feat: 添加If语句及块语句解析支持

src/Ast/Ast.hpp

@@ -15,4 +15,5 @@
 #include <Ast/Expr/PrefixExpr.hpp>
 
 #include <Ast/Stmt/ExprStmt.hpp>
+#include <Ast/Stmt/IfStmt.hpp>
 #include <Ast/Stmt/VarDecl.hpp>

src/Ast/Base.hpp

@@ -15,10 +15,11 @@ namespace Fig
 {
     enum class AstType : std::uint8_t
     {
-        AstNode, // 基类
-        Program, // 程序
-        Expr,    // 表达式
-        Stmt,    // 语句
+        AstNode,   // 基类
+        Program,   // 程序
+        Expr,      // 表达式
+        Stmt,      // 语句
+        BlockStmt, // 块语句
 
         /* Expressions */
         IdentiExpr,  // 标识符表达式
@@ -30,8 +31,10 @@ namespace Fig
         CallExpr,  // 后缀表达式，函数调用
 
         /* Statements */
-        ExprStmt, // 表达式语句，如 println(1)
-        VarDecl,  // 变量声明
+        ExprStmt,   // 表达式语句，如 println(1)
+        VarDecl,    // 变量声明
+        IfStmt,     // If语句
+        ElseIfStmt, // ElseIf语句，不准悬空
     };
     struct AstNode
     {
@@ -81,7 +84,29 @@ namespace Fig
 
         virtual String toString() const override
         {
-            return "Program";
+            return "<Program>";
+        }
+    };
+
+    struct BlockStmt final : public Stmt
+    {
+        DynArray<Stmt *> nodes;
+        BlockStmt()
+        {
+            type = AstType::BlockStmt;
+        }
+        BlockStmt(DynArray<Stmt *> _nodes)
+        {
+            type  = AstType::BlockStmt;
+            nodes = std::move(_nodes);
+            if (!_nodes.empty())
+            {
+                location = std::move(_nodes.back()->location);
+            }
+        }
+        virtual String toString() const override
+        {
+            return "<BlockStmt>";
         }
     };
 }; // namespace Fig

src/Ast/Stmt/IfStmt.hpp

@@ -0,0 +1,69 @@
+/*!
+    @file src/Ast/Stmt/IfStmt.hpp
+    @brief IfStmt定义
+    @author PuqiAR (im@puqiar.top)
+    @date 2026-02-20
+*/
+
+#pragma once
+
+#include <Ast/Base.hpp>
+
+namespace Fig
+{
+    struct ElseIfStmt final : public Stmt
+    {
+        Expr      *cond;
+        BlockStmt *consequent;
+
+        ElseIfStmt()
+        {
+            type = AstType::ElseIfStmt;
+        }
+
+        ElseIfStmt(Expr *_cond, BlockStmt *_consequent, SourceLocation _location) :
+            cond(_cond), consequent(_consequent)
+        {
+            type     = AstType::ElseIfStmt;
+            location = std::move(_location);
+        }
+
+        virtual String toString() const override
+        {
+            return std::format("<ElseIf ({}) then {}>", cond->toString(), consequent->toString());
+        }
+    };
+
+    struct IfStmt final : public Stmt
+    {
+        Expr                  *cond;
+        BlockStmt             *consequent;
+        DynArray<ElseIfStmt *> elifs;
+        BlockStmt             *alternate;
+
+        IfStmt()
+        {
+            type = AstType::IfStmt;
+        }
+
+        IfStmt(Expr               *_cond,
+            BlockStmt             *_consequent,
+            DynArray<ElseIfStmt *> _elifs,
+            BlockStmt             *_alternate,
+            SourceLocation         _location) :
+            cond(_cond), consequent(_consequent), elifs(std::move(_elifs)), alternate(_alternate)
+        {
+            type     = AstType::IfStmt;
+            location = std::move(_location);
+        }
+
+        virtual String toString() const override
+        {
+            return std::format("<If ({}) then {}, else if * {}, else {}>",
+                cond->toString(),
+                consequent->toString(),
+                elifs.size(),
+                alternate->toString());
+        }
+    };
+}; // namespace Fig