Forbid redefenition of builtin types

boot/semantic.cc

@@ -52,7 +52,8 @@ namespace boot
     {
         for (type_definition *const type : program->types)
         {
-            if (!this->unresolved.insert({ type->identifier, std::make_shared<alias_type>() }).second)
+            if (!this->unresolved.insert({ type->identifier, std::make_shared<alias_type>(type->identifier) }).second
+                    || this->symbols->contains(type->identifier))
             {
                 add_error<already_declared_error>(type->identifier, this->input_file, type->position());
             }
@@ -61,6 +62,11 @@ namespace boot
         {
             type->accept(this);
         }
+        for (auto& unresolved : this->unresolved)
+        {
+            auto info = std::make_shared<type_info>(type_info(type(unresolved.second)));
+            this->symbols->enter(std::move(unresolved.first), info);
+        }
     }
 
     void declaration_visitor::visit(type_definition *definition)
@@ -79,7 +85,7 @@ namespace boot
         {
             this->current_type = type(unresolved_alias->second);
         }
-        else if (auto from_symbol_table = this->symbols.lookup(type_expression->name))
+        else if (auto from_symbol_table = this->symbols->lookup(type_expression->name))
         {
             this->current_type = from_symbol_table->is_type()->symbol;
         }

boot/symbol.cc

@@ -247,6 +247,11 @@ namespace boot
         return tag == type_tag::empty;
     }
 
+    alias_type::alias_type(const std::string& name)
+        : name(name), reference()
+    {
+    }
+
     pointer_type::pointer_type(type base)
         : base(base)
     {

gcc/Make-lang.in

@@ -136,7 +136,7 @@ elna.stagefeedback: stagefeedback-start
 	-mv elna/*$(objext) stagefeedback/elna
 
 ELNA_INCLUDES = -I $(srcdir)/elna/include -I elna/generated
-ELNA_CXXFLAGS = -std=c++14
+ELNA_CXXFLAGS = -std=c++17
 
 elna/%.o: elna/boot/%.cc elna/generated/parser.hh elna/generated/location.hh
 	$(COMPILE) $(ELNA_CXXFLAGS) $(ELNA_INCLUDES) $<

include/elna/boot/semantic.h

@@ -51,7 +51,7 @@ namespace boot
     class declaration_visitor final : public empty_visitor, public error_container
     {
         type current_type;
-        symbol_table symbols;
+        std::shared_ptr<symbol_table> symbols;
 
     public:
         std::unordered_map<std::string, std::shared_ptr<alias_type>> unresolved;

include/elna/boot/symbol.h

@@ -85,7 +85,10 @@ namespace boot
 
     struct alias_type
     {
+        const std::string name;
         type reference;
+
+        explicit alias_type(const std::string& name);
     };
 
     struct pointer_type
@@ -173,22 +176,30 @@ namespace boot
 
         iterator begin()
         {
-            return entries.begin();
+            return this->entries.begin();
         }
 
         iterator end()
         {
-            return entries.end();
+            return this->entries.end();
         }
 
         const_iterator cbegin() const
         {
-            return entries.cbegin();
+            return this->entries.cbegin();
         }
 
         const_iterator cend() const
         {
-            return entries.cend();
+            return this->entries.cend();
+        }
+
+        /**
+         * \return Symbol count in the current scope.
+         */
+        std::size_t size() const
+        {
+            return this->entries.size();
         }
 
         /**
@@ -213,6 +224,15 @@ namespace boot
             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.
          *