support function literal, set builtins to global context. great!

include/Ast/FunctionLiteralExpr.hpp

@@ -0,0 +1,47 @@
+#pragma once
+
+#include <Ast/astBase.hpp>
+#include <Ast/functionParameters.hpp>
+#include <fig_string.hpp>
+#include <variant>
+
+namespace Fig::Ast
+{
+    class FunctionLiteralExprAst final : public ExpressionAst
+    {
+    public:
+        FunctionParameters paras;
+        std::variant<BlockStatement, Expression> body;
+
+        FunctionLiteralExprAst(FunctionParameters _paras, BlockStatement _body) :
+            paras(std::move(_paras)), body(std::move(_body))
+        {
+            type = AstType::FunctionLiteralExpr;
+        }
+
+        FunctionLiteralExprAst(FunctionParameters _paras, Expression _exprBody) :
+            paras(std::move(_paras)), body(std::move(_exprBody))
+        {
+            type = AstType::FunctionLiteralExpr;
+        }
+
+        bool isExprMode() const
+        {
+            return std::holds_alternative<Expression>(body);
+        }
+
+        BlockStatement &getBlockBody()
+        {
+            return std::get<BlockStatement>(body);
+        }
+
+        Expression &getExprBody()
+        {
+            return std::get<Expression>(body);
+        }
+
+        ~FunctionLiteralExprAst() = default;
+    };
+
+    using FunctionLiteralExpr = std::shared_ptr<FunctionLiteralExprAst>;
+} // namespace Fig::Ast