
+
+@ifinfo
+@format
+@dircategory Software development
+@direntry
+* Gelna: (gelna).           A GCC-based compiler for the Elna language
+@end direntry
+@end format
+
+@insertcopying
+@end ifinfo
+
+@titlepage
+@title The GNU Elna Compiler
+@versionsubtitle
+@author Eugen Wissner
+
+@page
+@vskip 0pt plus 1filll
+Published by the Free Software Foundation @*
+51 Franklin Street, Fifth Floor@*
+Boston, MA 02110-1301, USA@*
+@sp 1
+@insertcopying
+@end titlepage
+@contents
+@page
+
+@node Top
+@top Introduction
+
+This manual describes how to use @command{gelna}, the GNU compiler for
+the Elna programming language.  This manual is specifically about how to
+invoke @command{gelna}.
+
+@menu
+* Copying::                     The GNU General Public License.
+* GNU Free Documentation License::
+                                How you can share and copy this manual.
+* Invoking gelna::              How to run gelna.
+* Option Index::                Index of command line options.
+* Keyword Index::               Index of concepts.
+@end menu
+
+
+@include gpl_v3.texi
+
+@include fdl.texi
+
+
+@node Invoking gelna
+@chapter Invoking gelna
+
+@c man title gelna A GCC-based compiler for the Elna language
+
+@ignore
+@c man begin SYNOPSIS gelna
+gelna [@option{-c}|@option{-S}]
+      [@option{-g}] [@option{-pg}]
+      [@option{-o} @var{outfile}] @var{infile}@dots{}
+
+Only the most useful options are listed here; see below for the
+remainder.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7), gcc(1)
+and the Info entries for @file{gelna} and @file{gcc}.
+@c man end
+@end ignore
+
+@c man begin DESCRIPTION gelna
+
+The @command{gelna} command is a frontend to @command{gcc} and
+supports many of the same options.  @xref{Option Summary, , Option
+Summary, gcc, Using the GNU Compiler Collection (GCC)}.  This manual
+only documents the options specific to @command{gelna}.
+
+@c man end
+
+@c man begin OPTIONS gelna
+
+@c man end
+
+@node Option Index
+@unnumbered Option Index
+
+@command{gelna}'s command line options are indexed here without any
+initial @samp{-} or @samp{--}.  Where an option has both positive and
+negative forms (such as -foption and -fno-option), relevant entries in
+the manual are indexed under the most appropriate form; it may sometimes
+be useful to look up both forms.
+
+@printindex op
+
+@node Keyword Index
+@unnumbered Keyword Index
+
+@printindex cp
+
+@bye

gcc/lang-specs.h

@@ -0,0 +1,28 @@
+/* GCC driver specs for Elna frontend.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+/* gcc/gcc.cc */
+{".elna",  "@elna", nullptr, 0, 0},
+{"@elna",
+    "elna1 %i \
+    %{!Q:-quiet} " DUMPS_OPTIONS("") " %{m*} %{aux-info*} \
+    %{g*} %{O*} %{W*&pedantic*} %{w} %{std*&ansi&trigraphs} \
+    %{pg:-p} %{p} %{f*} %{undef} \
+    %{!fsyntax-only:%{S:%W{o*}%{!o*:-o %w%b.s}}} \
+    %{fsyntax-only:-o %j} %{-param*} \
+    %{!fsyntax-only:%(invoke_as)}",
+    nullptr, 0, 0},

gcc/lang.opt

@@ -0,0 +1,23 @@
+; lang.opt -- Options for the Elna front end.
+; Copyright (C) 2025 Free Software Foundation, Inc.
+;
+; GCC is free software; you can redistribute it and/or modify it under
+; the terms of the GNU General Public License as published by the Free
+; Software Foundation; either version 3, or (at your option) any later
+; version.
+;
+; GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+; WARRANTY; without even the implied warranty of MERCHANTABILITY or
+; FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+; for more details.
+;
+; You should have received a copy of the GNU General Public License
+; along with GCC; see the file COPYING3.  If not see
+; <http://www.gnu.org/licenses/>.
+
+; See the GCC internals manual for a description of this file's format.
+
+; Please try to keep this file in ASCII collating order.
+
+Language
+Elna

gcc/lang.opt.urls

@@ -0,0 +1,2 @@
+; Autogenerated by regenerate-opt-urls.py from gcc/lang.opt and generated HTML
+

include/elna/frontend/ast.h

@@ -0,0 +1,815 @@
+/* Abstract syntax tree representation.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <vector>
+#include <optional>
+#include "elna/frontend/symbol.h"
+#include "elna/frontend/result.h"
+
+namespace elna::frontend
+{
+    enum class binary_operator
+    {
+        sum,
+        subtraction,
+        multiplication,
+        division,
+        remainder,
+        equals,
+        not_equals,
+        less,
+        greater,
+        less_equal,
+        greater_equal,
+        disjunction,
+        conjunction,
+        exclusive_disjunction,
+        shift_left,
+        shift_right
+    };
+
+    enum class unary_operator
+    {
+        reference,
+        negation,
+        minus
+    };
+
+    class variable_declaration;
+    class constant_declaration;
+    class procedure_declaration;
+    class type_declaration;
+    class procedure_call;
+    class cast_expression;
+    class assign_statement;
+    class if_statement;
+    class import_declaration;
+    class while_statement;
+    class return_statement;
+    class case_statement;
+    class traits_expression;
+    class unit;
+    class program;
+    class binary_expression;
+    class unary_expression;
+    class named_type_expression;
+    class array_type_expression;
+    class pointer_type_expression;
+    class record_type_expression;
+    class union_type_expression;
+    class procedure_type_expression;
+    class enumeration_type_expression;
+    class variable_expression;
+    class array_access_expression;
+    class field_access_expression;
+    class dereference_expression;
+    class designator_expression;
+    class literal_expression;
+    template<typename T>
+    class literal;
+    class defer_statement;
+
+    /**
+     * Interface for AST visitors.
+     */
+    struct parser_visitor
+    {
+        virtual void visit(variable_declaration *) = 0;
+        virtual void visit(constant_declaration *) = 0;
+        virtual void visit(procedure_declaration *) = 0;
+        virtual void visit(type_declaration *) = 0;
+        virtual void visit(procedure_call *) = 0;
+        virtual void visit(cast_expression *) = 0;
+        virtual void visit(traits_expression *) = 0;
+        virtual void visit(assign_statement *) = 0;
+        virtual void visit(if_statement *) = 0;
+        virtual void visit(import_declaration *) = 0;
+        virtual void visit(while_statement *) = 0;
+        virtual void visit(return_statement *) = 0;
+        virtual void visit(defer_statement *) = 0;
+        virtual void visit(case_statement *) = 0;
+        virtual void visit(unit *) = 0;
+        virtual void visit(program *) = 0;
+        virtual void visit(binary_expression *) = 0;
+        virtual void visit(unary_expression *) = 0;
+        virtual void visit(named_type_expression *) = 0;
+        virtual void visit(array_type_expression *) = 0;
+        virtual void visit(pointer_type_expression *) = 0;
+        virtual void visit(record_type_expression *) = 0;
+        virtual void visit(union_type_expression *) = 0;
+        virtual void visit(procedure_type_expression *) = 0;
+        virtual void visit(enumeration_type_expression *) = 0;
+        virtual void visit(variable_expression *) = 0;
+        virtual void visit(array_access_expression *) = 0;
+        virtual void visit(field_access_expression *) = 0;
+        virtual void visit(dereference_expression *) = 0;
+        virtual void visit(literal<std::int32_t> *) = 0;
+        virtual void visit(literal<std::uint32_t> *) = 0;
+        virtual void visit(literal<double> *) = 0;
+        virtual void visit(literal<bool> *) = 0;
+        virtual void visit(literal<unsigned char> *) = 0;
+        virtual void visit(literal<std::nullptr_t> *) = 0;
+        virtual void visit(literal<std::string> *) = 0;
+    };
+
+    /**
+     * Abstract visitor that doesn't visit any nodes by default.
+     */
+    class empty_visitor : public parser_visitor
+    {
+        [[noreturn]] void not_implemented();
+
+    public:
+        [[noreturn]] virtual void visit(named_type_expression *) override;
+        [[noreturn]] virtual void visit(array_type_expression *) override;
+        [[noreturn]] virtual void visit(pointer_type_expression *) override;
+        [[noreturn]] virtual void visit(program *) override;
+        [[noreturn]] virtual void visit(type_declaration *) override;
+        [[noreturn]] virtual void visit(record_type_expression *) override;
+        [[noreturn]] virtual void visit(union_type_expression *) override;
+        [[noreturn]] virtual void visit(procedure_type_expression *) override;
+        [[noreturn]] virtual void visit(enumeration_type_expression *) override;
+
+        [[noreturn]] virtual void visit(variable_declaration *) override;
+        [[noreturn]] virtual void visit(constant_declaration *) override;
+        [[noreturn]] virtual void visit(procedure_declaration *) override;
+        [[noreturn]] virtual void visit(assign_statement *) override;
+        [[noreturn]] virtual void visit(if_statement *) override;
+        [[noreturn]] virtual void visit(import_declaration *) override;
+        [[noreturn]] virtual void visit(while_statement *) override;
+        [[noreturn]] virtual void visit(return_statement *) override;
+        [[noreturn]] virtual void visit(defer_statement *) override;
+        [[noreturn]] virtual void visit(case_statement *) override;
+        [[noreturn]] virtual void visit(procedure_call *) override;
+        [[noreturn]] virtual void visit(unit *) override;
+        [[noreturn]] virtual void visit(cast_expression *) override;
+        [[noreturn]] virtual void visit(traits_expression *) override;
+        [[noreturn]] virtual void visit(binary_expression *) override;
+        [[noreturn]] virtual void visit(unary_expression *) override;
+        [[noreturn]] virtual void visit(variable_expression *) override;
+        [[noreturn]] virtual void visit(array_access_expression *) override;
+        [[noreturn]] virtual void visit(field_access_expression *) override;
+        [[noreturn]] virtual void visit(dereference_expression *) override;
+        [[noreturn]] virtual void visit(literal<std::int32_t> *) override;
+        [[noreturn]] virtual void visit(literal<std::uint32_t> *) override;
+        [[noreturn]] virtual void visit(literal<double> *) override;
+        [[noreturn]] virtual void visit(literal<bool> *) override;
+        [[noreturn]] virtual void visit(literal<unsigned char> *) override;
+        [[noreturn]] virtual void visit(literal<std::nullptr_t> *) override;
+        [[noreturn]] virtual void visit(literal<std::string> *) override;
+    };
+
+    /**
+     * AST node.
+     */
+    class node
+    {
+        const struct position source_position;
+
+    protected:
+        /**
+         * \param position Source code position.
+         */
+        explicit node(const position position);
+
+    public:
+        virtual void accept(parser_visitor *visitor) = 0;
+        virtual ~node() = 0;
+
+        /**
+         * \return Node position in the source code.
+         */
+        const struct position& position() const;
+    };
+
+    class statement : public virtual node
+    {
+    };
+
+    class expression : public virtual node
+    {
+    public:
+        virtual cast_expression *is_cast();
+        virtual traits_expression *is_traits();
+        virtual binary_expression *is_binary();
+        virtual unary_expression *is_unary();
+        virtual designator_expression *is_designator();
+        virtual procedure_call *is_call_expression();
+        virtual literal_expression *is_literal();
+    };
+
+    /**
+     * Symbol definition.
+     */
+    class declaration : public node
+    {
+    protected:
+        declaration(const struct position position, identifier_definition identifier);
+
+    public:
+        const identifier_definition identifier;
+    };
+
+    /**
+     * Some type expression.
+     */
+    class type_expression : public node
+    {
+    public:
+        virtual named_type_expression *is_named();
+        virtual array_type_expression *is_array();
+        virtual pointer_type_expression *is_pointer();
+        virtual record_type_expression *is_record();
+        virtual union_type_expression *is_union();
+        virtual procedure_type_expression *is_procedure();
+        virtual enumeration_type_expression *is_enumeration();
+
+    protected:
+        type_expression(const struct position position);
+    };
+
+    /**
+     * Expression refering to a type by its name.
+     */
+    class named_type_expression : public type_expression
+    {
+    public:
+        const std::string name;
+
+        named_type_expression(const struct position position, const std::string& name);
+        void accept(parser_visitor *visitor) override;
+        named_type_expression *is_named() override;
+    };
+
+    class array_type_expression : public type_expression
+    {
+        type_expression *m_base;
+
+    public:
+        const std::uint32_t size;
+
+        array_type_expression(const struct position position,
+                type_expression *base, const std::uint32_t size);
+        ~array_type_expression();
+
+        void accept(parser_visitor *visitor) override;
+        array_type_expression *is_array() override;
+
+        type_expression& base();
+    };
+
+    class pointer_type_expression : public type_expression
+    {
+        type_expression *m_base;
+
+    public:
+        pointer_type_expression(const struct position position, type_expression *base);
+        ~pointer_type_expression();
+
+        void accept(parser_visitor *visitor) override;
+        pointer_type_expression *is_pointer() override;
+
+        type_expression& base();
+    };
+
+    using field_declaration = std::pair<std::string, type_expression *>;
+
+    class record_type_expression : public type_expression
+    {
+    public:
+        const std::vector<field_declaration> fields;
+
+        record_type_expression(const struct position position, std::vector<field_declaration>&& fields);
+        ~record_type_expression();
+
+        void accept(parser_visitor *visitor) override;
+        record_type_expression *is_record() override;
+    };
+
+    class union_type_expression : public type_expression
+    {
+    public:
+        std::vector<field_declaration> fields;
+
+        union_type_expression(const struct position position, std::vector<field_declaration>&& fields);
+        ~union_type_expression();
+
+        void accept(parser_visitor *visitor) override;
+        union_type_expression *is_union() override;
+    };
+
+    /**
+     * Enumeration type.
+     */
+    class enumeration_type_expression : public type_expression
+    {
+    public:
+        const std::vector<std::string> members;
+
+        enumeration_type_expression(const struct position, std::vector<std::string>&& members);
+
+        void accept(parser_visitor *visitor) override;
+        enumeration_type_expression *is_enumeration() override;
+    };
+
+    /**
+     * Variable declaration.
+     */
+    class variable_declaration : public node
+    {
+        std::shared_ptr<type_expression> m_variable_type;
+
+    public:
+        variable_declaration(const struct position position,
+                std::vector<identifier_definition>&& identifier, std::shared_ptr<type_expression> variable_type,
+                expression *body = nullptr);
+        variable_declaration(const struct position position,
+                std::vector<identifier_definition>&& identifier, std::shared_ptr<type_expression> variable_type,
+                std::monostate);
+
+        void accept(parser_visitor *visitor) override;
+
+        bool has_initializer() const;
+
+        const std::vector<identifier_definition> identifiers;
+        type_expression& variable_type();
+        expression *const body{ nullptr };
+        const bool is_extern{ false };
+    };
+
+    /**
+     * Literal expression.
+     */
+    class literal_expression : public expression
+    {
+    public:
+        literal_expression *is_literal() override;
+
+    protected:
+        literal_expression();
+    };
+
+    /**
+     * Constant definition.
+     */
+    class constant_declaration : public declaration
+    {
+        expression *m_body;
+
+    public:
+        constant_declaration(const struct position position, identifier_definition identifier,
+                expression *body);
+        void accept(parser_visitor *visitor) override;
+
+        expression& body();
+
+        virtual ~constant_declaration() override;
+    };
+
+    /**
+     * Procedure type.
+     */
+    class procedure_type_expression : public type_expression
+    {
+    public:
+        using return_t = return_declaration<type_expression *>;
+
+        const return_t return_type;
+        std::vector<type_expression *> parameters;
+
+        procedure_type_expression(const struct position position, return_t return_type = return_t());
+        ~procedure_type_expression();
+
+        void accept(parser_visitor *visitor) override;
+        procedure_type_expression *is_procedure() override;
+    };
+
+    struct block
+    {
+        block(std::vector<constant_declaration*>&& constants, std::vector<variable_declaration *>&& variables,
+                std::vector<statement *>&& body);
+        block(const block&) = delete;
+        block(block&& that);
+
+        block& operator=(const block&) = delete;
+        block& operator=(block&& that);
+
+        const std::vector<variable_declaration *>& variables();
+        const std::vector<constant_declaration *>& constants();
+        const std::vector<statement *>& body();
+
+        virtual ~block();
+
+    private:
+        std::vector<variable_declaration *> m_variables;
+        std::vector<constant_declaration *> m_constants;
+        std::vector<statement *> m_body;
+
+    };
+
+    /**
+     * Procedure definition.
+     */
+    class procedure_declaration : public declaration
+    {
+        procedure_type_expression *m_heading;
+
+    public:
+        std::optional<block> body;
+        std::vector<std::string> parameter_names;
+
+        procedure_declaration(const struct position position, identifier_definition identifier,
+                procedure_type_expression *heading, block&& body);
+        procedure_declaration(const struct position position, identifier_definition identifier,
+                procedure_type_expression *heading);
+        void accept(parser_visitor *visitor) override;
+
+        procedure_type_expression& heading();
+
+        virtual ~procedure_declaration() override;
+    };
+
+    /**
+     * Type definition.
+     */
+    class type_declaration : public declaration
+    {
+        type_expression *m_body;
+
+    public:
+        type_declaration(const struct position position, identifier_definition identifier,
+                type_expression *expression);
+        ~type_declaration();
+
+        void accept(parser_visitor *visitor) override;
+
+        type_expression& body();
+    };
+
+    /**
+     * Cast expression.
+     */
+    class cast_expression : public expression
+    {
+        type_expression *m_target;
+        expression *m_value;
+
+    public:
+        type expression_type;
+
+        cast_expression(const struct position position, type_expression *target, expression *value);
+        void accept(parser_visitor *visitor) override;
+        cast_expression *is_cast() override;
+
+        type_expression& target();
+        expression& value();
+
+        virtual ~cast_expression() override;
+    };
+
+    class traits_expression : public expression
+    {
+    public:
+        std::vector<type_expression *> parameters;
+        const std::string name;
+        std::vector<type> types;
+
+        traits_expression(const struct position position, const std::string& name);
+        ~traits_expression();
+
+        void accept(parser_visitor *visitor) override;
+        traits_expression *is_traits() override;
+    };
+
+    /**
+     * List of statements paired with a condition.
+     */
+    class conditional_statements
+    {
+        expression *m_prerequisite;
+
+    public:
+        const std::vector<statement *> statements;
+
+        conditional_statements(expression *prerequisite, std::vector<statement *>&& statements);
+
+        expression& prerequisite();
+
+        virtual ~conditional_statements();
+    };
+
+    class return_statement : public statement
+    {
+    public:
+        expression *m_return_expression;
+
+        return_statement(const struct position position, expression *return_expression);
+        void accept(parser_visitor *visitor) override;
+
+        expression& return_expression();
+
+        virtual ~return_statement() override;
+    };
+
+    struct switch_case
+    {
+        std::vector<expression *> labels;
+        std::vector<statement *> statements;
+    };
+
+    class case_statement : public statement
+    {
+        expression *m_condition;
+
+    public:
+        const std::vector<switch_case> cases;
+        const std::vector<statement *> *alternative;
+
+        case_statement(const struct position position, expression *condition,
+                std::vector<switch_case>&& cases, std::vector<statement *> *alternative = nullptr);
+        void accept(parser_visitor *visitor) override;
+        expression& condition();
+    };
+
+    class designator_expression : public expression
+    {
+    public:
+        virtual variable_expression *is_variable();
+        virtual array_access_expression *is_array_access();
+        virtual field_access_expression *is_field_access();
+        virtual dereference_expression *is_dereference();
+
+        designator_expression *is_designator() override;
+        void accept(parser_visitor *visitor);
+        ~designator_expression() = 0;
+
+    protected:
+        designator_expression();
+    };
+
+    class variable_expression : public designator_expression, public literal_expression
+    {
+    public:
+        const std::string name;
+
+        variable_expression(const struct position position, const std::string& name);
+        void accept(parser_visitor *visitor) override;
+
+        variable_expression *is_variable() override;
+    };
+
+    class array_access_expression : public designator_expression
+    {
+        expression *m_base;
+        expression *m_index;
+
+    public:
+        array_access_expression(const struct position position, expression *base, expression *index);
+        void accept(parser_visitor *visitor) override;
+
+        expression& base();
+        expression& index();
+
+        array_access_expression *is_array_access() override;
+
+        ~array_access_expression() override;
+    };
+
+    class field_access_expression : public designator_expression
+    {
+        expression *m_base;
+        std::string m_field;
+
+    public:
+        field_access_expression(const struct position position, expression *base,
+                const std::string& field);
+        void accept(parser_visitor *visitor) override;
+
+        expression& base();
+        std::string& field();
+
+        field_access_expression *is_field_access() override;
+
+        ~field_access_expression() override;
+    };
+
+    class dereference_expression : public designator_expression
+    {
+        expression *m_base;
+
+    public:
+        dereference_expression(const struct position position, expression *base);
+        void accept(parser_visitor *visitor) override;
+
+        expression& base();
+
+        dereference_expression *is_dereference() override;
+
+        ~dereference_expression() override;
+    };
+
+    /**
+     * Procedure call expression.
+     */
+    class procedure_call : public expression, public statement
+    {
+        designator_expression *m_callable;
+
+    public:
+        std::vector<expression *> arguments;
+
+        procedure_call(const struct position position, designator_expression *callable);
+        void accept(parser_visitor *visitor) override;
+        virtual procedure_call *is_call_expression() override;
+
+        designator_expression& callable();
+
+        virtual ~procedure_call() override;
+    };
+
+    class assign_statement : public statement
+    {
+        designator_expression *m_lvalue;
+        expression *m_rvalue;
+
+    public:
+        /**
+         * \param position Source code position.
+         * \param lvalue Left-hand side.
+         * \param rvalue Assigned expression.
+         */
+        assign_statement(const struct position position, designator_expression *lvalue,
+                expression *rvalue);
+        void accept(parser_visitor *visitor) override;
+
+        designator_expression& lvalue();
+        expression& rvalue();
+
+        virtual ~assign_statement() override;
+    };
+
+    /**
+     * If-statement.
+     */
+    class if_statement : public statement
+    {
+        conditional_statements *m_body;
+
+    public:
+        const std::vector<conditional_statements *> branches;
+        const std::vector<statement *> *alternative;
+
+        if_statement(const struct position position, conditional_statements *body,
+                std::vector<conditional_statements *>&& branches,
+                std::vector<statement *> *alternative = nullptr);
+        void accept(parser_visitor *visitor) override;
+
+        conditional_statements& body();
+
+        virtual ~if_statement() override;
+    };
+
+    /**
+     * Import statement.
+     */
+    class import_declaration : public node
+    {
+    public:
+        const std::vector<std::string> segments;
+
+        import_declaration(const struct position position, std::vector<std::string>&& segments);
+        void accept(parser_visitor *visitor) override;
+    };
+
+    /**
+     * While-statement.
+     */
+    class while_statement : public statement
+    {
+        conditional_statements *m_body;
+
+    public:
+        const std::vector<conditional_statements *> branches;
+
+        while_statement(const struct position position, conditional_statements *body,
+                std::vector<conditional_statements *>&& branches);
+        void accept(parser_visitor *visitor) override;
+
+        conditional_statements& body();
+
+        virtual ~while_statement() override;
+    };
+
+    class unit : public node
+    {
+    public:
+        std::vector<import_declaration *> imports;
+        std::vector<constant_declaration *> constants;
+        std::vector<type_declaration *> types;
+        std::vector<variable_declaration *> variables;
+        std::vector<procedure_declaration *> procedures;
+
+        unit(const struct position position);
+        virtual void accept(parser_visitor *visitor) override;
+
+        virtual ~unit() override;
+    };
+
+    class program : public unit
+    {
+    public:
+        std::vector<statement *> body;
+
+        program(const struct position position);
+        void accept(parser_visitor *visitor) override;
+
+        virtual ~program() override;
+    };
+
+    template<typename T>
+    class literal : public literal_expression
+    {
+    public:
+        T value;
+
+        literal(const struct position position, const T& value)
+            : node(position), value(value)
+        {
+        }
+
+        void accept(parser_visitor *visitor) override
+        {
+            visitor->visit(this);
+        }
+    };
+
+    class defer_statement : public statement
+    {
+    public:
+        const std::vector<statement *> statements;
+
+        defer_statement(const struct position position, std::vector<statement *>&& statements);
+        void accept(parser_visitor *visitor) override;
+
+        virtual ~defer_statement() override;
+    };
+
+    class binary_expression : public expression
+    {
+        expression *m_lhs;
+        expression *m_rhs;
+        binary_operator m_operator;
+
+    public:
+        binary_expression(const struct position position, expression *lhs,
+                expression *rhs, const binary_operator operation);
+
+        void accept(parser_visitor *visitor) override;
+        binary_expression *is_binary() override;
+
+        expression& lhs();
+        expression& rhs();
+        binary_operator operation() const;
+
+        virtual ~binary_expression() override;
+    };
+
+    class unary_expression : public expression
+    {
+        expression *m_operand;
+        unary_operator m_operator;
+
+    public:
+        unary_expression(const struct position position, expression *operand,
+                const unary_operator operation);
+
+        void accept(parser_visitor *visitor) override;
+        unary_expression *is_unary() override;
+
+        expression& operand();
+        unary_operator operation() const;
+
+        virtual ~unary_expression() override;
+    };
+
+    const char *print_binary_operator(const binary_operator operation);
+}

include/elna/frontend/dependency.h

@@ -0,0 +1,55 @@
+/* Dependency graph analysis.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <filesystem>
+#include <fstream>
+#include "elna/frontend/result.h"
+#include "elna/frontend/ast.h"
+#include "elna/frontend/symbol.h"
+
+namespace elna::frontend
+{
+    class dependency : public error_container
+    {
+        error_list m_errors;
+
+    public:
+        std::unique_ptr<unit> tree;
+        forward_table unresolved;
+
+        explicit dependency(const char *path);
+    };
+
+    dependency read_source(std::istream& entry_point, const char *entry_path);
+    std::filesystem::path build_path(const std::vector<std::string>& segments);
+    error_list analyze_semantics(const char *path, std::unique_ptr<unit>& tree, symbol_bag bag);
+
+    template<typename T>
+    struct dependency_state
+    {
+        const std::shared_ptr<symbol_table> globals;
+        T custom;
+        std::unordered_map<std::filesystem::path, symbol_bag> cache;
+
+        explicit dependency_state(T custom)
+            : globals(builtin_symbol_table()), custom(custom)
+        {
+        }
+    };
+}

include/elna/frontend/driver.h

@@ -0,0 +1,51 @@
+/* Parsing driver.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <optional>
+#include "elna/frontend/ast.h"
+#include "location.hh"
+
+namespace elna::frontend
+{
+    position make_position(const yy::location& location);
+
+    class syntax_error final : public error
+    {
+        std::string message;
+
+    public:
+        syntax_error(const std::string& message,
+                const char *input_file, const yy::location& location);
+
+        virtual std::string what() const override;
+    };
+
+    class driver : public error_container
+    {
+    public:
+        std::unique_ptr<unit> tree;
+
+        driver(const char *input_file);
+    };
+
+    constexpr char escape_invalid_char = '\xff';
+
+    char escape_char(char escape);
+    std::optional<std::string> escape_string(const char *escape);
+}

include/elna/frontend/result.h

@@ -0,0 +1,124 @@
+/* Miscellaneous types used across stage boundaries.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <cstddef>
+#include <string>
+#include <deque>
+#include <memory>
+#include <variant>
+
+namespace elna::frontend
+{
+    /**
+     * Position in the source text.
+     */
+    struct position
+    {
+        /// Line.
+        std::size_t line = 1;
+
+        /// Column.
+        std::size_t column = 1;
+    };
+
+    /**
+     * A compilation error consists of an error message and position.
+     */
+    class error
+    {
+    protected:
+        error(const char *path, const struct position position);
+
+    public:
+        const struct position position;
+        const char *path;
+
+        virtual ~error() = default;
+
+        /// Error text.
+        virtual std::string what() const = 0;
+
+        /// Error line in the source text.
+        std::size_t line() const;
+
+        /// Error column in the source text.
+        std::size_t column() const;
+    };
+
+    using error_list = typename std::deque<std::unique_ptr<error>>;
+
+    class error_container
+    {
+    protected:
+        error_list m_errors;
+
+        error_container(const char *input_file);
+
+    public:
+        const char *input_file;
+
+        error_list& errors();
+
+        template<typename T, typename... Args>
+        void add_error(Args... arguments)
+        {
+            auto new_error = std::make_unique<T>(arguments...);
+            m_errors.emplace_back(std::move(new_error));
+        }
+
+        bool has_errors() const;
+    };
+
+    /**
+     * Tags a procedure type as never returning.
+     */
+    template<typename T>
+    struct return_declaration
+    {
+        return_declaration() = default;
+
+        explicit return_declaration(T type)
+            : proper_type(type)
+        {
+        }
+
+        explicit return_declaration(std::monostate)
+            : no_return(true)
+        {
+        }
+
+        T proper_type{};
+        bool no_return{ false };
+    };
+
+    struct identifier_definition
+    {
+        std::string name;
+        bool exported;
+
+        bool operator==(const identifier_definition& that) const;
+        bool operator==(const std::string& that) const;
+    };
+}
+
+template<>
+struct std::hash<elna::frontend::identifier_definition>
+{
+    std::size_t operator()(const elna::frontend::identifier_definition& key) const noexcept;
+};

include/elna/frontend/semantic.h

@@ -0,0 +1,190 @@
+/* Name analysis.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <string>
+#include <unordered_map>
+#include <memory>
+#include <deque>
+
+#include "elna/frontend/ast.h"
+#include "elna/frontend/result.h"
+#include "elna/frontend/symbol.h"
+
+namespace elna::frontend
+{
+    class undeclared_error : public error
+    {
+        const std::string identifier;
+
+    public:
+        undeclared_error(const std::string& identifier, const char *path, const struct position position);
+
+        std::string what() const override;
+    };
+
+    class already_declared_error : public error
+    {
+        const std::string identifier;
+
+    public:
+        already_declared_error(const std::string& identifier, const char *path, const struct position position);
+
+        std::string what() const override;
+    };
+
+    class field_duplication_error : public error
+    {
+        const std::string field_name;
+
+    public:
+        field_duplication_error(const std::string& field_name, const char *path, const struct position position);
+
+        std::string what() const override;
+    };
+
+    class cyclic_declaration_error : public error
+    {
+        const std::vector<std::string> cycle;
+
+    public:
+        cyclic_declaration_error(const std::vector<std::string>& cycle,
+                const char *path, const struct position position);
+
+        std::string what() const override;
+    };
+
+    class return_error : public error
+    {
+        const std::string identifier;
+
+    public:
+        return_error(const std::string& identifier, const char *path, const struct position position);
+
+        std::string what() const override;
+    };
+
+    class variable_initializer_error : public error
+    {
+    public:
+        variable_initializer_error(const char *path, const struct position position);
+
+        std::string what() const override;
+    };
+
+    /**
+     * Checks types.
+     */
+    class type_analysis_visitor final : public empty_visitor, public error_container
+    {
+        bool returns;
+        symbol_bag bag;
+
+        bool check_unresolved_symbol(std::shared_ptr<alias_type> alias,
+                std::vector<std::string>& path);
+
+    public:
+        explicit type_analysis_visitor(const char *path, symbol_bag bag);
+
+        void visit(program *program) override;
+
+        void visit(procedure_declaration *definition) override;
+        void visit(assign_statement *) override;
+        void visit(if_statement *) override;
+        void visit(while_statement *) override;
+        void visit(return_statement *) override;
+        void visit(defer_statement *) override;
+        void visit(case_statement *) override;
+        void visit(procedure_call *) override;
+        void visit(unit *unit) override;
+        void visit(type_declaration *definition) override;
+    };
+
+    /**
+     * Performs name analysis.
+     */
+    class name_analysis_visitor final : public parser_visitor, public error_container
+    {
+        type current_type;
+        constant_info::variant current_literal;
+
+        symbol_bag bag;
+
+        procedure_type build_procedure(procedure_type_expression& type_expression);
+        std::vector<type_field> build_composite_type(const std::vector<field_declaration>& fields);
+
+    public:
+        name_analysis_visitor(const char *path, symbol_bag bag);
+
+        void visit(named_type_expression *type_expression) override;
+        void visit(array_type_expression *type_expression) override;
+        void visit(pointer_type_expression *type_expression) override;
+        void visit(program *program) override;
+        void visit(type_declaration *definition) override;
+        void visit(record_type_expression *type_expression) override;
+        void visit(union_type_expression *type_expression) override;
+        void visit(procedure_type_expression *type_expression) override;
+        void visit(enumeration_type_expression *type_expression) override;
+
+        void visit(variable_declaration *declaration) override;
+        void visit(constant_declaration *definition) override;
+        void visit(procedure_declaration *definition) override;
+        void visit(assign_statement *statement) override;
+        void visit(if_statement *statement) override;
+        void visit(import_declaration *) override;
+        void visit(while_statement *statement) override;
+        void visit(return_statement *statement) override;
+        void visit(defer_statement *statement) override;
+        void visit(case_statement *statement) override;
+        void visit(procedure_call *call) override;
+        void visit(unit *unit) override;
+        void visit(cast_expression *expression) override;
+        void visit(traits_expression *trait) override;
+        void visit(binary_expression *expression) override;
+        void visit(unary_expression *expression) override;
+        void visit(variable_expression *) override;
+        void visit(array_access_expression *expression) override;
+        void visit(field_access_expression *expression) override;
+        void visit(dereference_expression *expression) override;
+        void visit(literal<std::int32_t> *literal) override;
+        void visit(literal<std::uint32_t> *literal) override;
+        void visit(literal<double> *literal) override;
+        void visit(literal<bool> *literal) override;
+        void visit(literal<unsigned char> *literal) override;
+        void visit(literal<std::nullptr_t> *literal) override;
+        void visit(literal<std::string> *literal) override;
+    };
+
+    /**
+     * Collects global declarations without resolving any symbols.
+     */
+    class declaration_visitor final : public empty_visitor, public error_container
+    {
+    public:
+        forward_table unresolved;
+
+        explicit declaration_visitor(const char *path);
+
+        void visit(program *program) override;
+        void visit(import_declaration *) override;
+        void visit(unit *unit) override;
+        void visit(type_declaration *definition) override;
+        void visit(variable_declaration *declaration) override;
+        void visit(procedure_declaration *definition) override;
+    };
+}

include/elna/frontend/symbol.h

@@ -0,0 +1,457 @@
+/* Symbol definitions.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <cstdint>
+#include <unordered_map>
+#include <string>
+#include <memory>
+#include <vector>
+#include <forward_list>
+
+#include "elna/frontend/result.h"
+
+namespace elna::frontend
+{
+    class alias_type;
+    class primitive_type;
+    class record_type;
+    class union_type;
+    class pointer_type;
+    class array_type;
+    class procedure_type;
+    class enumeration_type;
+
+    class type
+    {
+        enum class type_tag
+        {
+            empty,
+            alias,
+            primitive,
+            record,
+            _union,
+            pointer,
+            array,
+            procedure,
+            enumeration
+        };
+        type_tag tag{ type_tag::empty };
+        union
+        {
+            std::weak_ptr<alias_type> alias;
+            std::shared_ptr<primitive_type> primitive;
+            std::shared_ptr<record_type> record;
+            std::shared_ptr<union_type> _union;
+            std::shared_ptr<pointer_type> pointer;
+            std::shared_ptr<array_type> array;
+            std::shared_ptr<procedure_type> procedure;
+            std::shared_ptr<enumeration_type> enumeration;
+        };
+
+        void copy(const type& other);
+        void move(type&& other);
+
+    public:
+        type();
+        explicit type(std::shared_ptr<alias_type> alias);
+        explicit type(std::shared_ptr<primitive_type> primitive);
+        explicit type(std::shared_ptr<record_type> record);
+        explicit type(std::shared_ptr<union_type> _union);
+        explicit type(std::shared_ptr<pointer_type> pointer);
+        explicit type(std::shared_ptr<array_type> array);
+        explicit type(std::shared_ptr<procedure_type> procedure);
+        explicit type(std::shared_ptr<enumeration_type> enumeration);
+
+        type(const type& other);
+        type& operator=(const type& other);
+
+        type(type&& other);
+        type& operator=(type&& other);
+
+        bool operator==(const std::nullptr_t&);
+
+        ~type();
+
+        template<typename T>
+        std::shared_ptr<T> get() const;
+
+        bool empty() const;
+    };
+
+    struct alias_type
+    {
+        const std::string name;
+        type reference;
+
+        explicit alias_type(const std::string& name);
+    };
+
+    struct pointer_type
+    {
+        const type base;
+
+        explicit pointer_type(type base);
+    };
+
+    struct array_type
+    {
+        const type base;
+        const std::uint64_t size;
+
+        array_type(type base, std::uint64_t size);
+    };
+
+    struct primitive_type
+    {
+        const std::string identifier;
+
+        explicit primitive_type(const std::string& identifier);
+    };
+
+    using type_field = std::pair<std::string, type>;
+
+    struct record_type
+    {
+        std::vector<type_field> fields;
+    };
+
+    struct union_type
+    {
+        std::vector<type_field> fields;
+    };
+
+    struct procedure_type
+    {
+        using return_t = return_declaration<type>;
+
+        std::vector<type> parameters;
+        const return_t return_type;
+
+        procedure_type(return_t return_type = return_t());
+    };
+
+    struct enumeration_type
+    {
+        std::vector<std::string> members;
+
+        explicit enumeration_type(const std::vector<std::string>& members);
+    };
+
+    class type_info;
+    class procedure_info;
+    class constant_info;
+    class variable_info;
+
+    class info : public std::enable_shared_from_this<info>
+    {
+    public:
+        bool exported{ false };
+
+        virtual ~info() = 0;
+
+        virtual std::shared_ptr<type_info> is_type();
+        virtual std::shared_ptr<procedure_info> is_procedure();
+        virtual std::shared_ptr<constant_info> is_constant();
+        virtual std::shared_ptr<variable_info> is_variable();
+    };
+
+    /**
+     * Symbol table.
+     */
+    template<typename T, typename U, U nothing>
+    class symbol_map
+    {
+    public:
+        using symbol_ptr = typename std::enable_if<
+            std::is_convertible<U, T>::value || std::is_assignable<T, U>::value,
+            T
+        >::type;
+        using iterator = typename std::unordered_map<std::string, symbol_ptr>::iterator;
+        using const_iterator = typename std::unordered_map<std::string, symbol_ptr>::const_iterator;
+
+    private:
+        std::unordered_map<std::string, symbol_ptr> entries;
+        std::shared_ptr<symbol_map> outer_scope;
+
+    public:
+        /**
+         * Constructs a new symbol with an optional outer scope.
+         *
+         * \param scope Outer scope.
+         */
+        explicit symbol_map(std::shared_ptr<symbol_map> scope = nullptr)
+            : outer_scope(scope)
+        {
+        }
+
+        iterator begin()
+        {
+            return this->entries.begin();
+        }
+
+        iterator end()
+        {
+            return this->entries.end();
+        }
+
+        const_iterator cbegin() const
+        {
+            return this->entries.cbegin();
+        }
+
+        const_iterator cend() const
+        {
+            return this->entries.cend();
+        }
+
+        /**
+         * \return Symbol count in the current scope.
+         */
+        std::size_t size() const
+        {
+            return this->entries.size();
+        }
+
+        /**
+         * Looks for symbol in the table by name. Returns nothing if the symbol
+         * can not be found.
+         *
+         * \param name Symbol name.
+         *
+         * \return Symbol from the table if found.
+         */
+        symbol_ptr lookup(const std::string& name)
+        {
+            auto entry = entries.find(name);
+
+            if (entry != entries.cend())
+            {
+                return entry->second;
+            }
+            if (this->outer_scope != nullptr)
+            {
+                return this->outer_scope->lookup(name);
+            }
+            return nothing;
+        }
+
+        /**
+         * \param name Symbol name.
+         *
+         * \return Whether the table contains a symbol with the given name.
+         */
+        bool contains(const std::string& name)
+        {
+            return lookup(name) != nothing;
+        }
+
+        /**
+         * Registers new symbol.
+         *
+         * \param name Symbol name.
+         * \param entry Symbol information.
+         *
+         * \return Whether the insertion took place.
+         */
+        bool enter(const std::string& name, symbol_ptr entry)
+        {
+            return lookup(name) == nothing && entries.insert({ name, entry }).second;
+        }
+
+        /**
+         * Returns the outer scope or nullptr if the this is the global scope.
+         *
+         * \return Outer scope.
+         */
+        std::shared_ptr<symbol_map> scope()
+        {
+            return this->outer_scope;
+        }
+    };
+
+    using symbol_table = symbol_map<std::shared_ptr<info>, std::nullptr_t, nullptr>;
+    using forward_table = std::unordered_map<std::string, std::shared_ptr<alias_type>>;
+
+    class type_info : public info
+    {
+    public:
+        const type symbol;
+
+        explicit type_info(const type symbol);
+        std::shared_ptr<type_info> is_type() override;
+    };
+
+    /**
+     * Procedure symbol information.
+     */
+    class procedure_info : public info
+    {
+    public:
+        /// Procedure type.
+        const procedure_type symbol;
+
+        /// Parameter names.
+        const std::vector<std::string> names;
+
+        /// Local definitions.
+        std::shared_ptr<symbol_table> scope;
+
+        /**
+         * Constructs procedure symbol information.
+         *
+         * \param symbol Procedure type.
+         * \param names Parameter names.
+         * \param scope Local definition (is `nullptr` for extern symbols).
+         */
+        procedure_info(const procedure_type symbol, const std::vector<std::string> names,
+                std::shared_ptr<symbol_table> scope = nullptr);
+
+        std::shared_ptr<procedure_info> is_procedure() override;
+
+        /**
+         * \return Whether this is an extern symbol.
+         */
+        bool is_extern() const;
+    };
+
+    class constant_info : public info
+    {
+    public:
+        using variant = typename
+            std::variant<std::int32_t, std::uint32_t, double, bool, unsigned char, std::nullptr_t, std::string>;
+
+        const variant symbol;
+
+        explicit constant_info(const variant& symbol);
+        std::shared_ptr<constant_info> is_constant() override;
+    };
+
+    /**
+     * Variable symbol information.
+     */
+    class variable_info : public info
+    {
+    public:
+        /// Variable type.
+        const type symbol;
+
+        /// Whether this is an extern symbol.
+        const bool is_extern;
+
+        /**
+         * Constructs a variable symbol information.
+         *
+         * \param symbol Variable type.
+         * \param is_extern Whether this is an extern symbol.
+         */
+        variable_info(const type symbol, bool is_extern);
+
+        std::shared_ptr<variable_info> is_variable() override;
+    };
+
+    std::shared_ptr<symbol_table> builtin_symbol_table();
+
+    /**
+     * Symbol bag contains:
+     *
+     * - the symbol table of a module itself
+     * - symbol tables of imported modules
+     * - forward declarations
+     */
+    class symbol_bag
+    {
+        std::shared_ptr<symbol_table> symbols;
+        std::forward_list<std::shared_ptr<symbol_table>> imports;
+        forward_table unresolved;
+
+    public:
+
+        /**
+         * \param unresolved Forward declarations collected in the previous step.
+         * \param global_table Global symbols.
+         */
+        symbol_bag(forward_table&& unresolved, std::shared_ptr<symbol_table> global_table);
+
+        /**
+         * Looks up a symbol in the current and imported modules.
+         *
+         * \param name Symbol name to look up.
+         *
+         * \return Symbol from one of the symbol tables if found.
+         */
+        std::shared_ptr<info> lookup(const std::string& name);
+
+        /**
+         * Inserts a symbol into the current scope.
+         *
+         * \param name Symbol name.
+         * \param entry Symbol info.
+         *
+         * \return Whether the insertion took place.
+         */
+        bool enter(const std::string& name, std::shared_ptr<info> entry);
+
+        /**
+         * Enters a new scope.
+         *
+         * \return Reference to the allocated scope.
+         */
+        std::shared_ptr<symbol_table> enter();
+
+        /**
+         * Sets the current scope to \a child.
+         *
+         * \param child New scope.
+         */
+        void enter(std::shared_ptr<symbol_table> child);
+
+        /**
+         * Leave the current scope.
+         *
+         * \return Left scope.
+         */
+        std::shared_ptr<symbol_table> leave();
+
+        /**
+         * Checks whether there is a forward declaration \a symbol_name and
+         * returns it if so.
+         *
+         * \param symbol_name Type name to look up.
+         * \return Forward declaration or `nullptr` if the symbol is not declared.
+         */
+        std::shared_ptr<alias_type> declared(const std::string& symbol_name);
+
+        /**
+         * Completes the forward-declared type \a symbol_name and defines it to
+         * be \a resolution.
+         *
+         * \param symbol_name Type name.
+         * \param resolution Type definition.
+         * \return Alias to the defined type.
+         */
+        std::shared_ptr<alias_type> resolve(const std::string& symbol_name, type& resolution);
+
+        /**
+         * Add imported symbols to the scope.
+         *
+         * \param bag Symbol bag of another module.
+         */
+        void add_import(const symbol_bag& bag);
+    };
+}

include/elna/gcc/elna-builtins.h

@@ -0,0 +1,41 @@
+/* Builtin definitions.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#include <memory>
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "tree-iterator.h"
+
+#include "elna/gcc/elna-tree.h"
+
+namespace elna::gcc
+{
+    void init_ttree();
+    std::shared_ptr<symbol_table> builtin_symbol_table();
+
+    void rewrite_symbol_table(std::shared_ptr<frontend::symbol_table> info_table, std::shared_ptr<symbol_table> symbols);
+    tree handle_symbol(const std::string& symbol_name, std::shared_ptr<frontend::alias_type> reference,
+            std::shared_ptr<symbol_table> symbols);
+    tree get_inner_alias(const frontend::type& type, std::shared_ptr<symbol_table> symbols);
+    void declare_procedure(const std::string& name, const frontend::procedure_info& info,
+            std::shared_ptr<symbol_table> symbols);
+    tree declare_variable(const std::string& name, const frontend::variable_info& info,
+            std::shared_ptr<symbol_table> symbols);
+}

include/elna/gcc/elna-diagnostic.h

@@ -0,0 +1,46 @@
+/* Elna frontend specific diagnostic routines.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "input.h"
+#include "tree.h"
+#include "diagnostic.h"
+
+#include <deque>
+#include <memory>
+
+#include "elna/frontend/result.h"
+
+namespace elna::gcc
+{
+    struct linemap_guard
+    {
+        explicit linemap_guard(const char *filename);
+        linemap_guard(const linemap_guard&) = delete;
+        linemap_guard(linemap_guard&&) = delete;
+
+        ~linemap_guard();
+    };
+
+    location_t get_location(const frontend::position *position);
+    std::string print_type(tree type);
+    void report_errors(const std::deque<std::unique_ptr<frontend::error>>& errors);
+}

include/elna/gcc/elna-generic.h

@@ -0,0 +1,97 @@
+/* Visitor generating a GENERIC tree.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include "elna/frontend/ast.h"
+#include "elna/frontend/symbol.h"
+#include "elna/frontend/semantic.h"
+#include "elna/gcc/elna-tree.h"
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "tree-iterator.h"
+
+#include <string>
+#include <forward_list>
+
+namespace elna::gcc
+{
+    class generic_visitor final : public frontend::empty_visitor
+    {
+        tree current_expression{ NULL_TREE };
+        elna::frontend::symbol_bag bag;
+        std::shared_ptr<symbol_table> symbols;
+
+        void enter_scope();
+        tree leave_scope();
+
+        void make_if_branch(frontend::conditional_statements& branch, tree goto_endif);
+
+        tree build_arithmetic_operation(frontend::binary_expression *expression,
+                tree_code operator_code, tree left, tree right);
+        tree build_comparison_operation(frontend::binary_expression *expression,
+                tree_code operator_code, tree left, tree right);
+        tree build_bit_logic_operation(frontend::binary_expression *expression, tree left, tree right);
+        tree build_equality_operation(frontend::binary_expression *expression, tree left, tree right);
+        void build_procedure_call(location_t call_location,
+                tree procedure_address, const std::vector<frontend::expression *>& arguments);
+        void build_record_call(location_t call_location,
+                tree symbol, const std::vector<frontend::expression *>& arguments);
+        bool build_builtin_procedures(frontend::procedure_call *call);
+        void build_assert_builtin(location_t call_location, const std::vector<frontend::expression *>& arguments);
+
+        bool expect_trait_type_only(frontend::traits_expression *trait);
+        bool expect_trait_for_integral_type(frontend::traits_expression *trait);
+        void visit_statements(const std::vector<frontend::statement *>& statements);
+        bool assert_constant(location_t expression_location);
+
+    public:
+        generic_visitor(std::shared_ptr<symbol_table> symbol_table, elna::frontend::symbol_bag bag);
+
+        void visit(frontend::program *program) override;
+        void visit(frontend::procedure_declaration *definition) override;
+        void visit(frontend::procedure_call *call) override;
+        void visit(frontend::cast_expression *expression) override;
+        void visit(frontend::traits_expression *trait) override;
+        void visit(frontend::literal<std::int32_t> *literal) override;
+        void visit(frontend::literal<std::uint32_t> *literal) override;
+        void visit(frontend::literal<double> *literal) override;
+        void visit(frontend::literal<bool> *boolean) override;
+        void visit(frontend::literal<unsigned char> *character) override;
+        void visit(frontend::literal<std::nullptr_t> *) override;
+        void visit(frontend::literal<std::string> *string) override;
+        void visit(frontend::binary_expression *expression) override;
+        void visit(frontend::unary_expression *expression) override;
+        void visit(frontend::constant_declaration *definition) override;
+        void visit(frontend::variable_declaration *declaration) override;
+        void visit(frontend::variable_expression *expression) override;
+        void visit(frontend::array_access_expression *expression) override;
+        void visit(frontend::field_access_expression *expression) override;
+        void visit(frontend::dereference_expression *expression) override;
+        void visit(frontend::unit *unit) override;
+        void visit(frontend::assign_statement *statement) override;
+        void visit(frontend::if_statement *statement) override;
+        void visit(frontend::import_declaration *) override;
+        void visit(frontend::while_statement *statement) override;
+        void visit(frontend::return_statement *statement) override;
+        void visit(frontend::defer_statement *statement) override;
+        void visit(frontend::case_statement *statement) override;
+    };
+}

include/elna/gcc/elna-tree.h

@@ -0,0 +1,105 @@
+/* Utilities to manipulate GCC trees.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+#include <forward_list>
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "tree.h"
+#include "tree-iterator.h"
+#include "stringpool.h"
+#include "fold-const.h"
+
+#include "elna/frontend/ast.h"
+#include "elna/frontend/symbol.h"
+#include "elna/gcc/elna1.h"
+
+namespace elna::gcc
+{
+    using symbol_table = frontend::symbol_map<tree, tree, NULL_TREE>;
+
+    bool is_integral_type(tree type);
+    bool is_numeric_type(tree type);
+    bool is_unique_type(tree type);
+    bool is_void_type(tree type);
+
+    /**
+     * \param type The type to evaluate.
+     * \return Whether this type can be converted to another type.
+     */
+    bool is_castable_type(tree type);
+
+    /**
+     * \param lhs Left hand value.
+     * \param rhs Right hand value.
+     * \return Whether rhs can be assigned to lhs.
+     */
+    bool are_compatible_pointers(tree lhs_type, tree rhs);
+
+    /**
+     * Prepares a value to be bound to a variable or parameter.
+     *
+     * If rvalue is a procedure declaration, builds a procedure pointer.
+     *
+     * \param rvalue Value to be assigned.
+     * \return Processed value.
+     */
+    tree prepare_rvalue(tree rvalue);
+
+    /**
+     * \param assignee Assignee.
+     * \param assignee Assignment.
+     * \return Whether an expression assignment can be assigned to a variable of type assignee.
+     */
+    bool is_assignable_from(tree assignee, tree assignment);
+
+    void append_statement(tree statement_tree);
+    void defer(tree statement_tree);
+    tree chain_defer();
+
+    tree do_pointer_arithmetic(frontend::binary_operator binary_operator,
+            tree left, tree right, location_t expression_location);
+    tree build_binary_operation(bool condition, frontend::binary_expression *expression,
+            tree_code operator_code, tree left, tree right, tree target_type);
+    tree build_arithmetic_operation(frontend::binary_expression *expression,
+            tree_code operator_code, tree left, tree right);
+    tree build_field(location_t location, tree record_type, const std::string name, tree type);
+    tree find_field_by_name(location_t expression_location, tree type, const std::string& field_name);
+    tree build_global_pointer_type(tree type);
+    tree build_static_array_type(tree type, const std::uint64_t size);
+    tree build_enumeration_type(const std::vector<std::string>& members);
+    tree build_label_decl(const char *name, location_t loc);
+
+    tree extract_constant(tree expression);
+
+    template<typename... Args>
+    tree call_built_in(location_t call_location, const char *name, tree return_type, Args... arguments)
+    {
+        tree *builtin = elna_global_decls->get(name);
+        gcc_assert(builtin != nullptr);
+
+        tree fndecl_type = build_function_type(return_type, TYPE_ARG_TYPES(*builtin));
+        tree builtin_addr = build1_loc(call_location, ADDR_EXPR, build_pointer_type(fndecl_type), *builtin);
+
+        tree argument_trees[sizeof...(Args)] = {arguments...};
+
+        return fold_build_call_array(return_type, builtin_addr, sizeof...(Args), argument_trees);
+    }
+}

include/elna/gcc/elna1.h

@@ -0,0 +1,94 @@
+/* Language-dependent hooks for Elna.
+   Copyright (C) 2025 Free Software Foundation, Inc.
+
+GCC is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 3, or (at your option)
+any later version.
+
+GCC is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#pragma once
+
+enum elna_tree_index
+{
+    ELNA_TI_INT_TYPE,
+    ELNA_TI_WORD_TYPE,
+    ELNA_TI_CHAR_TYPE,
+    ELNA_TI_BOOL_TYPE,
+    ELNA_TI_POINTER_TYPE,
+    ELNA_TI_FLOAT_TYPE,
+    ELNA_TI_STRING_TYPE,
+    ELNA_TI_BOOL_TRUE,
+    ELNA_TI_BOOL_FALSE,
+    ELNA_TI_POINTER_NIL,
+    ELNA_TI_STRING_PTR_FIELD,
+    ELNA_TI_STRING_LENGTH_FIELD,
+    ELNA_TI_MAX
+};
+
+extern GTY(()) tree elna_global_trees[ELNA_TI_MAX];
+extern GTY(()) hash_map<nofree_string_hash, tree> *elna_global_decls;
+
+#define elna_int_type_node elna_global_trees[ELNA_TI_INT_TYPE]
+#define elna_word_type_node elna_global_trees[ELNA_TI_WORD_TYPE]
+#define elna_char_type_node elna_global_trees[ELNA_TI_CHAR_TYPE]
+#define elna_bool_type_node elna_global_trees[ELNA_TI_BOOL_TYPE]
+#define elna_pointer_type_node elna_global_trees[ELNA_TI_POINTER_TYPE]
+#define elna_float_type_node elna_global_trees[ELNA_TI_FLOAT_TYPE]
+#define elna_string_type_node elna_global_trees[ELNA_TI_STRING_TYPE]
+#define elna_bool_true_node elna_global_trees[ELNA_TI_BOOL_TRUE]
+#define elna_bool_false_node elna_global_trees[ELNA_TI_BOOL_FALSE]
+#define elna_pointer_nil_node elna_global_trees[ELNA_TI_POINTER_NIL]
+#define elna_string_ptr_field_node elna_global_trees[ELNA_TI_STRING_PTR_FIELD]
+#define elna_string_length_field_node elna_global_trees[ELNA_TI_STRING_LENGTH_FIELD]
+
+/* Language-dependent contents of a type. */
+struct GTY (()) lang_type
+{
+};
+
+/* Language-dependent contents of a decl. */
+struct GTY (()) lang_decl
+{
+};
+
+struct GTY (()) defer_scope
+{
+    tree defer_block;
+    tree try_statements;
+};
+
+struct GTY ((chain_next ("%h.level_chain"))) binding_level
+{
+    // A block chain is needed to call defer statements beloning to each block.
+    tree blocks;
+
+    // Parent level.
+    struct binding_level *level_chain;
+
+    // Statements before the first defer has been seen.
+    tree statement_list;
+
+    // Defer statement coupled with statements following it.
+    vec<defer_scope, va_gc> *defers;
+};
+
+struct GTY (()) language_function
+{
+    // Local variables and constants.
+    tree names;
+
+    // Lexical scope.
+    struct binding_level *binding_level;
+};
+
+#define f_binding_level DECL_STRUCT_FUNCTION(current_function_decl)->language->binding_level
+#define f_names DECL_STRUCT_FUNCTION(current_function_decl)->language->names

rakelib/gcc.rake

@@ -0,0 +1,113 @@
+# This Source Code Form is subject to the terms of the Mozilla Public License,
+# v. 2.0. If a copy of the MPL was not distributed with this file, You can
+# obtain one at https://mozilla.org/MPL/2.0/. -}
+# frozen_string_literal: true
+
+require 'uri'
+require 'net/http'
+require 'open3'
+require 'pathname'
+
+def gcc_verbose(gcc_binary)
+  read, write = IO.pipe
+  sh({'LANG' => 'C'}, gcc_binary, '--verbose', err: write)
+  write.close
+  output = read.read
+  read.close
+  output
+end
+
+def find_build_target
+  gcc_verbose(ENV.fetch 'CC', 'gcc')
+    .lines
+    .find { |line| line.start_with? 'Target: ' }
+    .split(' ')
+    .last
+    .strip
+end
+
+def download_and_pipe(url, target, command)
+  target.mkpath
+
+  Net::HTTP.start(url.host, url.port, use_ssl: url.scheme == 'https') do |http|
+    request = Net::HTTP::Get.new url.request_uri
+
+    http.request request do |response|
+      case response
+      when Net::HTTPRedirection
+        download_and_pipe URI.parse(response['location']), target, command
+      when Net::HTTPSuccess
+        Dir.chdir target.to_path do
+          Open3.popen2(*command) do |stdin, stdout, wait_thread|
+            Thread.new do
+              stdout.each { |line| puts line }
+            end
+
+            response.read_body do |chunk|
+              stdin.write chunk
+            end
+            stdin.close
+
+            wait_thread.value
+          end
+        end
+      else
+        response.error!
+      end
+    end
+  end
+end
+
+namespace :gcc do
+  # Dependencies.
+  GCC_VERSION = "15.2.0"
+  HOST_GCC = 'build/host/gcc'
+  HOST_INSTALL = 'build/host/install'
+  GCC_PATCH = 'https://raw.githubusercontent.com/Homebrew/formula-patches/575ffcaed6d3112916fed77d271dd3799a7255c4/gcc/gcc-15.1.0.diff'
+
+  directory HOST_GCC
+  directory HOST_INSTALL
+  directory 'build/tools'
+
+  desc 'Download and configure the bootstrap compiler'
+  task configure: ['build/tools', HOST_GCC, HOST_INSTALL] do
+    url = URI.parse "https://gcc.gnu.org/pub/gcc/releases/gcc-#{GCC_VERSION}/gcc-#{GCC_VERSION}.tar.xz"
+    build_target = find_build_target
+    source_directory = Pathname.new "build/tools/gcc-#{GCC_VERSION}"
+    frontend_link = source_directory + 'gcc'
+
+    download_and_pipe url, source_directory.dirname, ['tar', '-Jxv']
+    download_and_pipe URI.parse(GCC_PATCH), source_directory, ['patch', '-p1']
+
+    sh 'contrib/download_prerequisites', chdir: source_directory.to_path
+    File.symlink Pathname.new('.').relative_path_from(frontend_link), (frontend_link + 'elna')
+
+    configure_options = [
+      "--prefix=#{File.realpath HOST_INSTALL}",
+      '--enable-languages=c,c++,elna',
+      '--disable-bootstrap',
+      '--disable-multilib',
+      '--with-system-zlib',
+      "--target=#{build_target}",
+      "--build=#{build_target}",
+      "--host=#{build_target}"
+    ]
+    if File.symlink? '/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk'
+      configure_options << '--with-sysroot=/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk'
+    end
+    env = ENV.slice 'CC', 'CXX'
+    env['CFLAGS'] = env['CXXFLAGS'] = '-O0 -g -fPIC -I/opt/homebrew/opt/flex/include'
+
+    configure = source_directory.relative_path_from(HOST_GCC) + 'configure'
+    sh env, configure.to_path, *configure_options, chdir: HOST_GCC
+  end
+
+  desc 'Make and install the bootstrap compiler'
+  task :make do
+    sh 'make', '-j', Etc.nprocessors.to_s, chdir: HOST_GCC
+    sh 'make', 'install', chdir: HOST_GCC
+  end
+end
+
+desc 'Build the bootstrap compiler'
+task gcc: %w[gcc:configure gcc:make]

rakelib/modula.rake

@@ -0,0 +1,36 @@
+# This Source Code Form is subject to the terms of the Mozilla Public License,
+# v. 2.0. If a copy of the MPL was not distributed with this file, You can
+# obtain one at https://mozilla.org/MPL/2.0/. -}
+# frozen_string_literal: true
+
+require 'pathname'
+require 'rake/clean'
+
+CLEAN.include 'build/gcc'
+
+task source: ['source/main.elna', 'build/gcc/elna'] do |t|
+  sources, compiler  = t.prerequisites.partition { |f| f.end_with? '.elna' }
+
+  sh *compiler, '--parse', *sources
+end
+
+rule(/gcc\/.+\.o$/ => ->(file) {
+  source = Pathname.new('source') +
+    Pathname.new(file).relative_path_from('build/gcc').sub_ext('.elna')
+
+  ['build/host/install/bin/gelna', source]
+}) do |t|
+  Pathname.new(t.name).dirname.mkpath
+  sources, compiler = t.prerequisites.partition { |source| source.end_with? '.elna' }
+
+  sh *compiler, '-c', '-O0', '-g', '-o', t.name, *sources
+end
+
+file 'build/gcc/elna' => FileList['source/**/*.elna'].reject { |file|
+  file != file.downcase
+}.map { |file|
+  Pathname.new('build/gcc') +
+    Pathname.new(file).relative_path_from('source').sub_ext('.o')
+} do |t|
+  sh 'build/host/install/bin/gcc', '-o', t.name, *t.prerequisites
+end

source/CommandLineInterface.def

@@ -0,0 +1,16 @@
+DEFINITION MODULE CommandLineInterface;
+
+FROM Common IMPORT ShortString;
+
+TYPE
+  CommandLine = RECORD
+    input: ShortString;
+    output: ShortString;
+    lex: BOOLEAN;
+    parse: BOOLEAN
+  END;
+  PCommandLine = POINTER TO CommandLine;
+
+PROCEDURE parse_command_line(): PCommandLine;
+
+END CommandLineInterface.

source/Common.def

@@ -0,0 +1,12 @@
+DEFINITION MODULE Common;
+
+TYPE
+  ShortString = ARRAY[1..256] OF CHAR;
+  Identifier = ARRAY[1..256] OF CHAR;
+  PIdentifier = POINTER TO Identifier;
+  TextLocation = RECORD
+    line: CARDINAL;
+    column: CARDINAL
+  END;
+
+END Common.

source/Lexer.def

@@ -0,0 +1,107 @@
+DEFINITION MODULE Lexer;
+
+FROM FIO IMPORT File;
+
+FROM Common IMPORT Identifier, ShortString, TextLocation;
+
+TYPE
+  PLexerBuffer = POINTER TO CHAR;
+  BufferPosition = RECORD
+    iterator: PLexerBuffer;
+    location: TextLocation
+  END;
+  PBufferPosition = POINTER TO BufferPosition;
+  Lexer = RECORD
+    input: File;
+    buffer: PLexerBuffer;
+    size: CARDINAL;
+    length: CARDINAL;
+    start: BufferPosition;
+    current: BufferPosition
+  END;
+  PLexer = POINTER TO Lexer;
+  LexerKind = (
+    lexerKindEof,
+    lexerKindIdentifier,
+    lexerKindIf,
+    lexerKindThen,
+    lexerKindElse,
+    lexerKindElsif,
+    lexerKindWhile,
+    lexerKindDo,
+    lexerKindProc,
+    lexerKindBegin,
+    lexerKindEnd,
+    lexerKindXor,
+    lexerKindConst,
+    lexerKindVar,
+    lexerKindCase,
+    lexerKindOf,
+    lexerKindType,
+    lexerKindRecord,
+    lexerKindUnion,
+    lexerKindPipe,
+    lexerKindTo,
+    lexerKindBoolean,
+    lexerKindNull,
+    lexerKindAnd,
+    lexerKindOr,
+    lexerKindTilde,
+    lexerKindReturn,
+    lexerKindDefer,
+    lexerKindRange,
+    lexerKindLeftParen,
+    lexerKindRightParen,
+    lexerKindLeftSquare,
+    lexerKindRightSquare,
+    lexerKindGreaterEqual,
+    lexerKindLessEqual,
+    lexerKindGreaterThan,
+    lexerKindLessThan,
+    lexerKindNotEqual,
+    lexerKindEqual,
+    lexerKindSemicolon,
+    lexerKindDot,
+    lexerKindComma,
+    lexerKindPlus,
+    lexerKindMinus,
+    lexerKindAsterisk,
+    lexerKindDivision,
+    lexerKindRemainder,
+    lexerKindAssignment,
+    lexerKindColon,
+    lexerKindHat,
+    lexerKindAt,
+    lexerKindComment,
+    lexerKindInteger,
+    lexerKindWord,
+    lexerKindCharacter,
+    lexerKindString,
+    lexerKindFrom,
+    lexerKindPointer,
+    lexerKindArray,
+    lexerKindArrow,
+    lexerKindProgram,
+    lexerKindModule,
+    lexerKindImport
+  );
+  LexerToken = RECORD
+    CASE kind: LexerKind OF
+      lexerKindBoolean: booleanKind: BOOLEAN |
+      lexerKindIdentifier: identifierKind: Identifier |
+      lexerKindInteger: integerKind: INTEGER |
+      lexerKindString: stringKind: ShortString
+    END;
+    start_location: TextLocation;
+    end_location: TextLocation
+  END;
+  PLexerToken = POINTER TO LexerToken;
+
+PROCEDURE lexer_initialize(lexer: PLexer; input: File);
+PROCEDURE lexer_destroy(lexer: PLexer);
+(* Returns the last read token. *)
+PROCEDURE lexer_current(lexer: PLexer): LexerToken;
+(* Read and return the next token. *)
+PROCEDURE lexer_lex(lexer: PLexer): LexerToken;
+
+END Lexer.

source/Parser.def

@@ -0,0 +1,200 @@
+DEFINITION MODULE Parser;
+
+FROM Common IMPORT Identifier, PIdentifier, ShortString;
+FROM Lexer IMPORT PLexer;
+
+TYPE
+  Parser = RECORD
+    lexer: PLexer
+  END;
+  PParser = POINTER TO Parser;
+
+  AstLiteralKind = (
+    astLiteralKindInteger,
+    astLiteralKindString,
+    astLiteralKindNull,
+    astLiteralKindBoolean
+  );
+  AstLiteral = RECORD
+    CASE kind: AstLiteralKind OF
+      astLiteralKindInteger: integer: INTEGER |
+      astLiteralKindString: string: ShortString |
+      astLiteralKindNull: |
+      astLiteralKindBoolean: boolean: BOOLEAN
+    END
+  END;
+  PAstLiteral = POINTER TO AstLiteral;
+
+  AstUnaryOperator = (
+    astUnaryOperatorReference,
+    astUnaryOperatorNot,
+    astUnaryOperatorMinus
+  );
+  AstBinaryOperator = (
+    astBinaryOperatorSum,
+    astBinaryOperatorSubtraction,
+    astBinaryOperatorMultiplication,
+    astBinaryOperatorDivision,
+    astBinaryOperatorRemainder,
+    astBinaryOperatorEquals,
+    astBinaryOperatorNotEquals,
+    astBinaryOperatorLess,
+    astBinaryOperatorGreater,
+    astBinaryOperatorLessEqual,
+    astBinaryOperatorGreaterEqual,
+    astBinaryOperatorDisjunction,
+    astBinaryOperatorConjunction,
+    astBinaryOperatorExclusiveDisjunction,
+    astBinaryOperatorShiftLeft,
+    astBinaryOperatorShiftRight
+  );
+
+  AstExpressionKind = (
+    astExpressionKindLiteral,
+    astExpressionKindIdentifier,
+    astExpressionKindArrayAccess,
+    astExpressionKindDereference,
+    astExpressionKindFieldAccess,
+    astExpressionKindUnary,
+    astExpressionKindBinary,
+    astExpressionKindCall
+  );
+  AstExpression = RECORD 
+    CASE kind: AstExpressionKind OF
+      astExpressionKindLiteral: literal: PAstLiteral |
+      astExpressionKindIdentifier: identifier: Identifier |
+      astExpressionKindDereference: reference: PAstExpression |
+      astExpressionKindArrayAccess:
+        array: PAstExpression;
+        index: PAstExpression |
+      astExpressionKindFieldAccess:
+        aggregate: PAstExpression;
+        field: Identifier |
+      astExpressionKindUnary:
+        unary_operator: AstUnaryOperator;
+        unary_operand: PAstExpression |
+      astExpressionKindBinary:
+        binary_operator: AstBinaryOperator;
+        lhs: PAstExpression;
+        rhs: PAstExpression |
+      astExpressionKindCall:
+        callable: PAstExpression;
+        argument_count: CARDINAL;
+        arguments: PPAstExpression
+    END
+  END;
+  PAstExpression = POINTER TO AstExpression;
+  PPAstExpression = POINTER TO PAstExpression;
+
+  AstStatementKind = (
+    astStatementKindIf,
+    astStatementKindWhile,
+    astStatementKindAssignment,
+    astStatementKindReturn,
+    astStatementKindCall
+  );
+  AstStatement = RECORD
+    CASE kind: AstStatementKind OF
+      astStatementKindIf:
+        if_condition: PAstExpression;
+        if_branch: AstCompoundStatement |
+      astStatementKindWhile:
+        while_condition: PAstExpression;
+        while_body: AstCompoundStatement |
+      astStatementKindAssignment:
+        assignee: PAstExpression;
+        assignment: PAstExpression |
+      astStatementKindReturn: returned: PAstExpression |
+      astStatementKindCall: call: PAstExpression
+    END
+  END;
+  PAstStatement = POINTER TO AstStatement;
+  PPAstStatement = POINTER TO PAstStatement;
+  AstCompoundStatement = RECORD
+    count: CARDINAL;
+    statements: PPAstStatement
+  END;
+
+  AstImportStatement = RECORD
+    package: Identifier;
+    symbols: PIdentifier
+  END;
+  PAstImportStatement = POINTER TO AstImportStatement;
+  PPAstImportStatement = POINTER TO PAstImportStatement;
+
+  AstConstantDeclaration = RECORD
+    constant_name: Identifier;
+    constant_value: INTEGER
+  END;
+  PAstConstantDeclaration = POINTER TO AstConstantDeclaration;
+  PPAstConstantDeclaration = POINTER TO PAstConstantDeclaration;
+
+  AstFieldDeclaration = RECORD
+    field_name: Identifier;
+    field_type: PAstTypeExpression
+  END;
+  PAstFieldDeclaration = POINTER TO AstFieldDeclaration;
+
+  AstTypeExpressionKind = (
+    astTypeExpressionKindNamed,
+    astTypeExpressionKindRecord,
+    astTypeExpressionKindEnumeration,
+    astTypeExpressionKindArray,
+    astTypeExpressionKindPointer,
+    astTypeExpressionKindProcedure
+  );
+  AstTypeExpression = RECORD
+    CASE kind: AstTypeExpressionKind OF
+      astTypeExpressionKindNamed: name: Identifier |
+      astTypeExpressionKindEnumeration: cases: PIdentifier |
+      astTypeExpressionKindPointer: target: PAstTypeExpression |
+      astTypeExpressionKindRecord: fields: PAstFieldDeclaration |
+      astTypeExpressionKindArray:
+        base: PAstTypeExpression;
+        length: CARDINAL |
+      astTypeExpressionKindProcedure: parameters: PPAstTypeExpression
+    END
+  END;
+  PAstTypeExpression = POINTER TO AstTypeExpression;
+  PPAstTypeExpression = POINTER TO PAstTypeExpression;
+
+  AstTypedDeclaration = RECORD
+    identifier: Identifier;
+    type_expression: PAstTypeExpression
+  END;
+  PAstTypedDeclaration = POINTER TO AstTypedDeclaration;
+  PPAstTypedDeclaration = POINTER TO PAstTypedDeclaration;
+
+  AstVariableDeclaration = RECORD
+    variable_name: Identifier;
+    variable_type: PAstTypeExpression
+  END;
+  PAstVariableDeclaration = POINTER TO AstVariableDeclaration;
+  PPAstVariableDeclaration = POINTER TO PAstVariableDeclaration;
+
+  AstProcedureDeclaration = RECORD
+    name: Identifier;
+    parameter_count: CARDINAL;
+    parameters: PAstTypedDeclaration;
+    return_type: PAstTypeExpression;
+    constants: PPAstConstantDeclaration;
+    variables: PPAstVariableDeclaration;
+    statements: AstCompoundStatement
+  END;
+  PAstProcedureDeclaration = POINTER TO AstProcedureDeclaration;
+  PPAstProcedureDeclaration = POINTER TO PAstProcedureDeclaration;
+
+  AstModule = RECORD
+    main: BOOLEAN;
+    imports: PPAstImportStatement;
+    constants: PPAstConstantDeclaration;
+    types: PPAstTypedDeclaration;
+    variables: PPAstVariableDeclaration;
+    procedures: PPAstProcedureDeclaration;
+    statements: AstCompoundStatement
+  END;
+  PAstModule = POINTER TO AstModule;
+
+PROCEDURE parse(lexer: PLexer): PAstModule;
+
+END Parser.

source/Transpiler.def

@@ -0,0 +1,20 @@
+DEFINITION MODULE Transpiler;
+
+FROM FIO IMPORT File;
+
+FROM Common IMPORT ShortString;
+FROM Lexer IMPORT PLexer, Lexer;
+FROM Parser IMPORT PAstModule;
+
+TYPE
+  TranspilerContext = RECORD
+    input_name: ShortString;
+    output: File;
+    definition: File;
+    indentation: CARDINAL
+  END;
+  PTranspilerContext = POINTER TO TranspilerContext;
+
+PROCEDURE transpile(ast_module: PAstModule; output: File; definition: File; input_name: ShortString);
+
+END Transpiler.

source/Transpiler.elna

@@ -0,0 +1,631 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+from FIO import File, WriteNBytes, WriteLine, WriteChar, WriteString;
+from NumberIO import IntToStr;
+
+import common, Parser;
+
+type
+  TranspilerContext* = record
+    input_name: String;
+    output: File;
+    definition: File;
+    indentation: Word
+  end;
+
+proc indent(context: ^TranspilerContext);
+var
+  count: Word;
+begin
+  count := 0;
+
+  while count < context^.indentation do
+    WriteString(context^.output, "  ");
+    count := count + 1u
+  end
+end;
+
+(* Write a semicolon followed by a newline. *)
+proc write_semicolon(output: File);
+begin
+  WriteChar(output, ';');
+  WriteLine(output)
+end;
+
+proc transpile_import_statement(context: ^TranspilerContext, import_statement: ^AstImportStatement);
+var
+  current_symbol: ^Identifier;
+begin
+  WriteString(context^.output, "FROM ");
+  transpile_identifier(context, import_statement^.package);
+
+  WriteString(context^.output, " IMPORT ");
+
+  current_symbol := import_statement^.symbols;
+  transpile_identifier(context, current_symbol^);
+  current_symbol := current_symbol + 1;
+
+  while current_symbol^[1] <> '\0' do
+    WriteString(context^.output, ", ");
+    transpile_identifier(context, current_symbol^);
+    current_symbol := current_symbol + 1;
+  end;
+  write_semicolon(context^.output)
+end;
+
+proc transpile_import_part(context: ^TranspilerContext, imports: ^^AstImportStatement);
+var
+  import_statement: ^AstImportStatement;
+begin
+  while imports^ <> nil do
+    transpile_import_statement(context, imports^);
+    imports := imports + 1
+  end;
+  WriteLine(context^.output)
+end;
+
+proc transpile_constant_declaration(context: ^TranspilerContext, declaration: ^AstConstantDeclaration);
+var
+  buffer: [20]Char;
+begin
+  WriteString(context^.output, "  ");
+  transpile_identifier(context, declaration^.constant_name);
+
+  WriteString(context^.output, " = ");
+
+  IntToStr(declaration^.constant_value, 0, buffer);
+  WriteString(context^.output, buffer);
+
+  write_semicolon(context^.output)
+end;
+
+proc transpile_constant_part(context: ^TranspilerContext, declarations: ^^AstConstantDeclaration, extra_newline: Bool);
+var
+  current_declaration: ^^AstConstantDeclaration;
+begin
+  if declarations^ <> nil then
+    WriteString(context^.output, "CONST");
+    WriteLine(context^.output);
+
+    current_declaration := declarations;
+    while current_declaration^ <> nil do
+      transpile_constant_declaration(context, current_declaration^);
+
+      current_declaration := current_declaration + 1
+    end;
+    if extra_newline then
+      WriteLine(context^.output)
+    end
+  end
+end;
+
+proc transpile_module(context: ^TranspilerContext, result: ^AstModule);
+begin
+  if result^.main = false then
+    WriteString(context^.output, "IMPLEMENTATION ")
+  end;
+  WriteString(context^.output, "MODULE ");
+
+  (* Write the module name and end the line with a semicolon and newline. *)
+  transpile_module_name(context);
+
+  write_semicolon(context^.output);
+  WriteLine(context^.output);
+
+  (* Write the module body. *)
+
+  transpile_import_part(context, result^.imports);
+  transpile_constant_part(context, result^.constants, true);
+  transpile_type_part(context, result^.types);
+  transpile_variable_part(context, result^.variables, true);
+  transpile_procedure_part(context, result^.procedures);
+  transpile_statement_part(context, result^.statements);
+
+  WriteString(context^.output, "END ");
+  transpile_module_name(context);
+
+  WriteChar(context^.output, ".");
+  WriteLine(context^.output)
+end;
+
+proc transpile_type_fields(context: ^TranspilerContext, fields: ^AstFieldDeclaration);
+var
+  current_field: ^AstFieldDeclaration;
+begin
+  current_field := fields;
+
+  while current_field^.field_name[1] <> '\0' do
+    WriteString(context^.output, "    ");
+    transpile_identifier(context, current_field^.field_name);
+
+    WriteString(context^.output, ": ");
+    transpile_type_expression(context, current_field^.field_type);
+
+    current_field := current_field + 1;
+
+    if current_field^.field_name[1] <> '\0' then
+      WriteChar(context^.output, ';')
+    end;
+    WriteLine(context^.output)
+  end
+end;
+
+proc transpile_record_type(context: ^TranspilerContext, type_expression: ^AstTypeExpression);
+begin
+  WriteString(context^.output, "RECORD");
+  WriteLine(context^.output);
+  transpile_type_fields(context, type_expression^.fields);
+  WriteString(context^.output, "  END")
+end;
+
+proc transpile_pointer_type(context: ^TranspilerContext, type_expression: ^AstTypeExpression);
+begin
+  WriteString(context^.output, "POINTER TO ");
+
+  transpile_type_expression(context, type_expression^.target)
+end;
+
+proc transpile_array_type(context: ^TranspilerContext, type_expression: ^AstTypeExpression);
+var
+  buffer: [20]Char;
+begin
+  WriteString(context^.output, "ARRAY");
+
+  if type_expression^.length <> 0 then
+    WriteString(context^.output, "[1..");
+
+    IntToStr(type_expression^.length, 0, buffer);
+    WriteString(context^.output, buffer);
+
+    WriteChar(context^.output, ']')
+  end;
+  WriteString(context^.output, " OF ");
+
+  transpile_type_expression(context, type_expression^.base)
+end;
+
+proc transpile_enumeration_type(context: ^TranspilerContext, type_expression: ^AstTypeExpression);
+var
+  current_case: ^Identifier;
+begin
+  current_case := type_expression^.cases;
+
+  WriteString(context^.output, "(");
+  WriteLine(context^.output);
+  WriteString(context^.output, "    ");
+  transpile_identifier(context, current_case^);
+  current_case := current_case + 1;
+
+  while current_case^[1] <> '\0' do
+    WriteChar(context^.output, ',');
+    WriteLine(context^.output);
+    WriteString(context^.output, "    ");
+    transpile_identifier(context, current_case^);
+
+    current_case := current_case + 1
+  end;
+  WriteLine(context^.output);
+  WriteString(context^.output, "  )")
+end;
+
+proc transpile_identifier(context: ^TranspilerContext, identifier: Identifier);
+var
+  written_bytes: Word;
+begin
+  written_bytes := WriteNBytes(context^.output, cast(identifier[1]: Word), @identifier[2])
+end;
+
+proc transpile_procedure_type(context: ^TranspilerContext, type_expression: ^AstTypeExpression);
+var
+  result: ^AstTypeExpression;
+  current_parameter: ^^AstTypeExpression;
+  parameter_count: Word;
+begin
+  WriteString(context^.output, "PROCEDURE(");
+  current_parameter := type_expression^.parameters;
+
+  while current_parameter^ <> nil do
+    transpile_type_expression(context, current_parameter^);
+
+    current_parameter := current_parameter + 1;
+
+    if current_parameter^ <> nil then
+      WriteString(context^.output, ", ")
+    end
+  end;
+  WriteChar(context^.output, ')')
+end;
+
+proc transpile_type_expression(context: ^TranspilerContext, type_expression: ^AstTypeExpression);
+begin
+  if type_expression^.kind = astTypeExpressionKindRecord then
+    transpile_record_type(context, type_expression)
+  end;
+  if type_expression^.kind = astTypeExpressionKindEnumeration then
+    transpile_enumeration_type(context, type_expression)
+  end;
+  if type_expression^.kind = astTypeExpressionKindArray then
+    transpile_array_type(context, type_expression)
+  end;
+  if type_expression^.kind = astTypeExpressionKindPointer then
+    transpile_pointer_type(context, type_expression)
+  end;
+  if type_expression^.kind = astTypeExpressionKindProcedure then
+    transpile_procedure_type(context, type_expression)
+  end;
+  if type_expression^.kind = astTypeExpressionKindNamed then
+    transpile_identifier(context, type_expression^.name)
+  end
+end;
+
+proc transpile_type_declaration(context: ^TranspilerContext, declaration: ^AstTypedDeclaration);
+var
+  written_bytes: Word;
+begin
+  WriteString(context^.output, "  ");
+
+  transpile_identifier(context^.output, declaration^.identifier);
+  WriteString(context^.output, " = ");
+
+  transpile_type_expression(context, declaration^.type_expression);
+  write_semicolon(context^.output)
+end;
+
+proc transpile_type_part(context: ^TranspilerContext, declarations: ^^AstTypedDeclaration);
+var
+  current_declaration: ^^AstTypedDeclaration;
+begin
+  if declarations^ <> nil then
+    WriteString(context^.output, "TYPE");
+    WriteLine(context^.output);
+
+    current_declaration := declarations;
+    while current_declaration^ <> nil do
+      transpile_type_declaration(context, current_declaration^);
+
+      current_declaration := current_declaration + 1
+    end;
+    WriteLine(context^.output)
+  end
+end;
+
+proc transpile_variable_declaration(context: ^TranspilerContext, declaration: ^AstVariableDeclaration);
+begin
+  WriteString(context^.output, "  ");
+  transpile_identifier(context, declaration^.variable_name);
+
+  WriteString(context^.output, ": ");
+
+  transpile_type_expression(context, declaration^.variable_type);
+  write_semicolon(context^.output)
+end;
+
+proc transpile_variable_part(context: ^TranspilerContext, declarations: ^^AstVariableDeclaration, extra_newline: Bool);
+var
+  current_declaration: ^^AstVariableDeclaration;
+begin
+  if declarations^ <> nil then
+    WriteString(context^.output, "VAR");
+    WriteLine(context^.output);
+
+    current_declaration := declarations;
+    while current_declaration^ <> nil do
+      transpile_variable_declaration(context, current_declaration^);
+
+      current_declaration := current_declaration + 1
+    end;
+    if extra_newline then
+      WriteLine(context^.output)
+    end
+  end
+end;
+
+proc transpile_procedure_heading(context: ^TranspilerContext, declaration: ^AstProcedureDeclaration);
+var
+  parameter_index: Word;
+  current_parameter: ^AstTypedDeclaration;
+begin
+  WriteString(context^.output, "PROCEDURE ");
+  transpile_identifier(context, declaration^.name);
+  WriteChar(context^.output, '(');
+
+  parameter_index := 0;
+  current_parameter := declaration^.parameters;
+
+  while parameter_index < declaration^.parameter_count do
+    transpile_identifier(context, current_parameter^.identifier);
+    WriteString(context^.output, ": ");
+    transpile_type_expression(context, current_parameter^.type_expression);
+
+    parameter_index := parameter_index + 1u;
+    current_parameter := current_parameter + 1;
+
+    if parameter_index <> declaration^.parameter_count then
+      WriteString(context^.output, "; ")
+    end
+  end;
+
+  WriteString(context^.output, ")");
+
+  (* Check for the return type and write it. *)
+  if declaration^.return_type <> nil then
+    WriteString(context^.output, ": ");
+    transpile_type_expression(context, declaration^.return_type)
+  end;
+  write_semicolon(context^.output)
+end;
+
+proc transpile_unary_operator(context: ^TranspilerContext, operator: AstUnaryOperator);
+begin
+  if operator = AstUnaryOperator.minus then
+    WriteChar(context^.output, '-')
+  end;
+  if operator = AstUnaryOperator.not then
+    WriteChar(context^.output, '~')
+  end
+end;
+
+proc transpile_binary_operator(context: ^TranspilerContext, operator: AstBinaryOperator);
+begin
+  case operator of
+  	AstBinaryOperator.sum: WriteChar(context^.output, '+')
+  	| AstBinaryOperator.subtraction: WriteChar(context^.output, '-')
+  	| AstBinaryOperator.multiplication: WriteChar(context^.output, '*')
+	| AstBinaryOperator.equals: WriteChar(context^.output, '=')
+	| AstBinaryOperator.not_equals: WriteChar(context^.output, '#')
+	| AstBinaryOperator.less: WriteChar(context^.output, '<')
+	| AstBinaryOperator.greater: WriteChar(context^.output, '>')
+  	| AstBinaryOperator.less_equal: WriteString(context^.output, "<=")
+  	| AstBinaryOperator.greater_equal: WriteString(context^.output, ">=")
+  	| AstBinaryOperator.disjunction: WriteString(context^.output, "OR")
+	| AstBinaryOperatorConjunction: WriteString(context^.output, "AND")
+  end
+end;
+
+proc transpile_expression(context: ^TranspilerContext, expression: ^AstExpression);
+var
+  literal: ^AstLiteral;
+  buffer: [20]Char;
+  argument_index: Word;
+  current_argument: ^^AstExpression;
+begin
+  if expression^.kind = astExpressionKindLiteral then
+    literal := expression^.literal;
+
+    if literal^.kind = AstLiteralKind.integer then
+      IntToStr(literal^.integer, 0, buffer);
+      WriteString(context^.output, buffer)
+    end;
+    if literal^.kind = AstLiteralKind.string then
+      WriteString(context^.output, literal^.string)
+    end;
+    if literal^.kind = AstLiteralKind.null then
+      WriteString(context^.output, "NIL")
+    end;
+    if (literal^.kind = AstLiteralKind.boolean) & literal^.boolean then
+      WriteString(context^.output, "TRUE")
+    end;
+    if (literal^.kind = AstLiteralKind.boolean) & (literal^.boolean = false) then
+      WriteString(context^.output, "FALSE")
+    end
+  end;
+  if expression^.kind = astExpressionKindIdentifier then
+    transpile_identifier(context, expression^.identifier)
+  end;
+  if expression^.kind = astExpressionKindDereference then
+    transpile_expression(context, expression^.reference);
+    WriteChar(context^.output, '^')
+  end;
+  if expression^.kind = astExpressionKindArrayAccess then
+    transpile_expression(context, expression^.array);
+    WriteChar(context^.output, '[');
+    transpile_expression(context, expression^.index);
+    WriteChar(context^.output, ']')
+  end;
+  if expression^.kind = astExpressionKindFieldAccess then
+    transpile_expression(context, expression^.aggregate);
+    WriteChar(context^.output, '.');
+    transpile_identifier(contextexpression^.field)
+  end;
+  if expression^.kind = astExpressionKindUnary then
+    transpile_unary_operator(context, expression^.unary_operator);
+    transpile_expression(context, expression^.unary_operand)
+  end;
+  if expression^.kind = astExpressionKindBinary then
+    WriteChar(context^.output, '(');
+    transpile_expression(context, expression^.lhs);
+    WriteChar(context^.output, ' ');
+    transpile_binary_operator(context, expression^.binary_operator);
+    WriteChar(context^.output, ' ');
+    transpile_expression(context, expression^.rhs);
+    WriteChar(context^.output, ')')
+  end;
+  if expression^.kind = astExpressionKindCall then
+    transpile_expression(context, expression^.callable);
+    WriteChar(context^.output, '(');
+
+    current_argument := expression^.arguments;
+    if expression^.argument_count > 0 then
+      transpile_expression(context, current_argument^);
+
+      argument_index := 1u;
+      current_argument := current_argument + 1;
+
+      while argument_index < expression^.argument_count do
+        WriteString(context^.output, ", ");
+
+        transpile_expression(context, current_argument^);
+
+        current_argument := current_argument + 1;
+        argument_index := argument_index + 1u
+      end
+    end;
+    WriteChar(context^.output, ')')
+  end
+end;
+
+proc transpile_if_statement(context: ^TranspilerContext, statement: ^AstStatement);
+begin
+  WriteString(context^.output, "IF ");
+  transpile_expression(context, statement^.if_condition);
+
+  WriteString(context^.output, " THEN");
+  WriteLine(context^.output);
+  context^.indentation := context^.indentation + 1u;
+
+  transpile_compound_statement(context, statement^.if_branch);
+  context^.indentation := context^.indentation - 1u;
+  indent(context);
+  WriteString(context^.output, "END")
+end;
+
+proc transpile_while_statement(context: ^TranspilerContext, statement: ^AstStatement);
+begin
+  WriteString(context^.output, "WHILE ");
+  transpile_expression(context, statement^.while_condition);
+
+  WriteString(context^.output, " DO");
+  WriteLine(context^.output);
+  context^.indentation := context^.indentation + 1u;
+
+  transpile_compound_statement(context, statement^.while_body);
+  context^.indentation := context^.indentation - 1u;
+  indent(context);
+  WriteString(context^.output, "END")
+end;
+
+proc transpile_assignment_statement(context: ^TranspilerContext, statement: ^AstStatement);
+begin
+  transpile_expression(context, statement^.assignee);
+  WriteString(context^.output, " := ");
+  transpile_expression(context, statement^.assignment)
+end;
+
+proc transpile_return_statement(context: ^TranspilerContext, statement: ^AstStatement);
+begin
+  WriteString(context^.output, "RETURN ");
+
+  transpile_expression(context, statement^.returned)
+end;
+
+proc transpile_compound_statement(context: ^TranspilerContext, statement: AstCompoundStatement);
+var
+  current_statement: ^^AstStatement;
+  index: Word;
+begin
+  index := 0;
+  current_statement := statement.statements;
+
+  while index < statement.count do
+    transpile_statement(context, current_statement^);
+
+    current_statement := current_statement + 1;
+    index := index + 1u;
+
+    if index <> statement.count then
+      WriteChar(context^.output, ';')
+    end;
+    WriteLine(context^.output)
+  end
+end;
+
+proc transpile_statement(context: ^TranspilerContext, statement: ^AstStatement);
+begin
+  indent(context);
+
+  if statement^.kind = astStatementKindIf then
+    transpile_if_statement(context, statement)
+  end;
+  if statement^.kind = astStatementKindWhile then
+    transpile_while_statement(context, statement)
+  end;
+  if statement^.kind = astStatementKindReturn then
+    transpile_return_statement(context, statement)
+  end;
+  if statement^.kind = astStatementKindAssignment then
+    transpile_assignment_statement(context, statement)
+  end;
+  if statement^.kind = astStatementKindCall then
+    transpile_expression(context, statement^.call)
+  end
+end;
+
+proc transpile_statement_part(context: ^TranspilerContext, compound: AstCompoundStatement);
+begin
+  if compound.count > 0 then
+    WriteString(context^.output, "BEGIN");
+    WriteLine(context^.output);
+
+    context^.indentation := context^.indentation + 1u;
+    transpile_compound_statement(context, compound);
+    context^.indentation := context^.indentation - 1u;
+  end
+end;
+
+proc transpile_procedure_declaration(context: ^TranspilerContext, declaration: ^AstProcedureDeclaration);
+begin
+  transpile_procedure_heading(context, declaration);
+
+  transpile_constant_part(context, declaration^.constants, false);
+  transpile_variable_part(context, declaration^.variables, false);
+  transpile_statement_part(context, declaration^.statements);
+
+  WriteString(context^.output, "END ");
+  transpile_identifier(context^.output, declaration^.name);
+
+  write_semicolon(context^.output)
+end;
+
+proc transpile_procedure_part(context: ^TranspilerContext, declaration: ^^AstProcedureDeclaration);
+begin
+  while declaration^ <> nil do
+    transpile_procedure_declaration(context, declaration^);
+    WriteLine(context^.output);
+
+    declaration := declaration + 1
+  end
+end;
+
+proc transpile_module_name(context: ^TranspilerContext);
+var
+  counter: Word;
+  last_slash: Word;
+begin
+  counter := 1u;
+  last_slash := 0u;
+
+  while context^.input_name[counter] <> '.' & context^.input_name[counter] <> '\0' do
+    if context^.input_name[counter] = '/' then
+      last_slash := counter
+    end;
+    counter := counter + 1u
+  end;
+
+  if last_slash = 0u then
+    counter := 1u
+  end;
+  if last_slash <> 0u then
+    counter := last_slash + 1u
+  end;
+  while context^.input_name[counter] <> '.' & context^.input_name[counter] <> '\0' do
+    WriteChar(context^.output, context^.input_name[counter]);
+    counter := counter + 1u
+  end
+end;
+
+proc transpile*(ast_module: ^AstModule, output: File, definition: File, input_name: String);
+var
+  context: TranspilerContext;
+begin
+  context.input_name := input_name;
+  context.output := output;
+  context.definition := definition;
+  context.indentation := 0u;
+
+  transpile_module(@context, ast_module)
+end;
+
+end.

source/cctype.elna

@@ -0,0 +1,14 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+proc isdigit*(c: Int ) -> Int; extern;
+proc isalnum*(c: Int) -> Int; extern;
+proc isalpha*(c: Int) -> Int; extern;
+proc isspace*(c: Int) -> Int; extern;
+
+proc tolower*(c: Int) -> Int; extern;
+proc toupper*(c: Int) -> Int; extern;
+
+end.

source/command_line_interface.elna

@@ -0,0 +1,93 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+
+(*
+  Command line handling.
+*)
+module;
+
+import cstdlib, cstring, common;
+
+type
+  CommandLine* = record
+    input: ^Char;
+    output: ^Char;
+    lex: Bool;
+    parse: Bool
+  end;
+
+proc parse_command_line*(argc: Int, argv: ^^Char) -> ^CommandLine;
+var
+  parameter: ^Char;
+  i: Int;
+  result: ^CommandLine;
+  parsed: Bool;
+begin
+  i := 1;
+  result := cast(malloc(#size(CommandLine)): ^CommandLine);
+  result^.lex := false;
+  result^.parse := false;
+  result^.input := nil;
+  result^.output := nil;
+
+  while i < argc & result <> nil do
+    parameter := (argv + i)^;
+    parsed := false;
+
+    if strcmp(parameter, "--lex\0".ptr) = 0 then
+      parsed := true;
+      result^.lex := true
+    end;
+    if strcmp(parameter, "--parse\0".ptr) = 0 then
+      parsed := true;
+      result^.parse := true
+    end;
+    if strcmp(parameter, "-o\0".ptr) = 0 then
+      i := i + 1;
+
+      if i = argc then
+        write_s("Fatal error: expecting a file name following -o.");
+        result := nil
+      end;
+      if i < argc then
+        parameter := (argv + i)^;
+        result^.output := parameter
+      end;
+      parsed := true
+    end;
+    if (parameter^ <> '-') & ~parsed then
+      parsed := true;
+
+      if result^.input <> nil then
+        write_s("Fatal error: only one source file can be compiled at once. First given \"");
+        write_z(result^.input);
+        write_s("\", then \"");
+        write_z(parameter);
+        write_s("\".\n");
+        result := nil
+      end;
+      if result <> nil then
+        result^.input := parameter
+      end
+    end;
+    if ~parsed then
+      write_s("Fatal error: unknown command line options: ");
+
+      write_z(parameter);
+      write_s(".\n");
+
+      result := nil
+    end;
+
+    i := i + 1
+  end;
+  if result <> nil & result^.input = nil then
+    write_s("Fatal error: no input files.\n");
+    result := nil
+  end;
+
+  return result
+end;
+
+end.

source/common.elna

@@ -0,0 +1,72 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+import cstring, cstdio;
+
+type
+  Identifier = [256]Char;
+  TextLocation* = record
+    line: Word;
+    column: Word
+  end;
+
+proc write*(fd: Int, buf: Pointer, Word: Int) -> Int; extern;
+
+proc write_s*(value: String);
+begin
+  (* fwrite(cast(value.ptr: Pointer), value.length, 1u, stdout) *)
+  write(1, cast(value.ptr: Pointer), cast(value.length: Int))
+end;
+
+proc write_z*(value: ^Char);
+begin
+  write(1, cast(value: Pointer), cast(strlen(value): Int))
+end;
+
+proc write_b*(value: Bool);
+begin
+  if value then
+    write_s("true")
+  else
+    write_s("false")
+  end
+end;
+
+proc write_c*(value: Char);
+begin
+  putchar(cast(value: Int));
+  fflush(nil)
+end;
+
+proc write_i*(value: Int);
+var
+  digit: Int;
+  n: Word;
+  buffer: [10]Char;
+begin
+  n := 10u;
+
+  if value = 0 then
+    write_c('0')
+  end;
+  while value <> 0 do
+    digit := value % 10;
+    value := value / 10;
+
+    buffer[n] := cast(cast('0': Int) + digit: Char);
+    n := n - 1u
+  end;
+  while n < 10u do
+    n := n + 1u;
+    write_c(buffer[n])
+  end
+end;
+
+proc write_u*(value: Word);
+begin
+  write_i(cast(value: Int))
+end;
+
+end.

source/cstdio.elna

@@ -0,0 +1,29 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+type
+  FILE* = record end;
+
+var
+  stdin*: ^FILE := extern;
+  stdout*: ^FILE := extern;
+  stderr*: ^FILE := extern;
+
+proc fopen*(pathname: ^Char, mode: ^Char) -> ^FILE; extern;
+proc fclose*(stream: ^FILE) -> Int; extern;
+proc fseek*(stream: ^FILE, off: Int, whence: Int) -> Int; extern;
+proc rewind*(stream: ^FILE); extern;
+proc ftell*(stream: ^FILE) -> Int; extern;
+proc fflush*(stream: ^FILE) -> Int; extern;
+
+proc fread*(ptr: Pointer, size: Word, nmemb: Word, stream: ^FILE) -> Word; extern;
+proc fwrite*(ptr: Pointer, size: Word, nitems: Word, stream: ^FILE) -> Word; extern;
+
+proc perror(s: ^Char); extern;
+
+proc puts(s: ^Char) -> Int; extern;
+proc putchar(c: Int) -> Int; extern;
+
+end.

source/cstdlib.elna

@@ -0,0 +1,15 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+proc malloc(size: Word) -> Pointer; extern;
+proc free(ptr: Pointer); extern;
+proc calloc(nmemb: Word, size: Word) -> Pointer; extern;
+proc realloc(ptr: Pointer, size: Word) -> Pointer; extern;
+
+proc atoi(str: ^Char) -> Int; extern;
+
+proc exit(code: Int) -> !; extern;
+
+end.

source/cstring.elna

@@ -0,0 +1,15 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+proc memset(ptr: Pointer, c: Int, n: Word) -> ^Char; extern;
+proc memcpy(dst: Pointer, src: Pointer, n: Word); extern;
+
+proc strcmp(s1: ^Char, s2: ^Char) -> Int; extern;
+proc strncmp(s1: ^Char, s2: ^Char, n: Word) -> Int; extern;
+proc strncpy(dst: ^Char, src: ^Char, dsize: Word) -> ^Char; extern;
+proc strcpy(dst: ^Char, src: ^Char) -> ^Char; extern;
+proc strlen(ptr: ^Char) -> Word; extern;
+
+end.

source/lexer.elna

@@ -0,0 +1,952 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+module;
+
+import cstdio, cstring, cctype, cstdlib, common;
+
+const
+  CHUNK_SIZE := 85536u;
+
+type
+  (*
+   * Classification table assigns each possible character to a group (class). All
+   * characters of the same group are handled equivalently.
+   *
+   * Classification:
+   *)
+  TransitionClass = (
+    invalid,
+    digit,
+    alpha,
+    space,
+    colon,
+    equals,
+    left_paren,
+    right_paren,
+    asterisk,
+    underscore,
+    single,
+    hex,
+    zero,
+    x,
+    eof,
+    dot,
+    minus,
+    single_quote,
+    double_quote,
+    greater,
+    less,
+    other
+  );
+  TransitionState = (
+    start,
+    colon,
+    identifier,
+    decimal,
+    greater,
+    minus,
+    left_paren,
+    less,
+    dot,
+    comment,
+    closing_comment,
+    character,
+    string,
+    leading_zero,
+    decimal_suffix,
+    finish
+  );
+  LexerToken = record
+    kind: LexerKind;
+    value: union
+      booleanKind: Bool;
+      identifierKind: Identifier;
+      integerKind: Int;
+      stringKind: String
+    end;
+    start_location: TextLocation;
+    end_location: TextLocation
+  end;
+  TransitionAction = proc(^Lexer, ^LexerToken);
+  Transition = record
+    action: TransitionAction;
+    next_state: TransitionState
+  end;
+  TransitionClasses = [22]Transition;
+
+  BufferPosition* = record
+    iterator: ^Char;
+    location: TextLocation
+  end;
+  Lexer* = record
+    input: ^FILE;
+    buffer: ^Char;
+    size: Word;
+    length: Word;
+    start: BufferPosition;
+    current: BufferPosition
+  end;
+  LexerKind* = (
+    unknown,
+    identifier,
+    _if,
+    _then,
+    _else,
+    _elsif,
+    _while,
+    _do,
+    _proc,
+    _begin,
+    _end,
+    _extern,
+    _const,
+    _var,
+    _case,
+    _of,
+    _type,
+    _record,
+    _union,
+    pipe,
+    to,
+    boolean,
+    null,
+    and,
+    _or,
+    _xor,
+    not,
+    _return,
+    _cast,
+    shift_left,
+    shift_right,
+    left_paren,
+    right_paren,
+    left_square,
+    right_square,
+    greater_equal,
+    less_equal,
+    greater_than,
+    less_than,
+    not_equal,
+    equal,
+    semicolon,
+    dot,
+    comma,
+    plus,
+    minus,
+    multiplication,
+    division,
+    remainder,
+    assignment,
+    colon,
+    hat,
+    at,
+    comment,
+    integer,
+    word,
+    character,
+    string,
+    _defer,
+    exclamation,
+    arrow,
+    trait,
+    _program,
+    _module,
+    _import
+  );
+
+var
+  classification: [128]TransitionClass;
+  transitions: [16]TransitionClasses;
+
+proc initialize_classification();
+var
+  i: Word;
+begin
+  classification[1] := TransitionClass.eof; (* NUL *)
+  classification[2] := TransitionClass.invalid; (* SOH *)
+  classification[3] := TransitionClass.invalid; (* STX *)
+  classification[4] := TransitionClass.invalid; (* ETX *)
+  classification[5] := TransitionClass.invalid; (* EOT *)
+  classification[6] := TransitionClass.invalid; (* EMQ *)
+  classification[7] := TransitionClass.invalid; (* ACK *)
+  classification[8] := TransitionClass.invalid; (* BEL *)
+  classification[9] := TransitionClass.invalid; (* BS *)
+  classification[10] := TransitionClass.space; (* HT *)
+  classification[11] := TransitionClass.space; (* LF *)
+  classification[12] := TransitionClass.invalid; (* VT *)
+  classification[13] := TransitionClass.invalid; (* FF *)
+  classification[14] := TransitionClass.space; (* CR *)
+  classification[15] := TransitionClass.invalid; (* SO *)
+  classification[16] := TransitionClass.invalid; (* SI *)
+  classification[17] := TransitionClass.invalid; (* DLE *)
+  classification[18] := TransitionClass.invalid; (* DC1 *)
+  classification[19] := TransitionClass.invalid; (* DC2 *)
+  classification[20] := TransitionClass.invalid; (* DC3 *)
+  classification[21] := TransitionClass.invalid; (* DC4 *)
+  classification[22] := TransitionClass.invalid; (* NAK *)
+  classification[23] := TransitionClass.invalid; (* SYN *)
+  classification[24] := TransitionClass.invalid; (* ETB *)
+  classification[25] := TransitionClass.invalid; (* CAN *)
+  classification[26] := TransitionClass.invalid; (* EM *)
+  classification[27] := TransitionClass.invalid; (* SUB *)
+  classification[28] := TransitionClass.invalid; (* ESC *)
+  classification[29] := TransitionClass.invalid; (* FS *)
+  classification[30] := TransitionClass.invalid; (* GS *)
+  classification[31] := TransitionClass.invalid; (* RS *)
+  classification[32] := TransitionClass.invalid; (* US *)
+  classification[33] := TransitionClass.space; (* Space *)
+  classification[34] := TransitionClass.single; (* ! *)
+  classification[35] := TransitionClass.double_quote; (* " *)
+  classification[36] := TransitionClass.other; (* # *)
+  classification[37] := TransitionClass.other; (* $ *)
+  classification[38] := TransitionClass.single; (* % *)
+  classification[39] := TransitionClass.single; (* & *)
+  classification[40] := TransitionClass.single_quote; (* ' *)
+  classification[41] := TransitionClass.left_paren; (* ( *)
+  classification[42] := TransitionClass.right_paren; (* ) *)
+  classification[43] := TransitionClass.asterisk; (* * *)
+  classification[44] := TransitionClass.single; (* + *)
+  classification[45] := TransitionClass.single; (* , *)
+  classification[46] := TransitionClass.minus; (* - *)
+  classification[47] := TransitionClass.dot; (* . *)
+  classification[48] := TransitionClass.single; (* / *)
+  classification[49] := TransitionClass.zero; (* 0 *)
+  classification[50] := TransitionClass.digit; (* 1 *)
+  classification[51] := TransitionClass.digit; (* 2 *)
+  classification[52] := TransitionClass.digit; (* 3 *)
+  classification[53] := TransitionClass.digit; (* 4 *)
+  classification[54] := TransitionClass.digit; (* 5 *)
+  classification[55] := TransitionClass.digit; (* 6 *)
+  classification[56] := TransitionClass.digit; (* 7 *)
+  classification[57] := TransitionClass.digit; (* 8 *)
+  classification[58] := TransitionClass.digit; (* 9 *)
+  classification[59] := TransitionClass.colon; (* : *)
+  classification[60] := TransitionClass.single; (* ; *)
+  classification[61] := TransitionClass.less; (* < *)
+  classification[62] := TransitionClass.equals; (* = *)
+  classification[63] := TransitionClass.greater; (* > *)
+  classification[64] := TransitionClass.other; (* ? *)
+  classification[65] := TransitionClass.single; (* @ *)
+  classification[66] := TransitionClass.alpha; (* A *)
+  classification[67] := TransitionClass.alpha; (* B *)
+  classification[68] := TransitionClass.alpha; (* C *)
+  classification[69] := TransitionClass.alpha; (* D *)
+  classification[70] := TransitionClass.alpha; (* E *)
+  classification[71] := TransitionClass.alpha; (* F *)
+  classification[72] := TransitionClass.alpha; (* G *)
+  classification[73] := TransitionClass.alpha; (* H *)
+  classification[74] := TransitionClass.alpha; (* I *)
+  classification[75] := TransitionClass.alpha; (* J *)
+  classification[76] := TransitionClass.alpha; (* K *)
+  classification[77] := TransitionClass.alpha; (* L *)
+  classification[78] := TransitionClass.alpha; (* M *)
+  classification[79] := TransitionClass.alpha; (* N *)
+  classification[80] := TransitionClass.alpha; (* O *)
+  classification[81] := TransitionClass.alpha; (* P *)
+  classification[82] := TransitionClass.alpha; (* Q *)
+  classification[83] := TransitionClass.alpha; (* R *)
+  classification[84] := TransitionClass.alpha; (* S *)
+  classification[85] := TransitionClass.alpha; (* T *)
+  classification[86] := TransitionClass.alpha; (* U *)
+  classification[87] := TransitionClass.alpha; (* V *)
+  classification[88] := TransitionClass.alpha; (* W *)
+  classification[89] := TransitionClass.alpha; (* X *)
+  classification[90] := TransitionClass.alpha; (* Y *)
+  classification[91] := TransitionClass.alpha; (* Z *)
+  classification[92] := TransitionClass.single; (* [ *)
+  classification[93] := TransitionClass.other; (* \ *)
+  classification[94] := TransitionClass.single; (* ] *)
+  classification[95] := TransitionClass.single; (* ^ *)
+  classification[96] := TransitionClass.underscore; (* _ *)
+  classification[97] := TransitionClass.other; (* ` *)
+  classification[98] := TransitionClass.hex; (* a *)
+  classification[99] := TransitionClass.hex; (* b *)
+  classification[100] := TransitionClass.hex; (* c *)
+  classification[101] := TransitionClass.hex; (* d *)
+  classification[102] := TransitionClass.hex; (* e *)
+  classification[103] := TransitionClass.hex; (* f *)
+  classification[104] := TransitionClass.alpha; (* g *)
+  classification[105] := TransitionClass.alpha; (* h *)
+  classification[106] := TransitionClass.alpha; (* i *)
+  classification[107] := TransitionClass.alpha; (* j *)
+  classification[108] := TransitionClass.alpha; (* k *)
+  classification[109] := TransitionClass.alpha; (* l *)
+  classification[110] := TransitionClass.alpha; (* m *)
+  classification[111] := TransitionClass.alpha; (* n *)
+  classification[112] := TransitionClass.alpha; (* o *)
+  classification[113] := TransitionClass.alpha; (* p *)
+  classification[114] := TransitionClass.alpha; (* q *)
+  classification[115] := TransitionClass.alpha; (* r *)
+  classification[116] := TransitionClass.alpha; (* s *)
+  classification[117] := TransitionClass.alpha; (* t *)
+  classification[118] := TransitionClass.alpha; (* u *)
+  classification[119] := TransitionClass.alpha; (* v *)
+  classification[120] := TransitionClass.alpha; (* w *)
+  classification[121] := TransitionClass.x; (* x *)
+  classification[122] := TransitionClass.alpha; (* y *)
+  classification[123] := TransitionClass.alpha; (* z *)
+  classification[124] := TransitionClass.other; (* { *)
+  classification[125] := TransitionClass.single; (* | *)
+  classification[126] := TransitionClass.other; (* } *)
+  classification[127] := TransitionClass.single; (* ~ *)
+  classification[128] := TransitionClass.invalid; (* DEL *)
+
+  i := 129u;
+  while i <= 256u do
+    classification[i] := TransitionClass.other;
+    i := i + 1u
+  end
+end;
+
+proc compare_keyword(keyword: String, token_start: BufferPosition, token_end: ^Char) -> Bool;
+var
+  result: Bool;
+  index: Word;
+  continue: Bool;
+begin
+  index := 0u;
+  result := true;
+  continue := (index < keyword.length) & (token_start.iterator <> token_end);
+
+  while continue & result do
+    result := keyword[index] = token_start.iterator^
+      or cast(tolower(cast(keyword[index]: Int)): Char) = token_start.iterator^;
+    token_start.iterator := token_start.iterator + 1;
+    index := index + 1u;
+    continue := (index < keyword.length) & (token_start.iterator <> token_end)
+  end;
+  result := result & index = keyword.length;
+
+  return result & (token_start.iterator = token_end)
+end;
+
+(* Reached the end of file. *)
+proc transition_action_eof(lexer: ^Lexer, token: ^LexerToken);
+begin
+  token^.kind := LexerKind.unknown
+end;
+
+proc increment(position: ^BufferPosition);
+begin
+  position^.iterator := position^.iterator + 1
+end;
+
+(* Add the character to the token currently read and advance to the next character. *)
+proc transition_action_accumulate(lexer: ^Lexer, token: ^LexerToken);
+begin
+  increment(@lexer^.current)
+end;
+
+(* The current character is not a part of the token. Finish the token already
+ * read. Don't advance to the next character. *)
+proc transition_action_finalize(lexer: ^Lexer, token: ^LexerToken);
+begin
+  if lexer^.start.iterator^ = ':' then
+    token^.kind := LexerKind.colon
+  end;
+  if lexer^.start.iterator^ = '>' then
+    token^.kind := LexerKind.greater_than
+  end;
+  if lexer^.start.iterator^ = '<' then
+    token^.kind := LexerKind.less_than
+  end;
+  if lexer^.start.iterator^ = '(' then
+    token^.kind := LexerKind.left_paren
+  end;
+  if lexer^.start.iterator^ = '-' then
+    token^.kind := LexerKind.minus
+  end;
+  if lexer^.start.iterator^ = '.' then
+    token^.kind := LexerKind.dot
+  end
+end;
+
+(* An action for tokens containing multiple characters. *)
+proc transition_action_composite(lexer: ^Lexer, token: ^LexerToken);
+begin
+  if lexer^.start.iterator^ = '<' then
+    if lexer^.current.iterator^ = '>' then
+      token^.kind := LexerKind.not_equal
+    end;
+    if lexer^.current.iterator^ = '=' then
+      token^.kind := LexerKind.less_equal
+    end
+  end;
+  if (lexer^.start.iterator^ = '>') & (lexer^.current.iterator^ = '=') then
+    token^.kind := LexerKind.greater_equal
+  end;
+  if (lexer^.start.iterator^ = ':') & (lexer^.current.iterator^ = '=') then
+    token^.kind := LexerKind.assignment
+  end;
+  if (lexer^.start.iterator^ = '-') & (lexer^.current.iterator^ = '>') then
+    token^.kind := LexerKind.arrow
+  end;
+  increment(@lexer^.current)
+end;
+
+(* Skip a space. *)
+proc transition_action_skip(lexer: ^Lexer, token: ^LexerToken);
+begin
+  increment(@lexer^.start);
+
+  if lexer^.start.iterator^ = '\n' then
+    lexer^.start.location.line := lexer^.start.location.line + 1u;
+    lexer^.start.location.column := 1u
+  end;
+  lexer^.current := lexer^.start
+end;
+
+(* Delimited string action. *)
+proc transition_action_delimited(lexer: ^Lexer, token: ^LexerToken);
+var
+  text_length: Word;
+begin
+  if lexer^.start.iterator^ = '(' then
+    token^.kind := LexerKind.comment
+  end;
+  if lexer^.start.iterator^ = '"' then
+    text_length := cast(lexer^.current.iterator - lexer^.start.iterator + 1: Word);
+
+    token^.value.stringKind := String(cast(malloc(text_length): ^Char), text_length);
+    memcpy(cast(token^.value.stringKind.ptr: Pointer), cast(lexer^.start.iterator: Pointer), text_length);
+
+    token^.kind := LexerKind.character
+  end;
+  if lexer^.start.iterator^ = '\'' then
+    text_length := cast(lexer^.current.iterator - lexer^.start.iterator + 1: Word);
+
+    token^.value.stringKind := String(cast(malloc(text_length): ^Char), text_length);
+    memcpy(cast(token^.value.stringKind.ptr: Pointer), cast(lexer^.start.iterator: Pointer), text_length);
+
+    token^.kind := LexerKind.string
+  end;
+  increment(@lexer^.current)
+end;
+
+(* Finalize keyword or identifier. *)
+proc transition_action_key_id(lexer: ^Lexer, token: ^LexerToken);
+begin
+  token^.kind := LexerKind.identifier;
+
+  token^.value.identifierKind[1] := cast(lexer^.current.iterator - lexer^.start.iterator: Char);
+  memcpy(cast(@token^.value.identifierKind[2]: Pointer), cast(lexer^.start.iterator: Pointer), cast(token^.value.identifierKind[1]: Word));
+
+  if compare_keyword("program", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._program
+  end;
+  if compare_keyword("import", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._import
+  end;
+  if compare_keyword("const", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._const
+  end;
+  if compare_keyword("var", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._var
+  end;
+  if compare_keyword("if", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._if
+  end;
+  if compare_keyword("then", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._then
+  end;
+  if compare_keyword("elsif", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._elsif
+  end;
+  if compare_keyword("else", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._else
+  end;
+  if compare_keyword("while", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._while
+  end;
+  if compare_keyword("do", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._do
+  end;
+  if compare_keyword("proc", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._proc
+  end;
+  if compare_keyword("begin", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._begin
+  end;
+  if compare_keyword("end", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._end
+  end;
+  if compare_keyword("type", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._type
+  end;
+  if compare_keyword("record", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._record
+  end;
+  if compare_keyword("union", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._union
+  end;
+  if compare_keyword("NIL", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind.null
+  end;
+  if compare_keyword("or", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._or
+  end;
+  if compare_keyword("return", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._return
+  end;
+  if compare_keyword("defer", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._defer
+  end;
+  if compare_keyword("TO", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind.to
+  end;
+  if compare_keyword("CASE", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._case
+  end;
+  if compare_keyword("OF", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._of
+  end;
+  if compare_keyword("module", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._module
+  end;
+  if compare_keyword("xor", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind._xor
+  end;
+  if compare_keyword("TRUE", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind.boolean;
+    token^.value.booleanKind := true
+  end;
+  if compare_keyword("FALSE", lexer^.start, lexer^.current.iterator) then
+    token^.kind := LexerKind.boolean;
+    token^.value.booleanKind := false
+  end
+end;
+
+(* Action for tokens containing only one character. The character cannot be
+ * followed by other characters forming a composite token. *)
+proc transition_action_single(lexer: ^Lexer, token: ^LexerToken);
+begin
+  if lexer^.current.iterator^ = '&' then
+    token^.kind := LexerKind.and
+  end;
+  if lexer^.current.iterator^ = ';' then
+    token^.kind := LexerKind.semicolon
+  end;
+  if lexer^.current.iterator^ = ',' then
+    token^.kind := LexerKind.comma
+  end;
+  if lexer^.current.iterator^ = '~' then
+    token^.kind := LexerKind.not
+  end;
+  if lexer^.current.iterator^ = ')' then
+    token^.kind := LexerKind.right_paren
+  end;
+  if lexer^.current.iterator^ = '[' then
+    token^.kind := LexerKind.left_square
+  end;
+  if lexer^.current.iterator^ = ']' then
+    token^.kind := LexerKind.right_square
+  end;
+  if lexer^.current.iterator^ = '^' then
+    token^.kind := LexerKind.hat
+  end;
+  if lexer^.current.iterator^ = '=' then
+    token^.kind := LexerKind.equal
+  end;
+  if lexer^.current.iterator^ = '+' then
+    token^.kind := LexerKind.plus
+  end;
+  if lexer^.current.iterator^ = '*' then
+    token^.kind := LexerKind.multiplication
+  end;
+  if lexer^.current.iterator^ = '/' then
+    token^.kind := LexerKind.division
+  end;
+  if lexer^.current.iterator^ = '%' then
+    token^.kind := LexerKind.remainder
+  end;
+  if lexer^.current.iterator^ = '@' then
+    token^.kind := LexerKind.at
+  end;
+  if lexer^.current.iterator^ = '|' then
+    token^.kind := LexerKind.pipe
+  end;
+  increment(@lexer^.current)
+end;
+
+(* Handle an integer literal. *)
+proc transition_action_integer(lexer: ^Lexer, token: ^LexerToken);
+var
+  buffer: String;
+  integer_length: Word;
+  found: Bool;
+begin
+  token^.kind := LexerKind.integer;
+
+  integer_length := cast(lexer^.current.iterator - lexer^.start.iterator: Word);
+  memset(cast(token^.value.identifierKind.ptr: Pointer), 0, #size(Identifier));
+  memcpy(cast(@token^.value.identifierKind[1]: Pointer), cast(lexer^.start.iterator: Pointer), integer_length);
+
+  token^.value.identifierKind[cast(token^.value.identifierKind[1]: Int) + 2] := '\0';
+  token^.value.integerKind := atoi(@token^.value.identifierKind[2])
+end;
+
+proc set_default_transition(current_state: TransitionState, default_action: TransitionAction, next_state: TransitionState) -> Int;
+var
+  default_transition: Transition;
+  state_index: Int;
+begin
+  default_transition.action := default_action;
+  default_transition.next_state := next_state;
+  state_index := cast(current_state: Int) + 1;
+
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.space: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.colon: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.left_paren: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.right_paren: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.single: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.x: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.dot: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.minus: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.single_quote: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.double_quote: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.less: Int) + 1] := default_transition;
+  transitions[state_index][cast(TransitionClass.other: Int) + 1] := default_transition;
+
+  return state_index
+end;
+
+(*
+ * The transition table describes transitions from one state to another, given
+ * a symbol (character class).
+ *
+ * The table has m rows and n columns, where m is the amount of states and n is
+ * the amount of classes. So given the current state and a classified character
+ * the table can be used to look up the next state.
+ *
+ * Each cell is a word long.
+ * - The least significant byte of the word is a row number (beginning with 0).
+ *   It specifies the target state. "ff" means that this is an end state and no
+ *   transition is possible.
+ * - The next byte is the action that should be performed when transitioning.
+ *   For the meaning of actions see labels in the lex_next function, which
+ *   handles each action.
+ *)
+proc initialize_transitions();
+var
+  state_index: Int;
+begin
+  (* Start state. *)
+  state_index := cast(TransitionState.start: Int) + 1;
+
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].next_state := TransitionState.decimal;
+
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.space: Int) + 1].action := transition_action_skip;
+  transitions[state_index][cast(TransitionClass.space: Int) + 1].next_state := TransitionState.start;
+
+  transitions[state_index][cast(TransitionClass.colon: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.colon: Int) + 1].next_state := TransitionState.colon;
+
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].action := transition_action_single;
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.left_paren: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.left_paren: Int) + 1].next_state := TransitionState.left_paren;
+
+  transitions[state_index][cast(TransitionClass.right_paren: Int) + 1].action := transition_action_single;
+  transitions[state_index][cast(TransitionClass.right_paren: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].action := transition_action_single;
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.single: Int) + 1].action := transition_action_single;
+  transitions[state_index][cast(TransitionClass.single: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].next_state := TransitionState.leading_zero;
+
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].action := transition_action_eof;
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.dot: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.dot: Int) + 1].next_state := TransitionState.dot;
+
+  transitions[state_index][cast(TransitionClass.minus: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.minus: Int) + 1].next_state := TransitionState.minus;
+
+  transitions[state_index][cast(TransitionClass.single_quote: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.single_quote: Int) + 1].next_state := TransitionState.character;
+
+  transitions[state_index][cast(TransitionClass.double_quote: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.double_quote: Int) + 1].next_state := TransitionState.string;
+
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1].next_state := TransitionState.greater;
+
+  transitions[state_index][cast(TransitionClass.less: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.less: Int) + 1].next_state := TransitionState.less;
+
+  transitions[state_index][cast(TransitionClass.other: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.other: Int) + 1].next_state := TransitionState.finish;
+
+  (* Colon state. *)
+  state_index := set_default_transition(TransitionState.colon, transition_action_finalize, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].action := transition_action_composite;
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].next_state := TransitionState.finish;
+
+  (* Identifier state. *)
+  state_index := set_default_transition(TransitionState.identifier, transition_action_key_id, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].next_state := TransitionState.identifier;
+
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].next_state := TransitionState.identifier;
+
+  (* Decimal state. *)
+  state_index := set_default_transition(TransitionState.decimal, transition_action_integer, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].next_state := TransitionState.decimal;
+
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].next_state := TransitionState.decimal_suffix;
+
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].next_state := TransitionState.decimal_suffix;
+
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].next_state := TransitionState.decimal;
+
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].next_state := TransitionState.decimal_suffix;
+
+  (* Greater state. *)
+  state_index := set_default_transition(TransitionState.greater, transition_action_finalize, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].action := transition_action_composite;
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].next_state := TransitionState.finish;
+
+  (* Minus state. *)
+  state_index := set_default_transition(TransitionState.minus, transition_action_finalize, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1].action := transition_action_composite;
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1].next_state := TransitionState.finish;
+
+  (* Left paren state. *)
+  state_index := set_default_transition(TransitionState.left_paren, transition_action_finalize, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].next_state := TransitionState.comment;
+
+  (* Less state. *)
+  state_index := set_default_transition(TransitionState.less, transition_action_finalize, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].action := transition_action_composite;
+  transitions[state_index][cast(TransitionClass.equals: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1].action := transition_action_composite;
+  transitions[state_index][cast(TransitionClass.greater: Int) + 1].next_state := TransitionState.finish;
+
+  (* Hexadecimal after 0x. *)
+  state_index := set_default_transition(TransitionState.dot, transition_action_finalize, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.dot: Int) + 1].action := transition_action_composite;
+  transitions[state_index][cast(TransitionClass.dot: Int) + 1].next_state := TransitionState.finish;
+
+  (* Comment. *)
+  state_index := set_default_transition(TransitionState.comment, transition_action_accumulate, TransitionState.comment);
+
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].next_state := TransitionState.closing_comment;
+
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].next_state := TransitionState.finish;
+
+  (* Closing comment. *)
+  state_index := set_default_transition(TransitionState.closing_comment, transition_action_accumulate, TransitionState.comment);
+
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.right_paren: Int) + 1].action := transition_action_delimited;
+  transitions[state_index][cast(TransitionClass.right_paren: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].action := transition_action_accumulate;
+  transitions[state_index][cast(TransitionClass.asterisk: Int) + 1].next_state := TransitionState.closing_comment;
+
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].next_state := TransitionState.finish;
+
+  (* Character. *)
+  state_index := set_default_transition(TransitionState.character, transition_action_accumulate, TransitionState.character);
+
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.single_quote: Int) + 1].action := transition_action_delimited;
+  transitions[state_index][cast(TransitionClass.single_quote: Int) + 1].next_state := TransitionState.finish;
+
+  (* String. *)
+  state_index := set_default_transition(TransitionState.string, transition_action_accumulate, TransitionState.string);
+
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.invalid: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.eof: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.double_quote: Int) + 1].action := transition_action_delimited;
+  transitions[state_index][cast(TransitionClass.double_quote: Int) + 1].next_state := TransitionState.finish;
+
+  (* Leading zero. *)
+  state_index := set_default_transition(TransitionState.leading_zero, transition_action_integer, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.underscore: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].next_state := TransitionState.finish;
+
+  (* Digit with a character suffix. *)
+  state_index := set_default_transition(TransitionState.decimal_suffix, transition_action_integer, TransitionState.finish);
+
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.alpha: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.digit: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.hex: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.zero: Int) + 1].next_state := TransitionState.finish;
+
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].action := nil;
+  transitions[state_index][cast(TransitionClass.x: Int) + 1].next_state := TransitionState.finish
+end;
+
+proc lexer_make*(lexer: ^Lexer, input: ^FILE);
+begin
+  lexer^.input := input;
+  lexer^.length := 0u;
+
+  lexer^.buffer := cast(malloc(CHUNK_SIZE): ^Char);
+  memset(cast(lexer^.buffer: Pointer), 0, CHUNK_SIZE);
+  lexer^.size := CHUNK_SIZE
+end;
+
+(* Returns the last read token. *)
+proc lexer_current*(lexer: ^Lexer) -> LexerToken;
+var
+  current_class: TransitionClass;
+  current_state: TransitionState;
+  current_transition: Transition;
+  result: LexerToken;
+  index1: Word;
+  index2: Word;
+begin
+  lexer^.current := lexer^.start;
+  current_state := TransitionState.start;
+
+  while current_state <> TransitionState.finish do
+    index1 := cast(lexer^.current.iterator^: Word) + 1u;
+    current_class := classification[index1];
+
+    index1 := cast(current_state: Word) + 1u;
+    index2 := cast(current_class: Word) + 1u;
+
+    current_transition := transitions[index1][index2];
+    if current_transition.action <> nil then
+      current_transition.action(lexer, @result)
+    end;
+    current_state := current_transition.next_state
+  end;
+  result.start_location := lexer^.start.location;
+  result.end_location := lexer^.current.location;
+
+  return result
+end;
+
+(* Read and return the next token. *)
+proc lexer_lex*(lexer: ^Lexer) -> LexerToken;
+var
+  result: LexerToken;
+begin
+  if lexer^.length = 0u then
+    lexer^.length := fread(cast(lexer^.buffer: Pointer), CHUNK_SIZE, 1u, lexer^.input);
+    lexer^.current.location.column := 1u;
+    lexer^.current.location.line := 1u;
+    lexer^.current.iterator := lexer^.buffer
+  end;
+  lexer^.start := lexer^.current;
+
+  result := lexer_current(lexer);
+  return result
+end;
+
+proc lexer_destroy*(lexer: ^Lexer);
+begin
+  free(cast(lexer^.buffer: Pointer))
+end;
+
+proc lexer_initialize();
+begin
+  initialize_classification();
+  initialize_transitions()
+end;
+
+end.

source/main.elna

@@ -0,0 +1,841 @@
+(* This Source Code Form is subject to the terms of the Mozilla Public License,
+  v. 2.0. If a copy of the MPL was not distributed with this file, You can
+  obtain one at https://mozilla.org/MPL/2.0/. *)
+program;
+
+import cstdio, cctype, common, command_line_interface, lexer;
+
+type
+  SourceFile* = record
+    buffer: [1024]Char;
+    handle: ^FILE;
+    size: Word;
+    index: Word
+  end;
+  StringBuffer* = record
+    data: Pointer;
+    size: Word;
+    capacity: Word
+  end;
+  SourceCode = record
+    position: TextLocation;
+
+    input: Pointer;
+    empty: proc(Pointer) -> Bool;
+    advance: proc(Pointer);
+    head: proc(Pointer) -> Char
+  end;
+  Token* = record
+    kind: LexerKind;
+    value: union
+      int_value: Int;
+      string: String;
+      boolean_value: Bool;
+      char_value: Char
+    end
+  end;
+  Tokenizer* = record
+    length: Word;
+    data: ^Token
+  end;
+
+(*
+  Standard procedures.
+*)
+proc reallocarray(ptr: Pointer, n: Word, size: Word) -> Pointer;
+  return realloc(ptr, n * size)
+end;
+
+proc substring(string: String, start: Word, count: Word) -> String;
+  return String(string.ptr + start, count)
+end;
+
+proc open_substring(string: String, start: Word) -> String;
+  return substring(string, start, string.length - start)
+end;
+
+proc string_dup(origin: String) -> String;
+var
+  copy: ^Char;
+begin
+  copy := cast(malloc(origin.length): ^Char);
+  strncpy(copy, origin.ptr, origin.length);
+
+  return String(copy, origin.length)
+end;
+
+proc string_buffer_new() -> StringBuffer;
+var
+  result: StringBuffer;
+begin
+  result.capacity := 64u;
+  result.data := malloc(result.capacity);
+  result.size := 0u;
+
+  return result
+end;
+
+proc string_buffer_push(buffer: ^StringBuffer, char: Char);
+begin
+  if buffer^.size >= buffer^.capacity then
+    buffer^.capacity := buffer^.capacity + 1024u;
+    buffer^.data := realloc(buffer^.data, buffer^.capacity)
+  end;
+  cast(buffer^.data + buffer^.size: ^Char)^ := cast(char: Char);
+  buffer^.size := buffer^.size + 1u
+end;
+
+proc string_buffer_pop(buffer: ^StringBuffer, count: Word);
+begin
+  buffer^.size := buffer^.size - count
+end;
+
+proc string_buffer_clear(buffer: ^StringBuffer) -> String;
+var
+  result: String;
+begin
+  result := String(cast(buffer^.data: ^Char), buffer^.size);
+  buffer^.size := 0u;
+  return result
+end;
+
+(*
+  Source code stream procedures.
+*)
+
+proc read_source(filename: ^Char) -> ^SourceFile;
+var
+  result: ^SourceFile;
+  file_handle: ^FILE;
+begin
+  file_handle := fopen(filename, "rb\0".ptr);
+
+  if file_handle <> nil then
+    result := cast(malloc(#size(SourceFile)): ^SourceFile);
+    result^.handle := file_handle;
+    result^.size := 0u;
+    result^.index := 1u
+  end;
+  return result
+end;
+
+proc source_file_empty(source_input: Pointer) -> Bool;
+var
+  source_file: ^SourceFile;
+begin
+  source_file := cast(source_input: ^SourceFile);
+
+  if source_file^.index > source_file^.size then
+    source_file^.size := fread(cast(@source_file^.buffer: Pointer), 1u, 1024u, source_file^.handle);
+    source_file^.index := 1u
+  end;
+
+  return source_file^.size = 0u
+end;
+
+proc source_file_head(source_input: Pointer) -> Char;
+var
+  source_file: ^SourceFile;
+begin
+  source_file := cast(source_input: ^SourceFile);
+
+  return source_file^.buffer[source_file^.index]
+end;
+
+proc source_file_advance(source_input: Pointer);
+var
+  source_file: ^SourceFile;
+begin
+  source_file := cast(source_input: ^SourceFile);
+
+  source_file^.index := source_file^.index + 1u
+end;
+
+proc source_code_empty(source_code: ^SourceCode) -> Bool;
+  return source_code^.empty(source_code^.input)
+end;
+
+proc source_code_head(source_code: SourceCode) -> Char;
+  return source_code.head(source_code.input)
+end;
+
+proc source_code_advance(source_code: ^SourceCode);
+begin
+  source_code^.advance(source_code^.input);
+  source_code^.position.column := source_code^.position.column
+end;
+
+proc source_code_break(source_code: ^SourceCode);
+begin
+  source_code^.position.line := source_code^.position.line + 1u;
+  source_code^.position.column := 0u
+end;
+
+proc source_code_expect(source_code: ^SourceCode, expected: Char) -> Bool;
+  return ~source_code_empty(source_code) & source_code_head(source_code^) = expected
+end;
+
+(*
+  Token procedures.
+*)
+
+proc lexer_escape(escape: Char, result: ^Char) -> Bool;
+var
+  successful: Bool;
+begin
+  case escape of
+    'n':
+      result^ := '\n';
+      successful := true
+    | 'a':
+      result^ := '\a';
+      successful := true
+    | 'b':
+      result^ := '\b';
+      successful := true
+    | 't':
+      result^ := '\t';
+      successful := true
+    | 'f':
+      result^ := '\f';
+      successful := true
+    | 'r':
+      result^ := '\r';
+      successful := true
+    | 'v':
+      result^ := '\v';
+      successful := true
+    | '\\':
+      result^ := '\\';
+      successful := true
+    | '\'':
+      result^ := '\'';
+      successful := true
+    | '"':
+      result^ := '"';
+      successful := true
+    | '?':
+      result^ := '\?';
+      successful := true
+    | '0':
+      result^ := '\0';
+      successful := true
+    else
+      successful := false
+  end;
+  return successful
+end;
+
+(* Skip spaces. *)
+proc lexer_spaces(source_code: ^SourceCode);
+var
+  current: Char;
+begin
+  while ~source_code_empty(source_code) & isspace(cast(source_code_head(source_code^): Int)) <> 0 do
+    current := source_code_head(source_code^);
+
+    if current = '\n' then
+      source_code_break(source_code)
+    end;
+    source_code_advance(source_code)
+  end
+end;
+
+(* Checker whether the character is allowed in an identificator. *)
+proc lexer_is_ident(char: Char) -> Bool;
+  return isalnum(cast(char: Int)) <> 0 or char = '_'
+end;
+
+proc lexer_identifier(source_code: ^SourceCode, token_content: ^StringBuffer);
+var
+  content_length: Word;
+begin
+  while ~source_code_empty(source_code) & lexer_is_ident(source_code_head(source_code^)) do
+    string_buffer_push(token_content, source_code_head(source_code^));
+    source_code_advance(source_code)
+  end
+end;
+
+proc lexer_comment(source_code: ^SourceCode, token_content: ^StringBuffer) -> Bool;
+var
+  trailing: Word;
+begin
+  trailing := 0u;
+
+  while ~source_code_empty(source_code) & trailing < 2u do
+    if source_code_head(source_code^) = '*' then
+      string_buffer_push(token_content, '*');
+      trailing := 1u
+    elsif source_code_head(source_code^) = ')' & trailing = 1u then
+      string_buffer_pop(token_content, 1u);
+      trailing := 2u
+    else
+      string_buffer_push(token_content, source_code_head(source_code^));
+      trailing := 0u
+    end;
+    source_code_advance(source_code)
+  end;
+
+  return trailing = 2u
+end;
+
+proc lexer_character(source_code: ^SourceCode, token_content: ^Char) -> Bool;
+var
+  successful: Bool;
+begin
+  successful := ~source_code_empty(source_code);
+
+  if successful then
+    if source_code_head(source_code^) = '\\' then
+      source_code_advance(source_code);
+
+      successful := ~source_code_empty(source_code) & lexer_escape(source_code_head(source_code^), token_content)
+    else
+      token_content^ := source_code_head(source_code^);
+      successful := true
+    end
+  end;
+  if successful then
+    source_code_advance(source_code)
+  end;
+  return successful
+end;
+
+proc lexer_string(source_code: ^SourceCode, token_content: ^StringBuffer) -> Bool;
+var
+  token_end, constructed_string: ^Char;
+  token_length: Word;
+  is_valid: Bool := true;
+  next_char: Char;
+begin
+  while is_valid & ~source_code_empty(source_code) & source_code_head(source_code^) <> '"' do
+    is_valid := lexer_character(source_code, @next_char);
+
+    if is_valid then
+      string_buffer_push(token_content, next_char)
+    end
+  end;
+
+  if is_valid & source_code_expect(source_code, '"') then
+    source_code_advance(source_code)
+  else
+    is_valid := false
+  end;
+  return is_valid
+end;
+
+proc lexer_number(source_code: ^SourceCode, token_content: ^Int);
+begin
+  token_content^ := 0;
+
+  while ~source_code_empty(source_code) & isdigit(cast(source_code_head(source_code^): Int)) <> 0 do
+    token_content^ := token_content^ * 10 + (cast(source_code_head(source_code^): Int) - cast('0': Int));
+
+    source_code_advance(source_code)
+  end
+end;
+
+(* Categorize an identifier. *)
+proc lexer_categorize(token_content: String) -> Token;
+var
+  current_token: Token;
+begin
+  if token_content = "if" then
+    current_token.kind := LexerKind._if
+  elsif token_content = "then" then
+    current_token.kind := LexerKind._then
+  elsif token_content = "else" then
+    current_token.kind := LexerKind._else
+  elsif token_content = "elsif" then
+    current_token.kind := LexerKind._elsif
+  elsif token_content = "while" then
+    current_token.kind := LexerKind._while
+  elsif token_content = "do" then
+    current_token.kind := LexerKind._do
+  elsif token_content = "proc" then
+    current_token.kind := LexerKind._proc
+  elsif token_content = "begin" then
+    current_token.kind := LexerKind._begin
+  elsif token_content = "end" then
+    current_token.kind := LexerKind._end
+  elsif token_content = "extern" then
+    current_token.kind := LexerKind._extern
+  elsif token_content = "const" then
+    current_token.kind := LexerKind._const
+  elsif token_content = "var" then
+    current_token.kind := LexerKind._var
+  elsif token_content = "case" then
+    current_token.kind := LexerKind._case
+  elsif token_content = "of" then
+    current_token.kind := LexerKind._of
+  elsif token_content = "type" then
+    current_token.kind := LexerKind._type
+  elsif token_content = "record" then
+    current_token.kind := LexerKind._record
+  elsif token_content = "union" then
+    current_token.kind := LexerKind._union
+  elsif token_content = "true" then
+    current_token.kind := LexerKind.boolean;
+    current_token.value.boolean_value := true
+  elsif token_content = "false" then
+    current_token.kind := LexerKind.boolean;
+    current_token.value.boolean_value := false
+  elsif token_content = "nil" then
+    current_token.kind := LexerKind.null
+  elsif token_content = "or" then
+    current_token.kind := LexerKind._or
+  elsif token_content = "return" then
+    current_token.kind := LexerKind._return
+  elsif token_content = "cast" then
+    current_token.kind := LexerKind._cast
+  elsif token_content = "defer" then
+    current_token.kind := LexerKind._defer
+  elsif token_content = "program" then
+    current_token.kind := LexerKind._program
+  elsif token_content = "module" then
+    current_token.kind := LexerKind._module
+  elsif token_content = "import" then
+    current_token.kind := LexerKind._import
+  else
+    current_token.kind := LexerKind.identifier;
+    current_token.value.string := string_dup(token_content)
+  end;
+
+  return current_token
+end;
+
+proc lexer_add_token(lexer: ^Tokenizer, token: Token);
+var
+  new_length: Word;
+begin
+  new_length := lexer^.length + 1u;
+  lexer^.data := cast(reallocarray(cast(lexer^.data: Pointer), new_length, #size(Token)): ^Token);
+  (lexer^.data + lexer^.length)^ := token;
+  lexer^.length := new_length
+end;
+
+(* Read the next token from the input. *)
+proc lexer_next(source_code: SourceCode, token_buffer: ^StringBuffer) -> Token;
+var
+  current_token: Token;
+  first_char: Char;
+begin
+  current_token.kind := LexerKind.unknown;
+
+  first_char := source_code_head(source_code);
+
+  if isalpha(cast(first_char: Int)) <> 0 or first_char = '_' then
+    lexer_identifier(@source_code, token_buffer);
+    current_token := lexer_categorize(string_buffer_clear(token_buffer))
+  elsif first_char = '#' then
+    source_code_advance(@source_code);
+    lexer_identifier(@source_code, token_buffer);
+
+    current_token.kind := LexerKind.trait;
+    current_token.value.string := string_dup(string_buffer_clear(token_buffer))
+  elsif isdigit(cast(first_char: Int)) <> 0 then
+    lexer_number(@source_code, @current_token.value.int_value);
+
+    if source_code_expect(@source_code, 'u') then
+      current_token.kind := LexerKind.word;
+        source_code_advance(@source_code)
+    else
+      current_token.kind := LexerKind.integer
+    end
+  elsif first_char = '(' then
+    source_code_advance(@source_code);
+
+    if source_code_empty(@source_code) then
+      current_token.kind := LexerKind.left_paren
+    elsif source_code_head(source_code) = '*' then
+      source_code_advance(@source_code);
+
+      if lexer_comment(@source_code, token_buffer) then
+        current_token.value.string := string_dup(string_buffer_clear(token_buffer));
+        current_token.kind := LexerKind.comment
+      else
+        current_token.kind := LexerKind.unknown
+      end
+    else
+      current_token.kind := LexerKind.left_paren
+    end
+  elsif first_char = ')' then
+    current_token.kind := LexerKind.right_paren;
+    source_code_advance(@source_code)
+  elsif first_char = '\'' then
+    source_code_advance(@source_code);
+
+    if lexer_character(@source_code, @current_token.value.char_value) & source_code_expect(@source_code, '\'') then
+      current_token.kind := LexerKind.character;
+      source_code_advance(@source_code)
+    else
+      current_token.kind := LexerKind.unknown
+    end
+  elsif first_char = '"' then
+    source_code_advance(@source_code);
+
+    if lexer_string(@source_code, token_buffer) then
+      current_token.kind := LexerKind.string;
+      current_token.value.string := string_dup(string_buffer_clear(token_buffer))
+    else
+      current_token.kind := LexerKind.unknown
+    end
+  elsif first_char = '[' then
+    current_token.kind := LexerKind.left_square;
+    source_code_advance(@source_code)
+  elsif first_char = ']' then
+    current_token.kind := LexerKind.right_square;
+    source_code_advance(@source_code)
+  elsif first_char = '>' then
+    source_code_advance(@source_code);
+
+    if source_code_empty(@source_code) then
+      current_token.kind := LexerKind.greater_than
+    elsif source_code_head(source_code) = '=' then
+      current_token.kind := LexerKind.greater_equal;
+      source_code_advance(@source_code)
+    elsif source_code_head(source_code) = '>' then
+      current_token.kind := LexerKind.shift_right;
+      source_code_advance(@source_code)
+    else
+      current_token.kind := LexerKind.greater_than
+    end
+  elsif first_char = '<' then
+    source_code_advance(@source_code);
+
+    if source_code_empty(@source_code) then
+      current_token.kind := LexerKind.less_than
+    elsif source_code_head(source_code) = '=' then
+      current_token.kind := LexerKind.less_equal;
+      source_code_advance(@source_code)
+    elsif source_code_head(source_code) = '<' then
+      current_token.kind := LexerKind.shift_left;
+      source_code_advance(@source_code)
+    elsif source_code_head(source_code) = '>' then
+      current_token.kind := LexerKind.not_equal;
+      source_code_advance(@source_code)
+    else
+      current_token.kind := LexerKind.less_than
+    end
+  elsif first_char = '=' then
+    current_token.kind := LexerKind.equal;
+    source_code_advance(@source_code)
+  elsif first_char = ';' then
+    current_token.kind := LexerKind.semicolon;
+    source_code_advance(@source_code)
+  elsif first_char = '.' then
+    current_token.kind := LexerKind.dot;
+    source_code_advance(@source_code)
+  elsif first_char = ',' then
+    current_token.kind := LexerKind.comma;
+    source_code_advance(@source_code)
+  elsif first_char = '+' then
+    current_token.kind := LexerKind.plus;
+    source_code_advance(@source_code)
+  elsif first_char = '-' then
+    source_code_advance(@source_code);
+
+    if source_code_empty(@source_code) then
+      current_token.kind := LexerKind.minus
+    elsif source_code_head(source_code) = '>' then
+      current_token.kind := LexerKind.arrow;
+      source_code_advance(@source_code)
+    else
+      current_token.kind := LexerKind.minus
+    end
+  elsif first_char = '*' then
+    current_token.kind := LexerKind.multiplication;
+    source_code_advance(@source_code)
+  elsif first_char = '/' then
+    current_token.kind := LexerKind.division;
+    source_code_advance(@source_code)
+  elsif first_char = '%' then
+    current_token.kind := LexerKind.remainder;
+    source_code_advance(@source_code)
+  elsif first_char = ':' then
+    source_code_advance(@source_code);
+
+    if source_code_empty(@source_code) then
+      current_token.kind := LexerKind.colon
+    elsif source_code_head(source_code) = '=' then
+      current_token.kind := LexerKind.assignment;
+      source_code_advance(@source_code)
+    else
+      current_token.kind := LexerKind.colon
+    end
+  elsif first_char = '^' then
+    current_token.kind := LexerKind.hat;
+    source_code_advance(@source_code)
+  elsif first_char = '@' then
+    current_token.kind := LexerKind.at;
+    source_code_advance(@source_code)
+  elsif first_char = '!' then
+    current_token.kind := LexerKind.exclamation;
+    source_code_advance(@source_code)
+  elsif first_char = '&' then
+    current_token.kind := LexerKind.and;
+    source_code_advance(@source_code)
+  elsif first_char = '~' then
+    current_token.kind := LexerKind.not;
+    source_code_advance(@source_code)
+  elsif first_char = '|' then
+    current_token.kind := LexerKind.pipe;
+    source_code_advance(@source_code)
+  else
+    current_token.kind := LexerKind.unknown;
+    source_code_advance(@source_code)
+  end;
+
+  return current_token
+end;
+
+(* Split the source text into tokens. *)
+proc lexer_text(source_code: SourceCode) -> Tokenizer;
+var
+  current_token: Token;
+  token_buffer: StringBuffer;
+  lexer: Tokenizer;
+begin
+  lexer := Tokenizer(0u, nil);
+  token_buffer := string_buffer_new();
+
+  lexer_spaces(@source_code);
+
+  while ~source_code_empty(@source_code) do
+    current_token := lexer_next(source_code, @token_buffer);
+
+    if current_token.kind <> LexerKind.unknown then
+      lexer_add_token(@lexer, current_token);
+        lexer_spaces(@source_code)
+    else
+      write_s("Lexical analysis error on \"");
+      write_c(source_code_head(source_code));
+      write_s("\".\n")
+    end
+  end;
+
+  return lexer
+end;
+
+(*
+  Parser.
+*)
+
+proc parse(tokens: ^Token, tokens_size: Word);
+var
+  current_token: ^Token;
+  i: Word := 0u;
+begin
+  while i < tokens_size do
+    current_token := tokens + i;
+
+    case current_token^.kind of
+      LexerKind._if:
+        write_s("IF")
+      | LexerKind._then:
+        write_s("THEN")
+      | LexerKind._else:
+        write_s("ELSE")
+      | LexerKind._elsif:
+        write_s("ELSIF")
+      | LexerKind._while:
+        write_s("WHILE")
+      | LexerKind._do:
+        write_s("DO")
+      | LexerKind._proc:
+        write_s("PROC")
+      | LexerKind._begin:
+        write_s("BEGIN")
+      | LexerKind._end:
+        write_s("END")
+      | LexerKind._extern:
+        write_s("EXTERN")
+      | LexerKind._const:
+        write_s("CONST")
+      | LexerKind._var:
+        write_s("VAR")
+     | LexerKind._case:
+        write_s("CASE")
+      | LexerKind._of:
+        write_s("OF")
+      | LexerKind._type:
+        write_s("TYPE")
+      | LexerKind._record:
+        write_s("RECORD")
+      | LexerKind._union:
+        write_s("UNION")
+      | LexerKind.pipe:
+        write_s("|")
+      | LexerKind.to:
+        write_s("TO")
+      | LexerKind.boolean:
+        write_s("BOOLEAN<");
+        write_b(current_token^.value.boolean_value);
+        write_c('>')
+      | LexerKind.null:
+        write_s("NIL")
+      | LexerKind.and:
+        write_s("&")
+      | LexerKind._or:
+        write_s("OR")
+      | LexerKind.not:
+        write_s("~")
+      | LexerKind._return:
+        write_s("RETURN")
+      | LexerKind._cast:
+        write_s("CAST")
+      | LexerKind.shift_left:
+        write_s("<<")
+      | LexerKind.shift_right:
+        write_s(">>")
+      | LexerKind.identifier:
+        write_c('<');
+        write_s(current_token^.value.string);
+        write_c('>')
+      | LexerKind.trait:
+        write_c('#');
+        write_s(current_token^.value.string)
+      | LexerKind.left_paren:
+        write_s("(")
+      | LexerKind.right_paren:
+        write_s(")")
+      | LexerKind.left_square:
+        write_s("[")
+      | LexerKind.right_square:
+        write_s("]")
+      | LexerKind.greater_equal:
+        write_s(">=")
+      | LexerKind.less_equal:
+        write_s("<=")
+      | LexerKind.greater_than:
+        write_s(">")
+      | LexerKind.less_than:
+        write_s("<")
+      | LexerKind.equal:
+        write_s("=")
+      | LexerKind.not_equal:
+        write_s("<>")
+      | LexerKind.semicolon:
+        write_c(';')
+      | LexerKind.dot:
+        write_c('.')
+      | LexerKind.comma:
+        write_c(',')
+      | LexerKind.plus:
+        write_c('+')
+      | LexerKind.minus:
+        write_c('-')
+      | LexerKind.multiplication:
+        write_c('*')
+      | LexerKind.division:
+        write_c('/')
+      | LexerKind.remainder:
+        write_c('%')
+      | LexerKind.assignment:
+        write_s(":=")
+      | LexerKind.colon:
+        write_c(':')
+      | LexerKind.hat:
+        write_c('^')
+      | LexerKind.at:
+        write_c('@')
+      | LexerKind.comment:
+        write_s("(* COMMENT *)")
+      | LexerKind.integer:
+        write_c('<');
+        write_i(current_token^.value.int_value);
+        write_c('>')
+      | LexerKind.word:
+        write_c('<');
+        write_i(current_token^.value.int_value);
+        write_s("u>")
+      | LexerKind.character:
+        write_c('<');
+        write_i(cast(current_token^.value.char_value: Int));
+        write_s("c>")
+      | LexerKind.string:
+        write_s("\"...\"")
+      | LexerKind._defer:
+        write_s("DEFER")
+      | LexerKind.exclamation:
+        write_c('!')
+      | LexerKind.arrow:
+        write_s("->")
+      | LexerKind._program:
+        write_s("PROGRAM")
+      | LexerKind._module:
+      write_s("MODULE")
+      | LexerKind._import:
+      write_s("IMPORT")
+      else
+        write_s("UNKNOWN<");
+        write_i(cast(current_token^.kind: Int));
+        write_c('>')
+    end;
+    write_c(' ');
+
+    i := i + 1u
+  end;
+  write_c('\n')
+end;
+
+(*
+  Compilation entry.
+*)
+
+proc compile_in_stages(command_line: ^CommandLine, source_code: SourceCode) -> Int;
+var
+  return_code: Int := 0;
+  lexer: Tokenizer;
+begin
+  if command_line^.lex or command_line^.parse then
+    lexer := lexer_text(source_code)
+  end;
+  if command_line^.parse then
+    parse(lexer.data, lexer.length)
+  end;
+
+  return return_code
+end;
+
+proc process(argc: Int, argv: ^^Char) -> Int;
+var
+  tokens: ^Token;
+  tokens_size: Word;
+  source_code: SourceCode;
+  command_line: ^CommandLine;
+  return_code: Int := 0;
+  source_file: ^SourceFile;
+begin
+  command_line := parse_command_line(argc, argv);
+  if command_line = nil then
+    return_code := 2
+  end;
+
+  if return_code = 0 then
+    source_file := read_source(command_line^.input);
+
+    if source_file = nil then
+      perror(command_line^.input);
+      return_code := 3
+    end
+  end;
+
+  if return_code = 0 then
+    defer
+      fclose(source_file^.handle)
+    end;
+
+    source_code.position := TextLocation(1u, 1u);
+    source_code.input := cast(source_file: Pointer);
+    source_code.empty := source_file_empty;
+    source_code.head := source_file_head;
+    source_code.advance := source_file_advance;
+
+    return_code := compile_in_stages(command_line, source_code)
+  end;
+  return return_code
+end;
+
+  return process(count, parameters)
+end.