feat: 添加函数定义和类型表达式支持，重构解析器以处理新语法(函数定义)

src/Ast/Ast.hpp

@@ -15,6 +15,8 @@
 #include <Ast/Expr/PrefixExpr.hpp>
 
 #include <Ast/Stmt/ExprStmt.hpp>
+#include <Ast/Stmt/FnDefStmt.hpp>
 #include <Ast/Stmt/IfStmt.hpp>
 #include <Ast/Stmt/VarDecl.hpp>
-#include <Ast/Stmt/WhileStmt.hpp>
+#include <Ast/Stmt/WhileStmt.hpp>
+#include <Ast/TypeExpr.hpp>

src/Ast/Base.hpp

@@ -38,6 +38,12 @@ namespace Fig
         IfStmt,     // If语句
         ElseIfStmt, // ElseIf语句，不准悬空，平铺式else if
         WhileStmt,  // while语句
+        FnDefStmt,  // func函数定义语句
+
+        /* Type Expressions */
+        TypeExpr,      // 基类
+        NamedTypeExpr, // 命名类型，支持namespace, std.file这样的
+        // 泛型等...
     };
     struct AstNode
     {
@@ -45,7 +51,16 @@ namespace Fig
         SourceLocation location;
 
         virtual String toString() const = 0;
-        virtual ~AstNode(){};
+        virtual ~AstNode() {};
+    };
+
+    struct TypeExpr : public AstNode
+    {
+        TypeExpr()
+        {
+            type = AstType::TypeExpr;
+        }
+        virtual ~TypeExpr() = default;
     };
 
     struct Program;

src/Ast/Stmt/FnDefStmt.hpp

@@ -0,0 +1,100 @@
+/*!
+    @file src/Ast/Stmt/FnDefStmt.hpp
+    @brief FnDefStmt定义
+    @author PuqiAR (im@puqiar.top)
+    @date 2026-02-25
+*/
+
+#pragma once
+
+#include <Ast/Base.hpp>
+
+namespace Fig
+{
+    struct Param
+    {
+        String         name;
+        SourceLocation location;
+
+        virtual String toString() const = 0;
+    };
+
+    struct PosParam final : public Param
+    {
+        TypeExpr *type;
+        Expr     *defaultValue;
+
+        PosParam() {}
+        PosParam(String _name, TypeExpr *_type, Expr *_defaultValue, SourceLocation _location) :
+            type(_type), defaultValue(_defaultValue)
+        {
+            name = std::move(_name);
+            location = std::move(_location);
+        }
+
+        virtual String toString() const override
+        {
+            return std::format(
+                "<Pos {}: {}{}>",
+                name,
+                (type ? type->toString() : "Any"),
+                (defaultValue ? " =" + defaultValue->toString() : "")
+            );
+        }
+    };
+
+    /*
+        (public) func foo([name: (type) (= default value)]) (-> return type)
+        {
+            ...
+        }
+
+    */
+
+    struct FnDefStmt final : public Stmt
+    {
+        String            name;
+        DynArray<Param *> params;
+        TypeExpr         *returnType;
+        BlockStmt        *body;
+
+        FnDefStmt()
+        {
+            type = AstType::FnDefStmt;
+        }
+
+        FnDefStmt(bool        _isPublic,
+            String            _name,
+            DynArray<Param *> _params,
+            TypeExpr         *_returnType,
+            BlockStmt        *_body,
+            SourceLocation    _location) :
+            name(std::move(_name)), params(std::move(_params)), returnType(_returnType), body(_body)
+        {
+            type     = AstType::FnDefStmt;
+            isPublic = _isPublic;
+            location = std::move(_location);
+        }
+
+        virtual String toString() const override
+        {
+            String pStr;
+            for (const Param *p : params)
+            {
+                if (p != *params.begin())
+                {
+                    pStr += ", ";
+                }
+                pStr += p->toString();
+            }
+            return std::format(
+                "<FnDefStmt {}{}({}) -> {} {{{}}}>",
+                (isPublic ? "public " : ""),
+                name,
+                pStr,
+                (returnType ? returnType->toString() : "Any"),
+                body->toString()
+            );
+        }
+    };
+}; // namespace Fig

src/Ast/Stmt/VarDecl.hpp

@@ -15,7 +15,7 @@ namespace Fig
     struct VarDecl final : public Stmt
     {
         String name;
-        Expr  *typeSpecifier;
+        TypeExpr  *typeSpecifier;
         bool isInfer; // 是否用了 := 类型推断
         Expr  *initExpr;
 
@@ -26,7 +26,7 @@ namespace Fig
             type = AstType::VarDecl;
         }
 
-        VarDecl(bool _isPublic, String _name, Expr *_typeSpecifier, bool _isInfer, Expr *_initExpr, SourceLocation _location) :
+        VarDecl(bool _isPublic, String _name, TypeExpr *_typeSpecifier, bool _isInfer, Expr *_initExpr, SourceLocation _location) :
             name(std::move(_name)),
             typeSpecifier(_typeSpecifier),
             isInfer(_isInfer),

src/Ast/TypeExpr.hpp

@@ -0,0 +1,36 @@
+/*!
+    @file src/Ast/TypeExpr.hpp
+    @brief TypeExpr定义
+    @author PuqiAR (im@puqiar.top)
+    @date 2026-02-25
+*/
+
+#pragma once
+
+#include <Ast/Base.hpp>
+
+namespace Fig
+{
+
+    struct NamedTypeExpr final : public TypeExpr
+    {
+        DynArray<String> path; // {"std", "file"} etc.
+
+        NamedTypeExpr()
+        {
+            type = AstType::NamedTypeExpr;
+        }
+
+        NamedTypeExpr(DynArray<String> _path, SourceLocation _location) :
+            path(std::move(_path))
+        {
+            type = AstType::NamedTypeExpr;
+            location = std::move(_location);
+        }
+
+        virtual String toString() const override
+        {
+            return std::format("<NamedTypeExpr '{}'>", path);
+        }
+    };
+};