1 files changed, 1174 insertions, 0 deletions
diff --git a/source/Parser.elna b/source/Parser.elna
new file mode 100644
index 0000000..1225750
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+++ b/source/Parser.elna
@@ -0,0 +1,1174 @@
+(* 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 cstdlib, common, Lexer;
+
+type
+  Parser = record
+    lexer: ^Lexer
+  end;
+
+  AstLiteralKind* = (
+    integer,
+    string,
+    null,
+    boolean
+  );
+  AstLiteral* = record
+    kind: AstLiteralKind;
+    value: union
+      integer: Int;
+      string: String;
+      boolean: Bool
+    end
+  end;
+
+  AstUnaryOperator* = (
+    reference,
+    not,
+    minus
+  );
+  AstBinaryOperator* = (
+    sum,
+    subtraction,
+    multiplication,
+    division,
+    remainder,
+    equals,
+    not_equals,
+    less,
+    greater,
+    less_equal,
+    greater_equal,
+    disjunction,
+    conjunction,
+    exclusive_disjunction,
+    shift_left,
+    shift_right
+  );
+
+  AstExpressionKind* = (
+    literal,
+    identifier,
+    array_access,
+    dereference,
+    field_access,
+    unary,
+    binary,
+    call
+  );
+  AstExpression* = record 
+    kind: AstExpressionKind
+    value: union
+      literal: ^AstLiteral;
+      identifier: Identifier;
+      reference: ^AstExpression;
+      array_access: record
+        array: ^AstExpression;
+        index: ^AstExpression
+      end;
+      field_access: record
+        aggregate: ^AstExpression;
+        field: Identifier
+      end;
+      unary: record
+        operator: AstUnaryOperator;
+        operand: ^AstExpression
+      end;
+      binary: record
+        operator: AstBinaryOperator;
+        lhs: ^AstExpression;
+        rhs: ^AstExpression
+      end;
+      call: record
+        callable: ^AstExpression;
+        argument_count: Word;
+        arguments: ^^AstExpression
+      end
+    end
+  end;
+
+  ConditionalStatement = record
+    condition: ^AstExpression;
+    branch: AstCompoundStatement
+  end;
+
+  AstStatementKind* = (
+    if_statement,
+    while_statement,
+    assignment_statement,
+    return_statement,
+    call_statement
+  );
+  AstStatement* = record
+    kind: AstStatementKind
+    value: union
+      if_statement: ConditionalStatement;
+      while_statement: ConditionalStatement;
+      assignment_statement: record
+        assignee: ^AstExpression;
+        assignment: ^AstExpression
+      end;
+      return_statement: ^AstExpression;
+      call_statement: ^AstExpression
+    end
+  end;
+  AstCompoundStatement* = record
+    count: Word;
+    statements: ^^AstStatement
+  end;
+
+  AstImportStatement* = record
+    package: Identifier;
+    symbols: ^Identifier
+  end;
+
+  AstConstantDeclaration* = record
+    constant_name: Identifier;
+    constant_value: Int
+  end;
+
+  AstFieldDeclaration* = record
+    field_name: Identifier;
+    field_type: ^AstTypeExpression
+  end;
+
+  AstTypeExpressionKind* = (
+    named_expression,
+    record_expression,
+    enumeration_expression,
+    array_expression,
+    pointer_expression,
+    procedure_expression
+  );
+  AstTypeExpression* = record
+    kind: AstTypeExpressionKind;
+    value: union
+      name: Identifier;
+      cases: ^Identifier;
+      target: ^AstTypeExpression;
+      fields: ^AstFieldDeclaration;
+      array_expression: record
+        base: ^AstTypeExpression;
+        length: Word
+      end;
+      parameters: ^^AstTypeExpression
+    end
+  end;
+
+  AstTypedDeclaration* = record
+    identifier: Identifier;
+    type_expression: ^AstTypeExpression
+  end;
+
+  AstVariableDeclaration* = record
+    variable_name: Identifier;
+    variable_type: ^AstTypeExpression
+  end;
+
+  AstProcedureDeclaration* = record
+    name: Identifier;
+    parameter_count: Word;
+    parameters: ^AstTypedDeclaration;
+    return_type: ^AstTypeExpression;
+    constants: ^^AstConstantDeclaration;
+    variables: ^^AstVariableDeclaration;
+    statements: AstCompoundStatement
+  end;
+
+  AstModule* = record
+    main: Bool;
+    imports: ^^AstImportStatement;
+    constants: ^^AstConstantDeclaration;
+    types: ^^AstTypedDeclaration;
+    variables: ^^AstVariableDeclaration;
+    procedures: ^^AstProcedureDeclaration;
+    statements: AstCompoundStatement
+  end;
+
+(* Calls lexer_lex() but skips the comments. *)
+proc parser_lex(lexer: ^Lexer) -> LexerToken;
+var
+  result: LexerToken;
+begin
+  result := lexer_lex(lexer);
+
+  while result.kind = lexerKindComment do
+    result := lexer_lex(lexer)
+  end;
+
+  return result
+end;
+
+proc parse_type_fields(parser: ^Parser) -> ^AstFieldDeclaration;
+var
+  token: LexerToken;
+  field_declarations: ^AstFieldDeclaration;
+  field_count: Word;
+  current_field: ^AstFieldDeclaration;
+begin
+  field_declarations := malloc(#size(AstFieldDeclaration));
+  token := parser_lex(parser^.lexer);
+  field_count := 0;
+
+  while token.kind <> lexerKindEnd do
+    field_count := field_count + 2u;
+
+    field_declarations := realloc(field_declarations, #size(AstFieldDeclaration) * field_count);
+    field_count := field_count - 1u;
+    current_field := field_declarations + (field_count - 1u);
+
+    token := parser_lex(parser^.lexer);
+
+    current_field^.field_name := token.identifierKind;
+
+    token := parser_lex(parser^.lexer);
+    current_field^.field_type := parse_type_expression(parser);
+    token := parser_lex(parser^.lexer);
+
+    if token.kind = lexerKindSemicolon then
+      token := parser_lex(parser^.lexer)
+    end
+  end;
+  current_field := current_field + 1;
+  memset(current_field, 0, #size(AstFieldDeclaration));
+
+  return field_declarations
+end;
+
+proc parse_record_type(parser: ^Parser) -> ^AstTypeExpression;
+var
+  result: ^AstTypeExpression;
+begin
+  NEW(result);
+  result^.kind := AstTypeExpressionKind.record_expression;
+  result^.fields := parse_type_fields(parser);
+
+  return result
+end;
+
+proc parse_pointer_type(parser: ^Parser) -> ^AstTypeExpression;
+var
+  token: LexerToken;
+  result: ^AstTypeExpression;
+begin
+  NEW(result);
+  result^.kind := AstTypeExpressionKind.pointer_expression;
+
+  token := lexer_current(parser^.lexer);
+
+  if token.kind = lexerKindPointer then
+    token := parser_lex(parser^.lexer)
+  end;
+  token := lexer_current(parser^.lexer);
+  result^.target := parse_type_expression(parser);
+
+  return result
+end;
+
+proc parse_array_type(parser: ^Parser) -> ^AstTypeExpression;
+var
+  token: LexerToken;
+  buffer: [20]Char;
+  result: ^AstTypeExpression;
+begin
+  NEW(result);
+  result^.kind := AstTypeExpressionKind.array_expression;
+  result^.array_expression.length := 0u;
+
+  token := lexer_current(parser^.lexer);
+
+  if token.kind = lexerKindArray then
+    token := parser_lex(parser^.lexer)
+  end;
+  if token.kind <> lexerKindOf then
+    token := parser_lex(parser^.lexer);
+
+    result^.array_expression.length := token.integerKind;
+
+    token := parser_lex(parser^.lexer)
+  end;
+  token := parser_lex(parser^.lexer);
+  result^.array_expression.base := parse_type_expression(parser);
+
+  return result
+end;
+
+proc parse_enumeration_type(parser: ^Parser) -> ^AstTypeExpression;
+var
+  token: LexerToken;
+  result: ^AstTypeExpression;
+  current_case: ^Identifier;
+  case_count: Word;
+begin
+  NEW(result);
+  result^.kind := AstTypeExpressionKind.enumeration_expression;
+
+  case_count := 1u;
+  result^.cases := malloc(#size(Identifier) * 2);
+  token := parser_lex(parser^.lexer);
+  current_case := result^.cases;
+  current_case^ := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+
+  while token.kind = lexerKindComma do
+    token := parser_lex(parser^.lexer);
+
+    case_count := case_count + 2u;
+
+    result^.cases := realloc(result^.cases, #size(Identifier) * case_count);
+    case_count := case_count - 1u;
+    current_case := result^.cases + (case_count - 1u);
+    current_case^ := token.identifierKind;
+
+    token := parser_lex(parser^.lexer)
+  end;
+  current_case := current_case + 1;
+  memset(current_case, 0, #size(Identifier));
+
+  return result
+end;
+
+proc parse_named_type(parser: ^Parser) -> ^AstTypeExpression;
+var
+  token: LexerToken;
+  result: ^AstTypeExpression;
+begin
+  token := lexer_current(parser^.lexer);
+  NEW(result);
+
+  result^.kind := AstTypeExpressionKind.named_expression;
+  result^.name := token.identifierKind;
+
+  return result
+end;
+
+proc parse_procedure_type(parser: ^Parser) -> ^AstTypeExpression;
+var
+  token: LexerToken;
+  result: ^AstTypeExpression;
+  current_parameter: ^^AstTypeExpression;
+  parameter_count: Word;
+begin
+  parameter_count := 0u;
+  NEW(result);
+  result^.kind := AstTypeExpressionKind.procedure_expression;
+
+  result^.parameters := malloc(#size(^AstTypeExpression));
+
+  token := parser_lex(parser^.lexer);
+  token := parser_lex(parser^.lexer);
+
+  while token.kind <> lexerKindRightParen do
+    parameter_count := parameter_count + 2u;
+
+    result^.parameters := realloc(result^.parameters, #size(^AstTypeExpression) * parameter_count);
+    parameter_count := parameter_count - 1u;
+    current_parameter := result^.parameters + (parameter_count - 1u);
+
+    current_parameter^ := parse_type_expression(parser);
+
+    token := parser_lex(parser^.lexer);
+    if token.kind = lexerKindComma then
+      token := parser_lex(parser^.lexer)
+    end
+  end;
+  current_parameter := result^.parameters + parameter_count;
+  current_parameter^ := nil;
+
+  return result
+end;
+
+proc parse_type_expression(parser: ^Parser) -> ^AstTypeExpression;
+var
+  token: LexerToken;
+  result: ^AstTypeExpression;
+begin
+  result := nil;
+  token := lexer_current(parser^.lexer);
+
+  if token.kind = lexerKindRecord then
+    result := parse_record_type(parser)
+  end;
+  if token.kind = lexerKindLeftParen then
+    result := parse_enumeration_type(parser)
+  end;
+  if (token.kind = lexerKindArray) or (token.kind = lexerKindLeftSquare) then
+    result := parse_array_type(parser)
+  end;
+  if token.kind = lexerKindHat then
+    result := parse_pointer_type(parser)
+  end;
+  if token.kind = lexerKindProc then
+    result := parse_procedure_type(parser)
+  end;
+  if token.kind = lexerKindIdentifier then
+    result := parse_named_type(parser)
+  end;
+  return result
+end;
+
+proc parse_type_declaration(parser: ^Parser) -> ^AstTypedDeclaration;
+var
+  token: LexerToken;
+  result: ^AstTypedDeclaration;
+begin
+  token := lexer_current(parser^.lexer);
+
+  NEW(result);
+  result^.identifier := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+  token := parser_lex(parser^.lexer);
+
+  result^.type_expression := parse_type_expression(parser);
+  token := parser_lex(parser^.lexer);
+
+  return result
+end;
+
+proc parse_type_part(parser: ^Parser) -> ^^AstTypedDeclaration;
+var
+  token: LexerToken;
+  result: ^^AstTypedDeclaration;
+  current_declaration: ^^AstTypedDeclaration;
+  declaration_count: Word;
+begin
+  token := lexer_current(parser^.lexer);
+
+  result := malloc(#size(^AstTypedDeclaration));
+  current_declaration := result;
+  declaration_count := 0u;
+
+  if token.kind = lexerKindType then
+    token := parser_lex(parser^.lexer);
+
+    while token.kind = lexerKindIdentifier do
+      declaration_count := declaration_count + 1u;
+
+      result := realloc(result, #size(^AstTypedDeclaration) * (declaration_count + 1));
+      current_declaration := result + (declaration_count - 1u);
+
+      current_declaration^ := parse_type_declaration(parser);
+      token := parser_lex(parser^.lexer)
+    end
+  end;
+  if declaration_count <> 0u then
+    current_declaration := current_declaration + 1
+  end;
+  current_declaration^ := nil;
+
+  return result
+end;
+
+proc parse_variable_declaration(parser: ^Parser) -> ^AstVariableDeclaration;
+var
+  token: LexerToken;
+  result: ^AstVariableDeclaration;
+begin
+  NEW(result);
+
+  token := lexer_current(parser^.lexer);
+  result^.variable_name := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+
+  token := parser_lex(parser^.lexer);
+  result^.variable_type := parse_type_expression(parser);
+
+  token := parser_lex(parser^.lexer);
+  return result
+end;
+
+proc parse_variable_part(parser: ^Parser) -> ^^AstVariableDeclaration;
+var
+  token: LexerToken;
+  result: ^^AstVariableDeclaration;
+  current_declaration: ^^AstVariableDeclaration;
+  declaration_count: Word;
+begin
+  token := lexer_current(parser^.lexer);
+
+  result := malloc(#size(^AstVariableDeclaration));
+  current_declaration := result;
+  declaration_count := 0u;
+
+  if token.kind = lexerKindVar then
+    token := parser_lex(parser^.lexer);
+
+    while token.kind = lexerKindIdentifier do
+      declaration_count := declaration_count + 1u;
+
+      result := realloc(result, #size(^AstVariableDeclaration) * (declaration_count + 1));
+      current_declaration := result + (declaration_count - 1u);
+
+      current_declaration^ := parse_variable_declaration(parser);
+      token := parser_lex(parser^.lexer)
+    end
+  end;
+  if declaration_count <> 0 then
+    current_declaration := current_declaration + 1
+  end;
+  current_declaration^ := nil;
+
+  return result
+end;
+
+proc parse_constant_declaration(parser: ^Parser) -> ^AstConstantDeclaration;
+var
+  token: LexerToken;
+  result: ^AstConstantDeclaration;
+begin
+  NEW(result);
+
+  token := lexer_current(parser^.lexer);
+  result^.constant_name := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+
+  token := parser_lex(parser^.lexer);
+  result^.constant_value := token.integerKind;
+
+  token := parser_lex(parser^.lexer);
+
+  return result
+end;
+
+proc parse_constant_part(parser: ^Parser) -> ^^AstConstantDeclaration;
+var
+  token: LexerToken;
+  result: ^^AstConstantDeclaration;
+  current_declaration: ^^AstConstantDeclaration;
+  declaration_count: Word;
+begin
+  token := lexer_current(parser^.lexer);
+
+  result := malloc(#size(^AstConstantDeclaration));
+  current_declaration := result;
+  declaration_count := 0u;
+
+  if token.kind = lexerKindConst then
+    token := parser_lex(parser^.lexer);
+
+    while token.kind = lexerKindIdentifier do
+      declaration_count := declaration_count + 1u;
+
+      result := realloc(result, #size(^AstConstantDeclaration) * (declaration_count + 1u));
+      current_declaration := result + (declaration_count - 1u);
+
+      current_declaration^ := parse_constant_declaration(parser);
+      token := parser_lex(parser^.lexer)
+    end
+  end;
+  if declaration_count <> 0 then
+    current_declaration := current_declaration + 1
+  end;
+  current_declaration^ := nil;
+
+  return result
+end;
+
+proc parse_import_statement(parser: ^Parser) -> ^AstImportStatement;
+var
+  result: ^AstImportStatement;
+  token: LexerToken;
+  symbol_count: Word;
+  current_symbol: ^Identifier;
+begin
+  NEW(result);
+  symbol_count := 1u;
+
+  token := parser_lex(parser^.lexer);
+  result^.package := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+  result^.symbols := malloc(#size(Identifier) * 2);
+
+  current_symbol := result^.symbols;
+
+  token := parser_lex(parser^.lexer);
+  current_symbol^ := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+  while token.kind <> lexerKindSemicolon do
+    token := parser_lex(parser^.lexer);
+    symbol_count := symbol_count + 1u;
+
+    result^.symbols := realloc(result^.symbols, #size(Identifier) * (symbol_count + 1u));
+    current_symbol := result^.symbols + (symbol_count - 1u);
+
+    current_symbol^ := token.identifierKind;
+    token := parser_lex(parser^.lexer)
+  end;
+  current_symbol := current_symbol + 1;
+  memset(current_symbol, 0, #size(Identifier));
+
+  token := parser_lex(parser^.lexer);
+
+  return result
+end;
+
+proc parse_import_part(parser: ^Parser) -> ^^AstImportStatement;
+var
+  token: LexerToken;
+  import_statement: ^^AstImportStatement;
+  result: ^^AstImportStatement;
+  import_count: Word;
+begin
+  token := lexer_current(parser^.lexer);
+  result := malloc(#size(^AstImportStatement));
+  import_statement := result;
+  import_count := 0u;
+
+  while token.kind = lexerKindFrom do
+    import_count := import_count + 1u;
+
+    result := realloc(result, #size(^AstImportStatement) * (import_count + 1u));
+    import_statement := result + (import_count - 1u);
+
+    import_statement^ := parse_import_statement(parser);
+    token := lexer_current(parser^.lexer)
+  end;
+  if import_count > 0u then
+    import_statement := import_count + 1
+  end;
+  import_statement^ := nil;
+
+  return result
+end;
+
+proc parse_literal(parser: ^Parser) -> ^AstLiteral;
+var
+  literal: ^AstLiteral;
+  token: LexerToken;
+begin
+  literal := nil;
+  token := lexer_current(parser^.lexer);
+
+  if token.kind = lexerKindInteger then
+    NEW(literal);
+
+    literal^.kind := AstLiteralKind.integer;
+    literal^.integer := token.integerKind
+  end;
+  if (token.kind = lexerKindCharacter) or (token.kind = lexerKindString) then
+    NEW(literal);
+
+    literal^.kind := AstLiteralKind.string;
+    literal^.string := token.stringKind
+  end;
+  if token.kind = lexerKindNull then
+    NEW(literal);
+
+    literal^.kind := AstLiteralKind.null
+  end;
+  if token.kind = lexerKindBoolean then
+    NEW(literal);
+
+    literal^.kind := AstLiteralKind.boolean;
+    literal^.boolean := token.booleanKind
+  end;
+  if literal <> nil then
+    token := parser_lex(parser^.lexer)
+  end;
+
+  return literal
+end;
+
+proc parse_factor(parser: ^Parser) -> ^AstExpression;
+var
+  next_token: LexerToken;
+  result: ^AstExpression;
+  literal: ^AstLiteral;
+begin
+  result := nil;
+  next_token := lexer_current(parser^.lexer);
+
+  literal := parse_literal(parser);
+
+  if (result = nil) & (literal <> nil) then
+    NEW(result);
+
+    result^.kind := AstExpressionKind.literal;
+    result^.literal := literal
+  end;
+  if (result = nil) & (next_token.kind = lexerKindMinus) then
+    NEW(result);
+    next_token := parser_lex(parser^.lexer);
+
+    result^.kind := AstExpressionKind.unary;
+    result^.unary.operator := AstUnaryOperator.minus;
+    result^.unary.operand := parse_factor(parser)
+  end;
+  if (result = nil) & (next_token.kind = lexerKindTilde) then
+    NEW(result);
+    next_token := parser_lex(parser^.lexer);
+
+    result^.kind := AstExpressionKind.unary;
+    result^.unary.operator := AstUnaryOperator.not;
+    result^.unary.operand := parse_factor(parser)
+  end;
+  if (result = nil) & (next_token.kind = lexerKindLeftParen) then
+    next_token := parser_lex(parser^.lexer);
+    result := parse_expression(parser);
+    if result <> nil then
+      next_token := parser_lex(parser^.lexer)
+    end
+  end;
+  if (result = nil) & (next_token.kind = lexerKindIdentifier) then
+    NEW(result);
+
+    result^.kind := AstExpressionKind.identifier;
+    result^.identifier := next_token.identifierKind;
+
+    next_token := parser_lex(parser^.lexer)
+  end;
+
+  return result
+end;
+
+proc parse_designator(parser: ^Parser) -> ^AstExpression;
+var
+  next_token: LexerToken;
+  inner_expression: ^AstExpression;
+  designator: ^AstExpression;
+  arguments: ^^AstExpression;
+  handled: Bool;
+begin
+  designator := parse_factor(parser);
+  handled := designator <> nil;
+  next_token := lexer_current(parser^.lexer);
+
+  while handled do
+    inner_expression := designator;
+    handled := false;
+
+    if ~handled & (next_token.kind = lexerKindHat) then
+      NEW(designator);
+
+      designator^.kind := AstExpressionKind.dereference;
+      designator^.reference := inner_expression;
+
+      next_token := parser_lex(parser^.lexer);
+      handled := true
+    end;
+    if ~handled & (next_token.kind = lexerKindLeftSquare) then
+      NEW(designator);
+      next_token := parser_lex(parser^.lexer);
+
+      designator^.kind := AstExpressionKind.array_access;
+      designator^.array_access.array := inner_expression;
+      designator^.array_access.index := parse_expression(parser);
+
+      next_token := parser_lex(parser^.lexer);
+      handled := true
+    end;
+    if ~handled & (next_token.kind = lexerKindDot) then
+      NEW(designator);
+      next_token := parser_lex(parser^.lexer);
+
+      designator^.kind := AstExpressionKind.field_access;
+      designator^.field_access.aggregate := inner_expression;
+      designator^.field_access.field := next_token.identifierKind;
+
+      next_token := parser_lex(parser^.lexer);
+      handled := true
+    end;
+    if ~handled & (next_token.kind = lexerKindLeftParen) then
+      NEW(designator);
+      next_token := parser_lex(parser^.lexer);
+
+      designator^.kind := AstExpressionKind.call;
+      designator^.call.callable := inner_expression;
+      designator^.call.argument_count := 0;
+      designator^.call.arguments := nil;
+
+      if next_token.kind <> lexerKindRightParen then
+        designator^.arguments := malloc(#size(^AstExpression));
+        designator^.argument_count := 1;
+        designator^.arguments^ := parse_expression(parser);
+
+        next_token := lexer_current(parser^.lexer);
+
+        while next_token.kind = lexerKindComma do
+          next_token := parser_lex(parser^.lexer);
+
+          designator^.argument_count := designator^.argument_count + 1;
+          designator^.arguments := realloc(designator^.arguments, #size(^AstExpression) * designator^.argument_count);
+          arguments := designator^.arguments + (designator^.argument_count - 1u);
+          arguments^ := parse_expression(parser);
+
+          next_token := lexer_current(parser^.lexer)
+        end
+      end;
+
+      next_token := parser_lex(parser^.lexer);
+      handled := true
+    end
+  end;
+
+  return designator
+end;
+
+proc parse_binary_expression(parser: ^Parser, left: ^AstExpression, operator: AstBinaryOperator) -> ^AstExpression;
+var
+  next_token: LexerToken;
+  result: ^AstExpression;
+  right: ^AstExpression;
+begin
+  next_token := parser_lex(parser^.lexer);
+  right := parse_designator(parser);
+  result := nil;
+
+  if right <> nil then
+    NEW(result);
+    result^.kind := AstExpressionKind.binary;
+    result^.binary.operator := operator;
+    result^.binary.lhs := left;
+    result^.binary.rhs := right
+  end;
+
+  return result
+end;
+
+proc parse_expression(parser: ^Parser) -> ^AstExpression;
+var
+  next_token: LexerToken;
+  left: ^AstExpression;
+  result: ^AstExpression;
+  written_bytes: Word;
+begin
+  left := parse_designator(parser);
+  result := nil;
+  next_token := lexer_current(parser^.lexer);
+
+  if left <> nil then
+    if (result = nil) & (next_token.kind = lexerKindNotEqual) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.not_equals)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindEqual) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.equals)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindGreaterThan) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.greater)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindLessThan) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.less)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindGreaterEqual) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.greater_equal)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindLessEqual) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.less_equal)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindAnd) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.conjunction)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindOr) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.disjunction)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindMinus) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.subtraction)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindPlus) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.sum)
+    end;
+    if (result = nil) & (next_token.kind = lexerKindAsterisk) then
+      result := parse_binary_expression(parser, left, AstBinaryOperator.multiplication)
+    end
+  end;
+  if (result = nil) & (left <> nil) then
+    result := left
+  end;
+
+  return result
+end;
+
+proc parse_return_statement(parser: ^Parser) -> ^AstStatement;
+var
+  token: LexerToken;
+  result: ^AstStatement;
+begin
+  NEW(result);
+  result^.kind := AstStatementKind.return_statement;
+
+  token := parser_lex(parser^.lexer);
+  result^.return_statement := parse_expression(parser);
+
+  return result
+end;
+
+proc parse_assignment_statement(parser: ^Parser, assignee: ^AstExpression) -> ^AstStatement;
+var
+  token: LexerToken;
+  result: ^AstStatement;
+begin
+  NEW(result);
+  result^.kind := AstStatementKind.assignment_statement;
+  result^.assignment_statement.assignee := assignee;
+
+  token := parser_lex(parser^.lexer);
+  result^.assignment_statement.assignment := parse_expression(parser);
+
+  return result
+end;
+
+proc parse_call_statement(parser: ^Parser, call: ^AstExpression) -> ^AstStatement;
+var
+  result: ^AstStatement;
+begin
+  NEW(result);
+  result^.kind := AstStatementKind.call_statement;
+  result^.call_statement := call;
+
+  return result
+end;
+
+proc parse_compound_statement(parser: ^Parser) -> AstCompoundStatement;
+var
+  result: AstCompoundStatement;
+  token: LexerToken;
+  current_statement: ^^AstStatement;
+  old_count: Word;
+begin
+  result.count := 0u;
+  result.statements := nil;
+
+  token := lexer_current(parser^.lexer);
+
+  while token.kind <> lexerKindEnd do
+    old_count := result.count;
+    result.count := result.count + 1u;
+
+    result.statements := realloc(result.statements, #size(^AstStatement) * result.count);
+    current_statement := result.statements + old_count;
+
+    current_statement^ := parse_statement(parser);
+
+    token := lexer_current(parser^.lexer)
+  end;
+
+  return result
+end;
+
+proc parse_statement(parser: ^Parser) -> ^AstStatement;
+var
+  token: LexerToken;
+  statement: ^AstStatement;
+  designator: ^AstExpression;
+begin
+  statement := nil;
+  token := parser_lex(parser^.lexer);
+
+  if token.kind = lexerKindIf then
+    statement := parse_if_statement(parser)
+  end;
+  if token.kind = lexerKindWhile then
+    statement := parse_while_statement(parser)
+  end;
+  if token.kind = lexerKindReturn then
+    statement := parse_return_statement(parser)
+  end;
+  if token.kind = lexerKindIdentifier then
+    designator := parse_designator(parser);
+    token := lexer_current(parser^.lexer);
+
+    if token.kind = lexerKindAssignment then
+      statement := parse_assignment_statement(parser, designator)
+    end;
+    if token.kind <> lexerKindAssignment then
+      statement := parse_call_statement(parser, designator)
+    end
+  end;
+  return statement
+end;
+
+proc parse_if_statement(parser: ^Parser) -> ^AstStatement;
+var
+  token: LexerToken;
+  result: ^AstStatement;
+begin
+  NEW(result);
+  result^.kind := AstStatementKind.if_statement;
+
+  token := parser_lex(parser^.lexer);
+  result^.if_statement.condition := parse_expression(parser);
+  result^.if_statement.branch := parse_compound_statement(parser);
+
+  token := parser_lex(parser^.lexer);
+  return result
+end;
+
+proc parse_while_statement(parser: ^Parser) -> ^AstStatement;
+var
+  token: LexerToken;
+  result: ^AstStatement;
+begin
+  NEW(result);
+  result^.kind := AstStatementKind.while_statement;
+
+  token := parser_lex(parser^.lexer);
+  result^.while_statement.condition := parse_expression(parser);
+  result^.while_statement.body := parse_compound_statement(parser);
+
+  token := parser_lex(parser^.lexer);
+  return result
+end;
+
+proc parse_statement_part(parser: ^Parser) -> AstCompoundStatement;
+var
+  token: LexerToken;
+  compound: AstCompoundStatement;
+begin
+  compound.count := 0;
+  compound.statements := nil;
+  token := lexer_current(parser^.lexer);
+
+  if token.kind = lexerKindBegin then
+    compound := parse_compound_statement(parser)
+  end;
+
+  return compound
+end;
+
+proc parse_procedure_heading(parser: ^Parser) -> ^AstProcedureDeclaration;
+var
+  token: LexerToken;
+  declaration: ^AstProcedureDeclaration;
+  parameter_index: Word;
+  current_parameter: ^AstTypedDeclaration;
+begin
+  NEW(declaration);
+
+  token := parser_lex(parser^.lexer);
+  declaration^.name := token.identifierKind;
+
+  token := parser_lex(parser^.lexer);
+
+  declaration^.parameters := nil;
+  declaration^.parameter_count := 0u;
+
+  token := parser_lex(parser^.lexer);
+  while token.kind <> lexerKindRightParen do
+    parameter_index := declaration^.parameter_count;
+    declaration^.parameter_count := declaration^.parameter_count + 1;
+    declaration^.parameters := realloc(declaration^.parameters, #size(AstTypedDeclaration) * declaration^.parameter_count);
+
+    current_parameter := declaration^.parameters + parameter_index;
+
+    current_parameter^.identifier := token.identifierKind;
+
+    token := parser_lex(parser^.lexer);
+    token := parser_lex(parser^.lexer);
+
+    current_parameter^.type_expression := parse_type_expression(parser);
+
+    token := parser_lex(parser^.lexer);
+    if token.kind = lexerKindComma then
+      token := parser_lex(parser^.lexer)
+    end
+  end;
+  token := parser_lex(parser^.lexer);
+  declaration^.return_type := nil;
+
+  (* Check for the return type and write it. *)
+  if token.kind = lexerKindArrow then
+    token := parser_lex(parser^.lexer);
+    declaration^.return_type := parse_type_expression(parser);
+    token := parser_lex(parser^.lexer)
+  end;
+  token := parser_lex(parser^.lexer);
+
+  return declaration
+end;
+
+proc parse_procedure_declaration(parser: ^Parser) -> ^AstProcedureDeclaration;
+var
+  token: LexerToken;
+  declaration: ^AstProcedureDeclaration;
+begin
+  declaration := parse_procedure_heading(parser);
+
+  declaration^.constants := parse_constant_part(parser);
+  declaration^.variables := parse_variable_part(parser);
+  declaration^.statements := parse_statement_part(parser);
+
+  token := parser_lex(parser^.lexer);
+  token := parser_lex(parser^.lexer);
+
+  return declaration
+end;
+
+proc parse_procedure_part(parser: ^Parser) -> ^^AstProcedureDeclaration;
+var
+  token: LexerToken;
+  current_declaration: ^^AstProcedureDeclaration;
+  result: ^^AstProcedureDeclaration;
+  declaration_count: Word;
+  declaration_index: Word;
+begin
+  token := lexer_current(parser^.lexer);
+  declaration_count := 0u;
+  declaration_index := 0u;
+
+  result := malloc(#size(^AstProcedureDeclaration));
+
+  while token.kind = lexerKindProc do
+    declaration_count := declaration_count + 1u;
+    result := realloc(result, #size(^AstProcedureDeclaration) * (declaration_count + 1));
+    current_declaration := result + declaration_index;
+
+    current_declaration^ := parse_procedure_declaration(parser);
+    token := lexer_current(parser^.lexer);
+    declaration_index := declaration_count
+  end;
+  current_declaration := result + declaration_index;
+  current_declaration^ := nil;
+
+  return result
+end;
+
+proc parse_module(parser: ^Parser) -> ^AstModule;
+var
+  token: LexerToken;
+  result: ^AstModule;
+begin
+  NEW(result);
+  token := parser_lex(parser^.lexer);
+  result^.main := true;
+
+  if token.kind = lexerKindModule then
+    result^.main := false
+  end;
+  token := parser_lex(parser^.lexer);
+
+  (* Write the module body. *)
+  token := parser_lex(parser^.lexer);
+
+  result^.imports := parse_import_part(parser);
+  result^.constants := parse_constant_part(parser);
+  result^.types := parse_type_part(parser);
+
+  result^.variables := parse_variable_part(parser);
+  result^.procedures := parse_procedure_part(parser);
+  result^.statements := parse_statement_part(parser);
+
+  token := parser_lex(parser^.lexer);
+  token := parser_lex(parser^.lexer);
+
+  return result
+end;
+
+proc parse*(lexer: ^Lexer) -> ^AstModule;
+var
+  parser: Parser;
+begin
+  parser.lexer := lexer;
+
+  return parse_module(@parser)
+end;
+
+end.