Feature/builtin functions

src/language/ast/ASTNodeDataTypeFlattener.cpp

 #include <language/ast/ASTNodeDataTypeFlattener.hpp>
 
 #include <language/PEGGrammar.hpp>
+#include <language/utils/BuiltinFunctionEmbedder.hpp>
 #include <language/utils/FunctionTable.hpp>
 #include <language/utils/SymbolTable.hpp>
 
@@ -33,9 +34,20 @@ ASTNodeDataTypeFlattener::ASTNodeDataTypeFlattener(ASTNode& node, FlattenedDataT
         }
         break;
       }
+      case ASTNodeDataType::builtin_function_t: {
+        uint64_t builtin_function_id   = std::get<uint64_t>(i_function_symbol->attributes().value());
+        auto builtin_function_embedder = node.m_symbol_table->builtinFunctionEmbedderTable()[builtin_function_id];
+
+        const auto& compound_data_type = builtin_function_embedder->getReturnDataType();
+        for (auto data_type : compound_data_type.contentTypeList()) {
+          flattened_datatype_list.push_back({*data_type, node});
+        }
+
+        break;
+      }
         //    LCOV_EXCL_START
       default: {
-        throw ParseError("unexpected function type", node.begin());
+        throw ParseError{"unexpected function type", node.begin()};
       }
         //    LCOV_EXCL_STOP
       }