diff --git a/Fig-VSCode/bin/Fig-LSP.exe b/Fig-VSCode/bin/Fig-LSP.exe
index bc6e237..a5a4bcf 100644
Binary files a/Fig-VSCode/bin/Fig-LSP.exe and b/Fig-VSCode/bin/Fig-LSP.exe differ
diff --git a/src/Ast/Ast.hpp b/src/Ast/Ast.hpp
index e18d5fa..d533941 100644
--- a/src/Ast/Ast.hpp
+++ b/src/Ast/Ast.hpp
@@ -16,4 +16,5 @@
 
 #include <Ast/Stmt/ExprStmt.hpp>
 #include <Ast/Stmt/IfStmt.hpp>
-#include <Ast/Stmt/VarDecl.hpp>
\ No newline at end of file
+#include <Ast/Stmt/VarDecl.hpp>
+#include <Ast/Stmt/WhileStmt.hpp>
\ No newline at end of file
diff --git a/src/Ast/Base.hpp b/src/Ast/Base.hpp
index 17e6011..27b046e 100644
--- a/src/Ast/Base.hpp
+++ b/src/Ast/Base.hpp
@@ -36,7 +36,8 @@ namespace Fig
         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
+        ElseIfStmt, // ElseIf语句，不准悬空，平铺式else if
+        WhileStmt,  // while语句
     };
     struct AstNode
     {
diff --git a/src/Ast/Expr/IdentiExpr.hpp b/src/Ast/Expr/IdentiExpr.hpp
index 1da9471..1c78260 100644
--- a/src/Ast/Expr/IdentiExpr.hpp
+++ b/src/Ast/Expr/IdentiExpr.hpp
@@ -16,9 +16,17 @@ namespace Fig
     {
         String name;
         
-        // Analyzer槽位，存储具体深度
-        int resolvedDepth = -1; // 代表未解析
-        bool isGlobal = false; // 是否全局/对外公开 (isPublic)
+        // Analyzer槽位
+
+        // 寻址空间
+        bool isGlobal = false; // 是否全局, 全局变量存哈希/堆
+
+        // 仅 isGlobal = false 有效
+        int resolvedDepth = -1; // 用于获取闭包上值, -1 代表未解析
+
+        // 栈内槽位
+        int localId = -1; // 局部变量id, -1 未解析
+
 
         IdentiExpr()
         {
diff --git a/src/Ast/Stmt/VarDecl.hpp b/src/Ast/Stmt/VarDecl.hpp
index 781f611..2d94883 100644
--- a/src/Ast/Stmt/VarDecl.hpp
+++ b/src/Ast/Stmt/VarDecl.hpp
@@ -19,6 +19,8 @@ namespace Fig
         bool isInfer; // 是否用了 := 类型推断
         Expr  *initExpr;
 
+        int localId = -1;
+
         VarDecl()
         {
             type = AstType::VarDecl;
diff --git a/src/Ast/Stmt/WhileStmt.hpp b/src/Ast/Stmt/WhileStmt.hpp
new file mode 100644
index 0000000..0a1bc31
--- /dev/null
+++ b/src/Ast/Stmt/WhileStmt.hpp
@@ -0,0 +1,37 @@
+/*!
+    @file src/Ast/Stmt/WhileStmt.hpp
+    @brief WhileStmt定义
+    @author PuqiAR (im@puqiar.top)
+    @date 2026-02-24
+*/
+
+#pragma once
+
+#include <Ast/Base.hpp>
+
+namespace Fig
+{
+    struct WhileStmt final : public Stmt
+    {
+        Expr *cond;
+        BlockStmt *body;
+
+        WhileStmt()
+        {
+            type = AstType::WhileStmt;
+        }
+
+        WhileStmt(Expr *_cond, BlockStmt *_body, SourceLocation _location) :
+            cond(_cond),
+            body(_body)
+        {
+            type = AstType::WhileStmt;
+            location = std::move(_location);
+        }
+
+        virtual String toString() const override
+        {
+            return std::format("<WhileStmt ({}) {{{}}}>", cond->toString(), body->toString());
+        }
+    };
+}; // namespace Fig
\ No newline at end of file
diff --git a/src/Compiler/Compiler.cpp b/src/Compiler/Compiler.cpp
index ce0fc2d..4807703 100644
--- a/src/Compiler/Compiler.cpp
+++ b/src/Compiler/Compiler.cpp
@@ -16,7 +16,7 @@ namespace Fig
 
         for (Stmt *stmt : program->nodes)
         {
-            const auto &result = CompileStmt(static_cast<Stmt *>(stmt));
+            auto result = compileStmt(static_cast<Stmt *>(stmt));
             if (!result)
             {
                 return std::unexpected(result.error());
diff --git a/src/Compiler/Compiler.hpp b/src/Compiler/Compiler.hpp
index 17d4be7..014b55e 100644
--- a/src/Compiler/Compiler.hpp
+++ b/src/Compiler/Compiler.hpp
@@ -29,12 +29,14 @@ namespace Fig
 
     struct LocalVar
     {
-        bool         isPublic; // 是否向上级/同级其他域公开
-        String       name;
-        std::uint8_t reg;   // 寄存器(相对 frame base 的寄存器 id)
-        int          depth; // 作用域深度
+        int          localId; // AST 传来的纯数字 ID
+        std::uint8_t reg;     // 分配到的物理寄存器 ID
+        int          depth;   // 物理作用域深度(用于 EndScope 释放寄存器)
     };
 
+    static constexpr int MAX_LOCALS = 250;
+    static constexpr int MAX_CONSTANTS = UINT16_MAX;
+
     // 任何跨函数、跨模块的编译，都压入弹出这个 State
     struct FuncState
     {
@@ -46,9 +48,12 @@ namespace Fig
         int                scopeDepth = 0;
         DynArray<LocalVar> locals;
 
+        std::uint8_t fastRegMap[UINT8_MAX + 1]; // 256, 索引 = localId, 值 = 寄存器 id
+
         FuncState(String _name, FuncState *enc = nullptr) : name(std::move(_name)), enclosing(enc)
         {
             proto = new Proto();
+            std::fill_n(fastRegMap, 256, UINT8_MAX); // 255代表未分配
         }
         // 注意：这里不 delete proto，因为 proto 是要作为编译产物吐出去的
     };
@@ -100,7 +105,7 @@ namespace Fig
 
         std::uint8_t AllocReg()
         {
-            if (current->freeReg >= 250)
+            if (current->freeReg >= 255)
             {
                 assert(false && "Register overflow!");
             }
@@ -137,6 +142,13 @@ namespace Fig
         std::uint16_t AddConstant(Value v)
         {
             // TODO: 查重
+            auto it =
+                std::find(current->proto->constants.begin(), current->proto->constants.end(), v);
+            if (it != current->proto->constants.end()) 
+            {
+                return std::distance(current->proto->constants.begin(), it);
+            }
+
             current->proto->constants.push_back(v);
             return static_cast<std::uint16_t>(current->proto->constants.size() - 1);
         }
@@ -156,73 +168,18 @@ namespace Fig
             }
         }
 
-        bool HasLocalInCurrentScope(const String &name)
-        {
-            // 逆向查重
-            for (auto it = current->locals.rbegin(); it != current->locals.rend(); ++it)
-            {
-                if (it->depth < current->scopeDepth)
-                    break; // 已经超出了当前深度，提前阻断
-                if (it->name == name)
-                    return true;
-            }
-            return false;
-        }
-
-        bool HasLocal(const String &name)
-        {
-            for (auto it = current->locals.rbegin(); it != current->locals.rend(); ++it)
-            {
-                if (it->name == name)
-                {
-                    if (it->depth == current->scopeDepth)
-                    {
-                        return true; // 同级不管 public直接捕获
-                    }
-                    else if (it->isPublic)
-                    {
-                        return true; // 不同级变量 public才能被捕捉
-                    }
-                }
-            }
-            return false;
-        }
-
-        std::uint8_t ResolveLocal(const String &name)
-        {
-            // 变量遮蔽: 永远先使用同级已有的变量, 所以逆向遍历
-            for (auto it = current->locals.rbegin(); it != current->locals.rend(); ++it)
-            {
-                if (it->name == name)
-                {
-                    if (it->depth < current->scopeDepth && !it->isPublic)
-                    {
-                        assert(
-                            false
-                            && "ResolveLocal: Attempt to access a private variable from an outer scope!");
-                    }
-
-                    return it->reg;
-                }
-            }
-
-            // 如果在本 Frame 没找到，那就是外层函数的变量 (闭包 Upvalue) 或者全局变量 (Global)。
-            assert(
-                false
-                && "ResolveLocal: Variable not found in current frame (Upvalue/Global not implemented yet)!");
-            return UINT8_MAX;
-        }
-
-        std::uint8_t DeclareLocal(bool isPublic, const String &name)
+        std::uint8_t DeclareLocal(int localId)
         {
             std::uint8_t reg = AllocReg();
-            current->locals.push_back(LocalVar{isPublic, name, reg, current->scopeDepth});
+            current->locals.push_back(LocalVar{localId, reg, current->scopeDepth});
+            current->fastRegMap[localId] = reg;
             return reg;
         }
 
-        std::uint8_t DeclareLocal(bool isPublic, const String &name, std::uint8_t reg)
+        std::uint8_t DeclareLocal(int localId, std::uint8_t reg) // 表示复用哪个寄存器
         {
-            current->locals.push_back(LocalVar{isPublic, name, reg, current->scopeDepth});
+            current->locals.push_back(LocalVar{localId, reg, current->scopeDepth});
+            current->fastRegMap[localId] = reg;
             return reg;
         }
 
@@ -261,23 +218,25 @@ namespace Fig
             return location;
         }
 
-        Result<std::uint8_t, Error> CompileIdentiExpr(IdentiExpr *);
-        Result<std::uint8_t, Error> CompileLiteral(LiteralExpr *);
+        Result<std::uint8_t, Error> compileIdentiExpr(IdentiExpr *);
+        Result<std::uint8_t, Error> compileLiteral(LiteralExpr *);
 
-        Result<std::uint8_t, Error> CompileAssignment(
+        Result<std::uint8_t, Error> compileAssignment(
             InfixExpr *); // 编译赋值，由 CompileInfixExpr调用
-        Result<std::uint8_t, Error> CompileInfixExpr(InfixExpr *);
+        Result<std::uint8_t, Error> compileInfixExpr(InfixExpr *);
 
-        Result<std::uint8_t, Error> CompileLeftValue(
+        Result<std::uint8_t, Error> compileLeftValue(
             Expr *); // 左值对象，可以是变量、结构体字段或模块对象
 
-        Result<std::uint8_t, Error> CompileExpr(Expr *);
+        Result<std::uint8_t, Error> compileExpr(Expr *);
 
         /* Statements */
-        Result<void, Error> CompileVarDecl(VarDecl *);
-        Result<void, Error> CompileBlockStmt(BlockStmt *);
-        Result<void, Error> CompileIfStmt(IfStmt *);
-        Result<void, Error> CompileStmt(Stmt *);
+        Result<void, Error> compileVarDecl(VarDecl *);
+        Result<void, Error> compileBlockStmt(BlockStmt *);
+        Result<void, Error> compileIfStmt(IfStmt *);
+        Result<void, Error> compileWhileStmt(WhileStmt *);
+
+        Result<void, Error> compileStmt(Stmt *);
     };
 
     inline void DisassembleInstruction(Instruction inst, std::size_t index)
diff --git a/src/Compiler/ExprCompiler.cpp b/src/Compiler/ExprCompiler.cpp
index a983cef..ec96d9d 100644
--- a/src/Compiler/ExprCompiler.cpp
+++ b/src/Compiler/ExprCompiler.cpp
@@ -9,18 +9,18 @@
 
 namespace Fig
 {
-    Result<std::uint8_t, Error> Compiler::CompileIdentiExpr(IdentiExpr *ie)
+    Result<std::uint8_t, Error> Compiler::compileIdentiExpr(IdentiExpr *ie)
     {
-        // if (!HasLocal(ie->name))
-        // {
-        //     return std::unexpected(Error(ErrorType::UseUndeclaredIdentifier,
-        //         std::format("`{}` has not been defined", ie->name),
-        //         "none",
-        //         makeSourceLocation(ie)));
-        // }
-        return ResolveLocal(ie->name);
+        // TODO: 处理全局变量和闭包 Upvalue
+        std::uint8_t targetReg = current->fastRegMap[ie->localId];
+
+        if (targetReg == UINT8_MAX)
+        {
+            assert(false && "Compiler Bug: Encountered unmapped localId in fastRegMap!");
+        }
+        return targetReg;
     }
-    Result<std::uint8_t, Error> Compiler::CompileLiteral(
+    Result<std::uint8_t, Error> Compiler::compileLiteral(
         LiteralExpr *lit) // 编译字面量, 负责转换 token -> Value
     {
         const Token &token  = lit->token;
@@ -47,8 +47,8 @@ namespace Fig
         }
         else if (token.type == TokenType::LiteralNumber)
         {
-            // TODO: 更换为无异常手写数字解析版本
-            if (lexeme.contains(U'.'))
+            // TODO: 更换为无异常手写数字解析版本 (charconv也可)
+            if (lexeme.contains(U'.') || lexeme.contains(U'e'))
             {
                 // 非整数
                 double d = std::stod(lexeme.toStdString());
@@ -63,23 +63,34 @@ namespace Fig
         }
 
         std::uint8_t  targetReg = AllocReg();
+
+        if (current->proto->constants.size() >= MAX_CONSTANTS)
+        {
+            return std::unexpected(Error(
+                ErrorType::TooManyConstants,
+                std::format("constant limit exceeded: {}", MAX_CONSTANTS),
+                "How did you write such code? try global variable or split file",
+                makeSourceLocation(lit)
+            ));
+        }
+
         std::uint16_t kIndex    = AddConstant(v);
 
         Emit(Op::iABx(OpCode::LoadK, targetReg, kIndex));
         return targetReg;
     }
-    Result<std::uint8_t, Error> Compiler::CompileAssignment(
+    Result<std::uint8_t, Error> Compiler::compileAssignment(
         InfixExpr *infix) // 编译赋值，由 CompileInfixExpr调用
     {
         // op必须为 =
-        const auto &_lhsReg = CompileLeftValue(infix->left); // 必须为左值对象
+        const auto &_lhsReg = compileLeftValue(infix->left); // 必须为左值对象
         if (!_lhsReg)
         {
             return _lhsReg;
         }
         std::uint8_t lhsReg = *_lhsReg;
 
-        const auto  &_rhsReg = CompileExpr(infix->right);
+        const auto  &_rhsReg = compileExpr(infix->right);
         std::uint8_t rhsReg  = *_rhsReg;
 
         FreeReg(rhsReg);
@@ -119,21 +130,21 @@ namespace Fig
         }
         return lhsReg; // 返回赋值的结果，支持连续赋值
     }
-    Result<std::uint8_t, Error> Compiler::CompileInfixExpr(
+    Result<std::uint8_t, Error> Compiler::compileInfixExpr(
         InfixExpr *infix) // 编译中缀表达式，返回一个存放结果的寄存器 ID
     {
         if (infix->op >= BinaryOperator::Assign && infix->op <= BinaryOperator::BitXorAssign)
         {
-            return CompileAssignment(infix);
+            return compileAssignment(infix);
         }
 
-        const auto &_lhsReg = CompileExpr(infix->left);
+        const auto &_lhsReg = compileExpr(infix->left);
         if (!_lhsReg)
         {
             return _lhsReg;
         }
         std::uint8_t lhsReg  = *_lhsReg;
-        const auto  &_rhsReg = CompileExpr(infix->right);
+        const auto  &_rhsReg = compileExpr(infix->right);
         if (!_rhsReg)
         {
             return _rhsReg;
@@ -171,25 +182,52 @@ namespace Fig
                 break;
             }
 
+            case BinaryOperator::Greater: {
+                Emit(Op::iABC(OpCode::Greater, resultReg, lhsReg, rhsReg));
+                break;
+            }
+
+            case BinaryOperator::GreaterEqual: {
+                Emit(Op::iABC(OpCode::GreaterEqual, resultReg, lhsReg, rhsReg));
+                break;
+            }
+
+            case BinaryOperator::Less: {
+                Emit(Op::iABC(OpCode::Less, resultReg, lhsReg, rhsReg));
+                break;
+            }
+
+            case BinaryOperator::LessEqual: {
+                Emit(Op::iABC(OpCode::LessEqual, resultReg, lhsReg, rhsReg));
+                break;
+            }
+
+            case BinaryOperator::Equal: {
+                Emit(Op::iABC(OpCode::Equal, resultReg, lhsReg, rhsReg));
+                break;
+            }
+
             default: assert(false && "CompileInfixExpr: op unsupported yet");
         }
         return resultReg;
     }
-    Result<std::uint8_t, Error> Compiler::CompileLeftValue(
+    Result<std::uint8_t, Error> Compiler::compileLeftValue(
         Expr *expr) // 左值对象，可以是变量、结构体字段或模块对象
     {
         switch (expr->type)
         {
-            case AstType::IdentiExpr: return CompileIdentiExpr(static_cast<IdentiExpr *>(expr));
+            case AstType::IdentiExpr:
+                return compileIdentiExpr(static_cast<IdentiExpr *>(expr));
+                // TODO: 数组切片(a[0])或对象属性(a.b)
 
             default:
-                return std::unexpected(Error(ErrorType::NotAnLvalue,
-                    std::format("`{}` is not a lvalue, expect a valid lvalue", expr->toString()),
-                    "none",
-                    makeSourceLocation(expr)));
+                // Analyzer 有漏洞（编译器内部
+                // 直接崩溃
+                assert(false && "Compiler Bug: Invalid L-value bypassed Analyzer!");
+                return 0;
         }
     }
-    Result<std::uint8_t, Error> Compiler::CompileExpr(
+    Result<std::uint8_t, Error> Compiler::compileExpr(
         Expr *expr) // 编译表达式，必定返回一个存放结果的寄存器 ID
     {
         switch (expr->type)
@@ -199,12 +237,12 @@ namespace Fig
             case AstType::AstNode: assert(false && "CompileExpr: bad node type"); break;
 
             case AstType::IdentiExpr: {
-                return CompileLeftValue(expr); // 左值直接转换成右值
+                return compileLeftValue(expr); // 左值直接转换成右值
             }
             case AstType::LiteralExpr: {
                 LiteralExpr *lit = static_cast<LiteralExpr *>(expr);
 
-                const auto &result = CompileLiteral(lit);
+                auto result = compileLiteral(lit);
                 if (!result)
                 {
                     return std::unexpected(result.error());
@@ -213,7 +251,7 @@ namespace Fig
                 return targetReg;
             }
             case AstType::InfixExpr: {
-                return CompileInfixExpr(static_cast<InfixExpr *>(expr));
+                return compileInfixExpr(static_cast<InfixExpr *>(expr));
             }
         }
     }
diff --git a/src/Compiler/StmtCompiler.cpp b/src/Compiler/StmtCompiler.cpp
index a7f4b63..10e9407 100644
--- a/src/Compiler/StmtCompiler.cpp
+++ b/src/Compiler/StmtCompiler.cpp
@@ -9,40 +9,40 @@
 
 namespace Fig
 {
-    Result<void, Error> Compiler::CompileVarDecl(VarDecl *varDecl)
+    Result<void, Error> Compiler::compileVarDecl(VarDecl *varDecl)
     {
-        const String &name = varDecl->name;
-        // if (HasLocalInCurrentScope(name))
-        // {
-        //     return std::unexpected(Error(ErrorType::RedeclarationError,
-        //         std::format("variable `{}` has already defined in this scope", name),
-        //         "change its name",
-        //         makeSourceLocation(varDecl)));
-        // }
+        if (current->freeReg > MAX_LOCALS)
+        {
+            return std::unexpected(Error(ErrorType::TooManyLocals,
+                std::format("local limit exceeded: {}", MAX_LOCALS),
+                "try split function or use arrays/structs...",
+                makeSourceLocation(varDecl)));
+        }
+
         std::uint8_t varReg;
         if (varDecl->initExpr)
         {
-            const auto &result = CompileExpr(varDecl->initExpr);
+            auto result = compileExpr(varDecl->initExpr);
             if (!result)
             {
                 return std::unexpected(result.error());
             }
             std::uint8_t resultReg = *result;
-            varReg                 = resultReg; // 复用临时计算结果寄存器
-            DeclareLocal(varDecl->isPublic, name, varReg);
+            varReg = DeclareLocal(varDecl->localId, resultReg); // 复用临时计算结果寄存器
         }
         else
         {
-            varReg = DeclareLocal(varDecl->isPublic, name);
+            varReg = DeclareLocal(varDecl->localId);
         }
+
         return Result<void, Error>();
     }
 
-    Result<void, Error> Compiler::CompileBlockStmt(BlockStmt *blockStmt)
+    Result<void, Error> Compiler::compileBlockStmt(BlockStmt *blockStmt)
     {
         for (Stmt *stmt : blockStmt->nodes)
         {
-            const auto &result = CompileStmt(stmt);
+            auto result = compileStmt(stmt);
             if (!result)
             {
                 return result;
@@ -51,7 +51,7 @@ namespace Fig
         return {};
     }
 
-    Result<void, Error> Compiler::CompileIfStmt(IfStmt *stmt)
+    Result<void, Error> Compiler::compileIfStmt(IfStmt *stmt)
     {
         /*
             if cond1
@@ -97,7 +97,7 @@ namespace Fig
 
         */
         std::vector<int> exitJumps; // 所有分支都要跳到最后，收集所有jump最后回填
-        const auto      &condResult = CompileExpr(stmt->cond);
+        const auto      &condResult = compileExpr(stmt->cond);
         if (!condResult)
         {
             return std::unexpected(condResult.error());
@@ -106,7 +106,7 @@ namespace Fig
         int          jumpToNext = EmitJump(OpCode::JmpIfFalse, condReg);
         FreeReg(condReg);
 
-        const auto &blockResult = CompileStmt(stmt->consequent);
+        const auto &blockResult = compileStmt(stmt->consequent);
         if (!blockResult)
         {
             return blockResult;
@@ -117,7 +117,7 @@ namespace Fig
 
         for (auto *elif : stmt->elifs)
         {
-            const auto &elifCondResult = CompileExpr(elif->cond);
+            const auto &elifCondResult = compileExpr(elif->cond);
             if (!elifCondResult)
                 return std::unexpected(elifCondResult.error());
             std::uint8_t elifCondReg = *elifCondResult;
@@ -125,7 +125,7 @@ namespace Fig
             jumpToNext = EmitJump(OpCode::JmpIfFalse, elifCondReg);
             FreeReg(elifCondReg);
 
-            const auto &blockResult = CompileStmt(elif->consequent);
+            const auto &blockResult = compileStmt(elif->consequent);
             if (!blockResult)
             {
                 return blockResult;
@@ -136,7 +136,7 @@ namespace Fig
 
         if (stmt->alternate)
         {
-            const auto &result = CompileStmt(stmt->alternate);
+            auto result = compileStmt(stmt->alternate);
             if (!result)
             {
                 return result;
@@ -148,31 +148,65 @@ namespace Fig
         }
         return {};
     }
-    Result<void, Error> Compiler::CompileStmt(Stmt *stmt) // 编译语句
+
+    Result<void, Error> Compiler::compileWhileStmt(WhileStmt *stmt)
     {
-        if (stmt->type == AstType::ExprStmt)
+        int beginIns = current->proto->code.size() - 1;
+
+        auto condRegResult = compileExpr(stmt->cond);
+        if (!condRegResult)
         {
-            ExprStmt   *exprStmt = static_cast<ExprStmt *>(stmt);
-            Expr       *expr     = exprStmt->expr;
-            const auto &result   = CompileExpr(expr);
-            if (!result)
-            {
-                return std::unexpected(result.error());
+            return std::unexpected(condRegResult.error());
+        }
+
+        std::uint8_t condReg = *condRegResult;
+
+        int  exitJump   = EmitJump(OpCode::JmpIfFalse, condReg);
+        auto bodyResult = compileBlockStmt(stmt->body);
+
+        if (!bodyResult)
+        {
+            return bodyResult;
+        }
+        Emit(Op::iAsBx(
+            OpCode::Jmp, 0, beginIns - current->proto->code.size())); // 回到开头对condition求值
+        PatchJump(exitJump);
+        return {};
+    }
+
+    Result<void, Error> Compiler::compileStmt(Stmt *stmt) // 编译语句
+    {
+        switch (stmt->type)
+        {
+            case AstType::ExprStmt: {
+                ExprStmt *exprStmt = static_cast<ExprStmt *>(stmt);
+                Expr     *expr     = exprStmt->expr;
+                auto      result   = compileExpr(expr);
+                if (!result)
+                {
+                    return std::unexpected(result.error());
+                }
+                FreeReg(*result);
+                break;
+            }
+
+            case AstType::VarDecl: {
+                return compileVarDecl(static_cast<VarDecl *>(stmt));
+            }
+
+            case AstType::BlockStmt: {
+                return compileBlockStmt(static_cast<BlockStmt *>(stmt));
+            }
+
+            case AstType::IfStmt: {
+                return compileIfStmt(static_cast<IfStmt *>(stmt));
+            }
+
+            case AstType::WhileStmt: {
+                return compileWhileStmt(static_cast<WhileStmt *>(stmt));
             }
-            FreeReg(*result);
-        }
-        else if (stmt->type == AstType::VarDecl)
-        {
-            return CompileVarDecl(static_cast<VarDecl *>(stmt));
-        }
-        else if (stmt->type == AstType::BlockStmt)
-        {
-            return CompileBlockStmt(static_cast<BlockStmt *>(stmt));
-        }
-        else if (stmt->type == AstType::IfStmt)
-        {
-            return CompileIfStmt(static_cast<IfStmt *>(stmt));
         }
+
         return Result<void, Error>();
     }
 }; // namespace Fig
\ No newline at end of file
diff --git a/src/Error/Error.cpp b/src/Error/Error.cpp
index aae2bfc..bed806c 100644
--- a/src/Error/Error.cpp
+++ b/src/Error/Error.cpp
@@ -56,6 +56,9 @@ namespace Fig
             case UseUndeclaredIdentifier: return "UseUndeclaredIdentifier";
             case NotAnLvalue: return "NotAnLvalue";
             case TypeError: return "TypeError";
+
+            case TooManyLocals: return "TooManyLocals";
+            case TooManyConstants: return "TooManyConstants";
                 // default: return "Some one forgot to add case to `ErrorTypeToString`";
         }
     }
diff --git a/src/Error/Error.hpp b/src/Error/Error.hpp
index 6a1948e..9c23e5e 100644
--- a/src/Error/Error.hpp
+++ b/src/Error/Error.hpp
@@ -47,6 +47,10 @@ namespace Fig
         UseUndeclaredIdentifier,
         NotAnLvalue,
         TypeError,
+
+        // compile errors
+        TooManyLocals,
+        TooManyConstants,
     };
 
     const char *ErrorTypeToString(ErrorType type);
diff --git a/src/LSP/FigLSPServer.cpp b/src/LSP/LSPServer.cpp
similarity index 100%
rename from src/LSP/FigLSPServer.cpp
rename to src/LSP/LSPServer.cpp
diff --git a/src/Lexer/LexerTest.cpp b/src/Lexer/LexerTest.cpp
index 915231a..81a5fe1 100644
--- a/src/Lexer/LexerTest.cpp
+++ b/src/Lexer/LexerTest.cpp
@@ -1,6 +1,7 @@
 #include <Error/Error.hpp>
-#include <Token/Token.hpp>
 #include <Lexer/Lexer.hpp>
+#include <Token/Token.hpp>
+
 
 #include <iostream>
 
@@ -24,18 +25,18 @@ int main()
 
     while (true)
     {
-        const auto &result = lexer.NextToken();
+        auto result = lexer.NextToken();
         if (!result.has_value())
         {
             ReportError(result.error(), manager);
             break;
         }
-        const Token &token = *result;
+        const Token  &token  = *result;
         const String &lexeme = manager.GetSub(token.index, token.length);
-        const auto &type = magic_enum::enum_name(token.type);
+        const auto   &type   = magic_enum::enum_name(token.type);
         if (token.type == TokenType::EndOfFile)
         {
-            std::cout << "EOF: " << type  << " at " << token.index << '\n';
+            std::cout << "EOF: " << type << " at " << token.index << '\n';
             break;
         }
         std::cout << lexeme << " --> " << type << '\n';
diff --git a/src/Parser/ExprParser.cpp b/src/Parser/ExprParser.cpp
index 3f6e9cd..522b71d 100644
--- a/src/Parser/ExprParser.cpp
+++ b/src/Parser/ExprParser.cpp
@@ -11,14 +11,16 @@ namespace Fig
 {
     Result<LiteralExpr *, Error> Parser::parseLiteralExpr() // 当前token为literal时调用
     {
-        state                      = State::ParsingLiteralExpr;
+        StateProtector p(this, {State::ParsingLiteralExpr});
+
         const Token &literal_token = consumeToken();
         LiteralExpr *node = new LiteralExpr(literal_token, makeSourceLocation(literal_token));
         return node;
     }
     Result<IdentiExpr *, Error> Parser::parseIdentiExpr() // 当前token为Identifier调用
     {
-        state                   = State::ParsingIdentiExpr;
+        StateProtector p(this, {State::ParsingIdentiExpr});
+
         const Token &identifier = consumeToken();
         IdentiExpr  *node       = new IdentiExpr(
             srcManager.GetSub(identifier.index, identifier.length), makeSourceLocation(identifier));
@@ -27,7 +29,8 @@ namespace Fig
 
     Result<InfixExpr *, Error> Parser::parseInfixExpr(Expr *lhs) // 当前token为 op
     {
-        state                   = State::ParsingInfixExpr;
+        StateProtector p(this, {State::ParsingInfixExpr});
+
         const Token   &op_token = consumeToken();
         BinaryOperator op       = TokenToBinaryOp(op_token);
         BindingPower   rbp      = GetBinaryOpRBp(op);
@@ -45,7 +48,8 @@ namespace Fig
 
     Result<PrefixExpr *, Error> Parser::parsePrefixExpr() // 当前token为op
     {
-        state                  = State::ParsingPrefixExpr;
+        StateProtector p(this, {State::ParsingPrefixExpr});
+
         const Token  &op_token = consumeToken();
         UnaryOperator op       = TokenToUnaryOp(op_token);
 
@@ -64,7 +68,8 @@ namespace Fig
     Result<IndexExpr *, Error> Parser::parseIndexExpr(
         Expr *base) // 由 parseExpression调用, 当前token为 `[`
     {
-        state                       = State::ParsingIndexExpr;
+        StateProtector p(this, {State::ParsingIndexExpr});
+
         const Token &lbracket_token = consumeToken(); // consume `[`
         const auto  &index_result   = parseExpression();
 
@@ -89,7 +94,8 @@ namespace Fig
     Result<CallExpr *, Error> Parser::parseCallExpr(
         Expr *callee) // 由 parseExpression调用, 当前token为 `(`
     {
-        state                     = State::ParsingCallExpr;
+        StateProtector p(this, {State::ParsingCallExpr});
+
         const Token &lparen_token = consumeToken(); // consume `(`
 
         FnCallArgs callArgs;
@@ -137,52 +143,8 @@ namespace Fig
         return new CallExpr(callee, callArgs);
     }
 
-    const std::unordered_set<TokenType> &Parser::getBaseTerminators()
+    Result<Expr *, Error> Parser::parseExpression(BindingPower rbp)
     {
-        static const std::unordered_set<TokenType> baseTerminators = {TokenType::Semicolon,
-            TokenType::RightParen,
-            TokenType::RightBracket,
-            TokenType::RightBrace,
-            TokenType::Comma,
-            TokenType::EndOfFile};
-        return baseTerminators;
-    }
-
-    std::unordered_set<TokenType> &Parser::getTerminators()
-    {
-        /*
-
-        Syntax terminators:
-            ;  )  ]  }  ,  EOF
-        */
-
-        static std::unordered_set<TokenType> terminators(getBaseTerminators());
-        return terminators;
-    }
-
-    void Parser::resetTermintors()
-    {
-        getTerminators() = getBaseTerminators();
-    }
-
-    bool Parser::shouldTerminate()
-    {
-        const Token &token       = currentToken();
-        const auto  &terminators = getTerminators();
-        return terminators.contains(token.type);
-    }
-
-    Result<Expr *, Error> Parser::parseExpression(BindingPower rbp, TokenType stop, TokenType stop2)
-    {
-        if (!getTerminators().contains(stop))
-        {
-            getTerminators().insert(stop);
-        }
-        if (!getTerminators().contains(stop2))
-        {
-            getTerminators().insert(stop2);
-        }
-
         Expr *lhs   = nullptr;
         Token token = currentToken();
 
@@ -191,7 +153,6 @@ namespace Fig
             const auto &lhs_result = parseIdentiExpr();
             if (!lhs_result)
             {
-                resetTermintors();
                 return std::unexpected(lhs_result.error());
             }
             lhs = *lhs_result;
@@ -201,7 +162,6 @@ namespace Fig
             const auto &lhs_result = parseLiteralExpr();
             if (!lhs_result)
             {
-                resetTermintors();
                 return std::unexpected(lhs_result.error());
             }
             lhs = *lhs_result;
@@ -211,7 +171,6 @@ namespace Fig
             const auto &lhs_result = parsePrefixExpr();
             if (!lhs_result)
             {
-                resetTermintors();
                 return std::unexpected(lhs_result.error());
             }
             lhs = *lhs_result;
@@ -222,7 +181,6 @@ namespace Fig
             const auto  &expr_result  = parseExpression(0);
             if (!expr_result)
             {
-                resetTermintors();
                 return expr_result;
             }
             const Token &rparen_token = consumeToken(); // consume `)`
@@ -238,7 +196,6 @@ namespace Fig
 
         if (!lhs)
         {
-            resetTermintors();
             return std::unexpected(Error(ErrorType::ExpectedExpression,
                 "expected expression",
                 "insert expressions",
@@ -252,10 +209,6 @@ namespace Fig
             {
                 break;
             }
-            if (token.type == stop || token.type == stop2)
-            {
-                break;
-            }
 
             if (IsTokenOp(token.type /* isBinary = true */)) // 是否为二元运算符
             {
@@ -268,7 +221,7 @@ namespace Fig
                     break;
                 }
 
-                const auto &result = parseInfixExpr(lhs);
+                auto result = parseInfixExpr(lhs);
                 if (!result)
                 {
                     resetTermintors();
diff --git a/src/Parser/Parser.cpp b/src/Parser/Parser.cpp
index 807f692..a9915af 100644
--- a/src/Parser/Parser.cpp
+++ b/src/Parser/Parser.cpp
@@ -5,7 +5,6 @@
     @date 2026-02-14
 */
 
-
 #include <Parser/Parser.hpp>
 
 namespace Fig
@@ -15,7 +14,7 @@ namespace Fig
         Program *program = new Program;
         while (!isEOF)
         {
-            const auto &result = parseStatement();
+            auto result = parseStatement();
             if (!result)
             {
                 return std::unexpected(result.error());
@@ -29,4 +28,4 @@ namespace Fig
         }
         return program;
     }
-};
\ No newline at end of file
+}; // namespace Fig
\ No newline at end of file
diff --git a/src/Parser/Parser.hpp b/src/Parser/Parser.hpp
index 7921c0e..c325077 100644
--- a/src/Parser/Parser.hpp
+++ b/src/Parser/Parser.hpp
@@ -41,7 +41,7 @@ namespace Fig
             {
                 return buffer[++index];
             }
-            const auto &result = lexer.NextToken();
+            auto result = lexer.NextToken();
             if (!result)
             {
                 ReportError(result.error(), srcManager);
@@ -82,7 +82,7 @@ namespace Fig
             size_t peekIndex = index + lookahead;
             while (peekIndex >= buffer.size() && !isEOF)
             {
-                const auto &result = lexer.NextToken();
+                auto result = lexer.NextToken();
                 if (!result)
                 {
                     ReportError(result.error(), srcManager);
@@ -121,51 +121,146 @@ namespace Fig
             return false;
         }
 
-        inline Error makeUnexpectTokenError(const String &stmtType, const String &expect, const Token &tokenGot, std::source_location loc = std::source_location::current())
+        inline Error makeUnexpectTokenError(const String &stmtType,
+            const String                                 &expect,
+            const Token                                  &tokenGot,
+            std::source_location                          loc = std::source_location::current())
         {
-            return Error(
-                ErrorType::SyntaxError,
-                std::format("expect '{}' in {}, got `{}`", expect, stmtType, magic_enum::enum_name(tokenGot.type)),
+            return Error(ErrorType::SyntaxError,
+                std::format("expect '{}' in {}, got `{}`",
+                    expect,
+                    stmtType,
+                    magic_enum::enum_name(tokenGot.type)),
                 "none",
                 makeSourceLocation(tokenGot),
-                loc
-            );
+                loc);
         }
 
-        inline Error makeExpectSemicolonError(std::source_location loc = std::source_location::current())
+        inline Error makeExpectSemicolonError(
+            std::source_location loc = std::source_location::current())
         {
-            return Error(
-                ErrorType::SyntaxError,
+            return Error(ErrorType::SyntaxError,
                 "expect ';' after statement",
                 "insert ';'",
                 makeSourceLocation(currentToken()),
-                loc
-            );
+                loc);
         }
 
     public:
-        enum class State : std::uint8_t
+        struct State
         {
-            Standby,
+            enum StateType : std::uint8_t
+            {
+                Standby,
 
-            ParsingLiteralExpr,
-            ParsingIdentiExpr,
+                ParsingLiteralExpr,
+                ParsingIdentiExpr,
 
-            ParsingInfixExpr,
-            ParsingPrefixExpr,
+                ParsingInfixExpr,
+                ParsingPrefixExpr,
 
-            ParsingIndexExpr,
-            ParsingCallExpr,
+                ParsingIndexExpr,
+                ParsingCallExpr,
 
-            ParsingVarDecl,
-            ParsingIf,
+                ParsingVarDecl,
+                ParsingIf,
+                ParsingWhile,
 
-        } state;
+            } type                               = StateType::Standby;
+            std::unordered_set<TokenType> stopAt = {};
+        };
 
+    private:
+        const std::unordered_set<TokenType> &getBaseTerminators()
+        {
+            static const std::unordered_set<TokenType> baseTerminators = {TokenType::Semicolon,
+                TokenType::RightParen,
+                TokenType::RightBracket,
+                TokenType::RightBrace,
+                TokenType::Comma,
+                TokenType::EndOfFile};
+            return baseTerminators;
+        }
+
+        std::unordered_set<TokenType>       &getTerminators() // 返回固定的终止符
+        {
+            /*
+                Syntax terminators:
+                ;  )  ]  }  ,  EOF
+            */
+
+            static std::unordered_set<TokenType> terminators(getBaseTerminators());
+            return terminators;
+        }
+
+        void resetTermintors()
+        {
+            getTerminators() = getBaseTerminators();
+        }
+        bool shouldTerminate() // 判断是否终结
+        {
+            const Token &token       = currentToken();
+            const auto  &terminators = getTerminators();
+
+            if (terminators.contains(token.type))
+            {
+                return true;
+            }
+            for (auto it = stateStack.rbegin(); it < stateStack.rend(); ++it)
+            {
+                if (it->stopAt.contains(token.type))
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        DynArray<State> stateStack;
+
+        State &currentState()
+        {
+            return stateStack.back();
+        }
+
+        void pushState(State _state)
+        {
+            stateStack.push_back(std::move(_state));
+        }
+
+        void popState()
+        {
+            if (!stateStack.empty())
+            {
+                stateStack.pop_back();
+            }
+        }
+
+        class StateProtector
+        {
+            Parser *parser;
+
+        public:
+            StateProtector(Parser *p, const State &newState) : parser(p)
+            {
+                parser->pushState(newState);
+            }
+
+            ~StateProtector()
+            {
+                parser->popState();
+            }
+
+            // 禁止拷贝
+            StateProtector(const StateProtector &)            = delete;
+            StateProtector &operator=(const StateProtector &) = delete;
+        };
+
+    public:
         Parser(Lexer &_lexer, SourceManager &_srcManager, String _fileName) :
             lexer(_lexer), srcManager(_srcManager), fileName(std::move(_fileName))
         {
-            state = State::Standby;
+            pushState(State());
         }
 
     private:
@@ -175,33 +270,33 @@ namespace Fig
             return SourceLocation(SourcePosition(line, column, tok.length),
                 fileName,
                 "[internal parser]",
-                magic_enum::enum_name(state).data());
+                magic_enum::enum_name(currentState().type).data());
         }
 
         /* Expressions */
         Result<LiteralExpr *, Error> parseLiteralExpr(); // 当前token为literal时调用
         Result<IdentiExpr *, Error>  parseIdentiExpr();  // 当前token为Identifier调用
 
-        Result<InfixExpr *, Error>  parseInfixExpr(Expr *); // 由 parseExpression递归调用, 当前token为op
-        Result<PrefixExpr *, Error> parsePrefixExpr();      // 由 parseExpression递归调用, 当前token为op
+        Result<InfixExpr *, Error> parseInfixExpr(
+            Expr *);                                   // 由 parseExpression递归调用, 当前token为op
+        Result<PrefixExpr *, Error> parsePrefixExpr(); // 由 parseExpression递归调用, 当前token为op
 
-        Result<IndexExpr *, Error> parseIndexExpr(Expr *); // 由 parseExpression调用, 当前token为 `[`
-        Result<CallExpr *, Error>  parseCallExpr(Expr *);  // 由 parseExpression调用, 当前token为 `(`
+        Result<IndexExpr *, Error> parseIndexExpr(
+            Expr *);                                     // 由 parseExpression调用, 当前token为 `[`
+        Result<CallExpr *, Error> parseCallExpr(Expr *); // 由 parseExpression调用, 当前token为 `(`
 
-        const std::unordered_set<TokenType> &getBaseTerminators();
-        std::unordered_set<TokenType> &getTerminators();  // 返回固定的终止符
-        void resetTermintors();
-        bool                          shouldTerminate(); // 判断是否终结
-
-        Result<Expr *, Error> parseExpression(BindingPower = 0, TokenType stop = TokenType::Semicolon, TokenType stop2 = TokenType::Semicolon);
+        Result<Expr *, Error> parseExpression(BindingPower = 0);
 
         /* Statements */
-        Result<BlockStmt *, Error> parseBlockStmt(); // 当前token为 {
-        Result<VarDecl *, Error> parseVarDecl(bool); // 由 parseStatement调用, 当前token为 var
-        Result<IfStmt *, Error> parseIfStmt(); // 由 parseStatement调用, 当前token is if
-        Result<Stmt *, Error> parseStatement();
+        Result<BlockStmt *, Error> parseBlockStmt();   // 当前token为 {
+        Result<VarDecl *, Error>   parseVarDecl(bool); // 由 parseStatement调用, 当前token为 var
+        Result<IfStmt *, Error>    parseIfStmt();      // 由 parseStatement调用, 当前token为 if
+        Result<WhileStmt *, Error> parseWhileStmt();   // 由 parseStatement调用, 当前token为 while
+        Result<Stmt *, Error>      parseStatement();
 
     public:
         Result<Program *, Error> Parse();
     };
+
+#define SET_STOP_AT(...) currentState().stopAt = {__VA_ARGS__};
 }; // namespace Fig
\ No newline at end of file
diff --git a/src/Parser/ParserTest.cpp b/src/Parser/ParserTest.cpp
index e89e467..e661ce1 100644
--- a/src/Parser/ParserTest.cpp
+++ b/src/Parser/ParserTest.cpp
@@ -16,9 +16,9 @@ int main()
         return 1;
     }
 
-    Lexer lexer(source, fileName);
+    Lexer  lexer(source, fileName);
     Parser parser(lexer, srcManager, fileName);
-    const auto &result = parser.Parse();
+    auto   result = parser.Parse();
     if (!result)
     {
         ReportError(result.error(), srcManager);
diff --git a/src/Parser/StmtParser.cpp b/src/Parser/StmtParser.cpp
index bf14675..785af60 100644
--- a/src/Parser/StmtParser.cpp
+++ b/src/Parser/StmtParser.cpp
@@ -19,14 +19,14 @@ namespace Fig
             {
                 return std::unexpected(Error(ErrorType::SyntaxError,
                     "unclosed braces in block stmt",
-                    "insert `}`",
+                    "insert '}'",
                     location));
             }
             if (match(TokenType::RightBrace))
             {
                 break;
             }
-            const auto &result = parseStatement();
+            auto result = parseStatement();
             if (!result)
             {
                 return std::unexpected(result.error());
@@ -38,7 +38,7 @@ namespace Fig
     Result<VarDecl *, Error> Parser::parseVarDecl(
         bool isPublic) // 由 parseStatement调用, 当前token为 var
     {
-        state = State::ParsingVarDecl;
+        StateProtector p(this, {State::ParsingVarDecl});
 
         SourceLocation location = makeSourceLocation(consumeToken()); // consume `var`
 
@@ -52,7 +52,8 @@ namespace Fig
         Expr *typeSpeicifer = nullptr;
         if (match(TokenType::Colon)) // `:`
         {
-            const auto &result = parseExpression(0, TokenType::Assign, TokenType::Walrus);
+            SET_STOP_AT(TokenType::Walrus, TokenType::Assign);
+            auto result = parseExpression(0);
             if (!result)
             {
                 return std::unexpected(result.error());
@@ -61,10 +62,10 @@ namespace Fig
         }
 
         Expr *initExpr = nullptr;
-        bool isInfer = false;
+        bool  isInfer  = false;
         if (match(TokenType::Assign))
         {
-            const auto &result = parseExpression();
+            auto result = parseExpression();
             if (!result)
             {
                 return std::unexpected(result.error());
@@ -73,22 +74,21 @@ namespace Fig
         }
         else if (match(TokenType::Walrus)) // :=
         {
-            if (typeSpeicifer) // 指定了类型同时使用 := 
+            if (typeSpeicifer) // 指定了类型同时使用 :=
             {
-                return std::unexpected(Error(
-                    ErrorType::SyntaxError,
+                return std::unexpected(Error(ErrorType::SyntaxError,
                     "used type infer but specifying the type",
                     "change `:=` to '='",
                     makeSourceLocation(prevToken()) // :=
-                ));
+                    ));
             }
-            const auto &result = parseExpression();
+            auto result = parseExpression();
             if (!result)
             {
                 return std::unexpected(result.error());
             }
             initExpr = *result;
-            isInfer = true; // 使用类型自动推断 :=
+            isInfer  = true; // 使用类型自动推断 :=
         }
         if (!match(TokenType::Semicolon))
         {
@@ -100,14 +100,16 @@ namespace Fig
 
     Result<IfStmt *, Error> Parser::parseIfStmt() // 由 parseStatement调用, 当前token is if
     {
-        state                   = State::ParsingIf;
+        StateProtector p(this, {State::ParsingIf});
+
         SourceLocation location = makeSourceLocation(consumeToken()); // consume `if`
 
         Expr *cond = nullptr;
         if (match(TokenType::LeftParen)) // match and consume `(`
         {
             const Token &lpToken = prevToken();
-            const auto  &result  = parseExpression(0, TokenType::RightParen, TokenType::LeftBrace);
+            SET_STOP_AT(TokenType::RightParen, TokenType::LeftBrace);
+            const auto &result = parseExpression(0);
             if (!result)
             {
                 return std::unexpected(result.error());
@@ -124,21 +126,21 @@ namespace Fig
         }
         else
         {
-            const auto &result = parseExpression(0, TokenType::LeftBrace);
+            SET_STOP_AT(TokenType::LeftBrace);
+            auto result = parseExpression(0);
             if (!result)
             {
                 return std::unexpected(result.error());
             }
             cond = *result;
         }
-        state = State::ParsingIf;
 
         if (currentToken().type != TokenType::LeftBrace)
         {
             return std::unexpected(
                 makeUnexpectTokenError("IfStmt", "LeftBrace `{`", currentToken()));
         }
-        const auto &result = parseBlockStmt();
+        auto result = parseBlockStmt();
         if (!result)
         {
             return std::unexpected(result.error());
@@ -167,13 +169,13 @@ namespace Fig
                 if (match(TokenType::LeftParen)) // `(`
                 {
                     const Token &lpToken = prevToken();
-                    const auto  &result =
-                        parseExpression(0, TokenType::RightParen, TokenType::LeftBrace);
+
+                    SET_STOP_AT(TokenType::RightParen, TokenType::LeftBrace);
+                    const auto &result = parseExpression(0);
                     if (!result)
                     {
                         return std::unexpected(result.error());
                     }
-                    state = State::ParsingIf;
                     if (!match(TokenType::RightParen))
                     {
                         delete *result;
@@ -186,25 +188,24 @@ namespace Fig
                 }
                 else
                 {
-                    const auto &result = parseExpression(0, TokenType::LeftBrace);
+                    SET_STOP_AT(TokenType::LeftBrace);
+                    auto result = parseExpression(0);
                     if (!result)
                     {
                         return std::unexpected(result.error());
                     }
-                    state = State::ParsingIf;
-                    cond  = *result;
+                    cond = *result;
                 }
                 if (currentToken().type != TokenType::LeftBrace)
                 {
                     return std::unexpected(
                         makeUnexpectTokenError("ElseIfStmt", "LeftBrace `{`", currentToken()));
                 }
-                const auto &result = parseBlockStmt();
+                auto result = parseBlockStmt();
                 if (!result)
                 {
                     return std::unexpected(result.error());
                 }
-                state                  = State::ParsingIf;
                 BlockStmt  *consequent = *result;
                 ElseIfStmt *elif       = new ElseIfStmt(cond, consequent, elseLocation);
                 elifs.push_back(elif);
@@ -224,12 +225,11 @@ namespace Fig
                     return std::unexpected(
                         makeUnexpectTokenError("ElseStmt", "LeftBrace `{`", currentToken()));
                 }
-                const auto &result = parseBlockStmt();
+                auto result = parseBlockStmt();
                 if (!result)
                 {
                     return std::unexpected(result.error());
                 }
-                state     = State::ParsingIf;
                 alternate = *result;
             }
         }
@@ -237,9 +237,68 @@ namespace Fig
         return ifStmt;
     }
 
+    Result<WhileStmt *, Error> Parser::parseWhileStmt() // 由 parseStatement调用, 当前token为 while
+    {
+        StateProtector p(this, {State::ParsingWhile});
+
+        SourceLocation location = makeSourceLocation(consumeToken()); // consume `while`
+
+        Expr *cond = nullptr;
+        if (match(TokenType::LeftParen))
+        {
+            const Token &lpToken = prevToken();
+            SET_STOP_AT(TokenType::RightParen, TokenType::LeftBrace);
+
+            auto result = parseExpression();
+            if (!result)
+            {
+                return std::unexpected(result.error());
+            }
+
+            if (!match(TokenType::RightParen))
+            {
+                delete *result;
+                return std::unexpected(Error(ErrorType::SyntaxError,
+                    "unclosed parenthese in while condition",
+                    "insert ')'",
+                    makeSourceLocation(lpToken)));
+            }
+            cond = *result;
+        }
+        else
+        {
+            SET_STOP_AT(TokenType::LeftBrace);
+            auto result = parseExpression();
+            if (!result)
+            {
+                return std::unexpected(result.error());
+            }
+            cond = *result;
+        }
+
+        if (currentToken().type != TokenType::LeftBrace)
+        {
+            delete cond;
+            return std::unexpected(
+                makeUnexpectTokenError("while stmt", "left brace '{'", currentToken()));
+        }
+
+        auto result = parseBlockStmt();
+        if (!result)
+        {
+            delete cond;
+            return std::unexpected(result.error());
+        }
+        BlockStmt *body = *result;
+
+        WhileStmt *whileStmt = new WhileStmt(cond, body, location);
+        return whileStmt;
+    }
+
     Result<Stmt *, Error> Parser::parseStatement()
     {
-        state = State::Standby;
+        StateProtector p(this, {State::Standby});
+
         if (currentToken().type == TokenType::Public)
         {
             consumeToken(); // consume `public`
@@ -247,20 +306,38 @@ namespace Fig
             {
                 return parseVarDecl(true);
             }
+            else
+            {
+                return std::unexpected(
+                    makeUnexpectTokenError("public", "var/const/func/struct", currentToken()));
+            }
         }
+
+        if (currentToken().type == TokenType::LeftBrace)
+        {
+            return parseBlockStmt();
+        }
+
         if (currentToken().type == TokenType::Variable)
         {
             return parseVarDecl(false);
         }
+
         if (currentToken().type == TokenType::If)
         {
             return parseIfStmt();
         }
 
+        if (currentToken().type == TokenType::While)
+        {
+            return parseWhileStmt();
+        }
+
         if (isEOF)
         {
             return nullptr;
         }
+        
         const auto &expr_result = parseExpression();
         if (!expr_result)
         {
diff --git a/src/Sema/Analyzer.cpp b/src/Sema/Analyzer.cpp
index 724ccf1..c39b9e0 100644
--- a/src/Sema/Analyzer.cpp
+++ b/src/Sema/Analyzer.cpp
@@ -11,7 +11,8 @@ namespace Fig
 {
     Result<void, Error> Analyzer::analyzeVarDecl(VarDecl *stmt)
     {
-        if (env.Resolve(stmt->name) != std::nullopt)
+        auto sym = env.Resolve(stmt->name);
+        if (sym != std::nullopt && sym->depth == env.GetDepth())
         {
             return std::unexpected(Error(ErrorType::RedeclarationError,
                 std::format("variable `{}` has already defined in this scope", stmt->name),
@@ -50,7 +51,7 @@ namespace Fig
                 "none",
                 makeSourceLocation(stmt->initExpr)));
         }
-        env.Define(stmt->name, declaredType, stmt->isPublic, false);
+        stmt->localId = env.Define(stmt->name, declaredType, stmt->isPublic, false);
         return {};
     }
 
@@ -63,12 +64,11 @@ namespace Fig
         }
         if (stmt->cond->resolvedType != TypeTag::Any && stmt->cond->resolvedType != TypeTag::Bool)
         {
-            return std::unexpected(Error(
-                ErrorType::TypeError,
-                std::format("if condition must be boolean, got `{}`", magic_enum::enum_name(stmt->cond->resolvedType)),
+            return std::unexpected(Error(ErrorType::TypeError,
+                std::format("if condition must be boolean, got `{}`",
+                    magic_enum::enum_name(stmt->cond->resolvedType)),
                 "ensure condition is boolean",
-                makeSourceLocation(stmt->cond)
-            ));
+                makeSourceLocation(stmt->cond)));
         }
         auto consequentRes = analyzeStmt(stmt->consequent);
         if (!consequentRes)
@@ -106,6 +106,31 @@ namespace Fig
         return {};
     }
 
+    Result<void, Error> Analyzer::analyzeWhileStmt(WhileStmt *stmt)
+    {
+        auto condRes = analyzeExpr(stmt->cond);
+        if (!condRes)
+        {
+            return condRes;
+        }
+
+        if (stmt->cond->resolvedType != TypeTag::Any && stmt->cond->resolvedType != TypeTag::Bool)
+        {
+            return std::unexpected(Error(ErrorType::TypeError,
+                std::format("while condition must be boolean, got `{}`",
+                    magic_enum::enum_name(stmt->cond->resolvedType)),
+                "ensure condition is boolean",
+                makeSourceLocation(stmt->cond)));
+        }
+
+        auto bodyRes = analyzeStmt(stmt->body);
+        if (!bodyRes)
+        {
+            return bodyRes;
+        }
+        return {};
+    }
+
     Result<void, Error> Analyzer::analyzeIdentiExpr(IdentiExpr *expr)
     {
         auto sym = env.Resolve(expr->name);
@@ -117,8 +142,11 @@ namespace Fig
                 makeSourceLocation(expr)));
         }
         // TODO: 引入 Module 跨文件 import，检查 isPublic
-        expr->resolvedType = sym->type;
+        expr->localId = sym->localId;
+
+        expr->resolvedType  = sym->type;
         expr->resolvedDepth = sym->depth;
+        expr->isGlobal = (sym->depth == 0);
 
         return {};
     }
@@ -138,7 +166,7 @@ namespace Fig
 
         switch (expr->op)
         {
-            // 1. 算术族 (+, -, *, /, **)
+            // 算术族 (+, -, *, /, **)
             case BinaryOperator::Add:
                 if (lType == TypeTag::String && rType == TypeTag::String)
                 {
@@ -172,7 +200,7 @@ namespace Fig
                 }
                 break;
 
-            // 2. 整数特化族 (%, &, |, ^, <<, >>)
+            // 整数特化族 (%, &, |, ^, <<, >>)
             case BinaryOperator::Modulo:
             case BinaryOperator::BitAnd:
             case BinaryOperator::BitOr:
@@ -196,8 +224,7 @@ namespace Fig
                 }
                 break;
 
-
-            // 3. 比较族 (==, !=, <, >, <=, >=)
+            // 比较族 (==, !=, <, >, <=, >=)
 
             case BinaryOperator::Equal:
             case BinaryOperator::NotEqual:
@@ -206,7 +233,8 @@ namespace Fig
             case BinaryOperator::LessEqual:
             case BinaryOperator::GreaterEqual:
             case BinaryOperator::Is:
-                if (lType != TypeTag::Any && rType != TypeTag::Any && lType != rType) // lType == rType放行
+                if (lType != TypeTag::Any && rType != TypeTag::Any
+                    && lType != rType) // lType == rType放行
                 {
                     if (!((lType == TypeTag::Int && rType == TypeTag::Double)
                             || (lType == TypeTag::Double && rType == TypeTag::Int)))
@@ -217,7 +245,7 @@ namespace Fig
                             makeSourceLocation(expr)));
                     }
                 }
-                
+
                 // TODO: 支持Struct后进行检查，右操作数是 Struct才合理
                 // 如 1.2 is Int --> false
                 // 1 is Int --> true
@@ -225,8 +253,7 @@ namespace Fig
                 expr->resolvedType = TypeTag::Bool;
                 break;
 
-
-            // 4. 逻辑族 (&&, ||)
+            // 逻辑族 (&&, ||)
             case BinaryOperator::LogicalAnd:
             case BinaryOperator::LogicalOr:
                 if (lType == TypeTag::Bool && rType == TypeTag::Bool)
@@ -246,8 +273,7 @@ namespace Fig
                 }
                 break;
 
-
-            // 5. 纯赋值与复合赋值族 (=, +=, -=, ...)
+            // 纯赋值与复合赋值族 (=, +=, -=, ...)
             case BinaryOperator::Assign:
             case BinaryOperator::AddAssign:
             case BinaryOperator::SubAssign:
@@ -258,12 +284,11 @@ namespace Fig
                 // 左侧必须是合法的 L-Value
                 if (!isValidLvalue(expr->left))
                 {
-                    return std::unexpected(
-                        Error(ErrorType::NotAnLvalue,
-                            "invalid assignment target",
-                            "left side must be a variable, property, or indexable target",
-                            makeSourceLocation(expr->left) // 错误精准定位到左侧节点
-                            ));
+                    return std::unexpected(Error(ErrorType::NotAnLvalue,
+                        "invalid assignment target",
+                        "left side must be a variable, property, or indexable target",
+                        makeSourceLocation(expr->left) // 错误精准定位到左侧节点
+                        ));
                 }
 
                 // 类型匹配拦截 (纯赋值)
@@ -283,8 +308,7 @@ namespace Fig
                 expr->resolvedType = lType;
                 break;
 
-
-            // 6. 成员访问 (.)
+            // 成员访问 (.)
             case BinaryOperator::MemberAccess:
                 if (lType != TypeTag::Struct && lType != TypeTag::Any)
                 {
@@ -293,6 +317,15 @@ namespace Fig
                         "check if the left side evaluates to an object",
                         makeSourceLocation(expr->left)));
                 }
+                if (expr->right->type != AstType::IdentiExpr)
+                {
+                    return std::unexpected(Error(
+                        ErrorType::SyntaxError,
+                        std::format("expect field name after member access '.', got {}", expr->right->toString()),
+                        "none",
+                        makeSourceLocation(expr->right)
+                    ));
+                }
                 expr->resolvedType = TypeTag::Any;
                 break;
 
@@ -335,14 +368,18 @@ namespace Fig
             case AstType::IfStmt: {
                 return analyzeIfStmt(static_cast<IfStmt *>(stmt));
             }
-            
-            // TODO: 其他语句分析
 
-            // default:
-            //     return std::unexpected(Error(ErrorType::TypeError,
-            //         "unsupported statement type in analyzer",
-            //         "internal compiler error",
-            //         makeSourceLocation(stmt)));
+            case AstType::WhileStmt: {
+                return analyzeWhileStmt(static_cast<WhileStmt *>(stmt));
+            }
+
+                // TODO: 其他语句分析
+
+                // default:
+                //     return std::unexpected(Error(ErrorType::TypeError,
+                //         "unsupported statement type in analyzer",
+                //         "internal compiler error",
+                //         makeSourceLocation(stmt)));
         }
         return {};
     }
@@ -356,17 +393,13 @@ namespace Fig
         {
             case AstType::LiteralExpr: {
                 auto *lit = static_cast<LiteralExpr *>(expr);
-                switch(lit->token.type)
+                switch (lit->token.type)
                 {
                     case TokenType::LiteralTrue:
-                    case TokenType::LiteralFalse:
-                        lit->resolvedType = TypeTag::Bool;
-                        break;
-                    
-                    case TokenType::LiteralNull:
-                        lit->resolvedType = TypeTag::Null;
-                        break;
-                    
+                    case TokenType::LiteralFalse: lit->resolvedType = TypeTag::Bool; break;
+
+                    case TokenType::LiteralNull: lit->resolvedType = TypeTag::Null; break;
+
                     case TokenType::LiteralNumber: {
                         const String &lexeme = manager.GetSub(lit->token.index, lit->token.length);
                         if (lexeme.contains(U'.') || lexeme.contains(U'e'))
@@ -385,9 +418,10 @@ namespace Fig
                         break;
                     }
 
-                    default:
+                    default: {
                         lit->resolvedType = TypeTag::Any;
                         break;
+                    }
                 }
                 return {};
             }
diff --git a/src/Sema/Analyzer.hpp b/src/Sema/Analyzer.hpp
index 3e99999..3aa2d66 100644
--- a/src/Sema/Analyzer.hpp
+++ b/src/Sema/Analyzer.hpp
@@ -56,6 +56,7 @@ namespace Fig
 
         Result<void, Error> analyzeVarDecl(VarDecl *);
         Result<void, Error> analyzeIfStmt(IfStmt *);
+        Result<void, Error> analyzeWhileStmt(WhileStmt *);
         
         Result<void, Error> analyzeIdentiExpr(IdentiExpr *);
         Result<void, Error> analyzeInfixExpr(InfixExpr *);
diff --git a/src/Sema/AnalyzerTest.cpp b/src/Sema/AnalyzerTest.cpp
index 33857d7..dc11b9b 100644
--- a/src/Sema/AnalyzerTest.cpp
+++ b/src/Sema/AnalyzerTest.cpp
@@ -24,10 +24,10 @@ int main()
         return 1;
     }
 
-    Lexer lexer(manager.GetSource(), fileName);
+    Lexer  lexer(manager.GetSource(), fileName);
     Parser parser(lexer, manager, fileName);
 
-    const auto &result = parser.Parse();
+    auto result = parser.Parse();
     if (!result)
     {
         ReportError(result.error(), manager);
diff --git a/src/Sema/Environment.hpp b/src/Sema/Environment.hpp
index 7a6f7e6..077100e 100644
--- a/src/Sema/Environment.hpp
+++ b/src/Sema/Environment.hpp
@@ -7,15 +7,15 @@
 
 #pragma once
 
-#include <Sema/Type.hpp>
 #include <Deps/Deps.hpp>
 #include <Error/Error.hpp>
+#include <Sema/Type.hpp>
 
+#include <cassert>
 #include <optional>
 
 namespace Fig
 {
-
     // 记录在 Analyzer 中的符号元数据
     struct Symbol
     {
@@ -24,41 +24,108 @@ namespace Fig
         bool    isPublic;
         int     depth;      // 词法作用域深度
         bool    isConstant; // 是否是 const 声明的不可变常量 (用于报错: 尝试修改常量)
+
+        int localId = -1; // Analyzer 虚拟槽位分配
+    };
+
+    // 作用域回档水位线
+    struct ScopeWatermark
+    {
+        std::size_t symbolCount;
+        int         savedLocalId;
+    };
+
+    // 语义分析函数上下文 (隔离局部变量 ID 空间)
+    struct SemaFuncState
+    {
+        SemaFuncState           *enclosing    = nullptr;
+        int                      currentDepth = 0;
+        int                      nextLocalId  = 0;
+        DynArray<ScopeWatermark> scopeStack;
     };
 
     class Environment
     {
     private:
         DynArray<Symbol> symbols;
-        int              currentDepth = 0;
+        SemaFuncState   *current = nullptr;
 
     public:
+        Environment()
+        {
+            current = new SemaFuncState();
+        }
+
+        ~Environment()
+        {
+            while (current)
+            {
+                SemaFuncState *prev = current->enclosing;
+                delete current;
+                current = prev;
+            }
+        }
+
+        // 函数边界控
+
+        void EnterFunction()
+        {
+            SemaFuncState *newState = new SemaFuncState();
+            newState->enclosing     = current;
+            current                 = newState;
+        }
+
+        void LeaveFunction()
+        {
+            assert(current && "Environment: Unmatched LeaveFunction");
+            SemaFuncState *oldState = current;
+            current                 = oldState->enclosing;
+            delete oldState;
+        }
+
+        // 词法作用域控制
+
         void EnterScope()
         {
-            currentDepth++;
+            current->currentDepth++;
+            current->scopeStack.push_back({symbols.size(), current->nextLocalId});
         }
+
         void LeaveScope()
         {
-            while (!symbols.empty() && symbols.back().depth > currentDepth)
+            assert(current->currentDepth > 0 && "Environment: Unmatched LeaveScope");
+            current->currentDepth--;
+
+            assert(!current->scopeStack.empty());
+            ScopeWatermark archive = current->scopeStack.back();
+            current->scopeStack.pop_back();
+
+            // 物理截断符号表，回滚槽位发号器以复用物理寄存器
+            while (symbols.size() > archive.symbolCount)
             {
                 symbols.pop_back();
             }
-            currentDepth--;
+            current->nextLocalId = archive.savedLocalId;
         }
 
-        // 注册符号, 调用前确保无重复 (内部assert)
-        void Define(const String &name, TypeTag type, bool isPublic, bool isConst)
+        // 符号操作
+
+        // 注册符号, 返回分配的 localId。调用前内部执行同级作用域重定义断言
+        int Define(const String &name, TypeTag type, bool isPublic, bool isConst)
         {
             for (auto it = symbols.rbegin(); it != symbols.rend(); ++it)
             {
-                if (it->depth < currentDepth)
+                if (it->depth < current->currentDepth)
                     break;
                 if (it->name == name)
                 {
                     assert(false && "Environment.Define: redefinition");
                 }
             }
-            symbols.push_back({name, type, isPublic, currentDepth, isConst});
+
+            int allocatedId = current->nextLocalId++;
+            symbols.push_back({name, type, isPublic, current->currentDepth, isConst, allocatedId});
+            return allocatedId;
         }
 
         // 解析符号。找不到返回 nullopt
@@ -74,7 +141,7 @@ namespace Fig
 
         int GetDepth() const
         {
-            return currentDepth;
+            return current->currentDepth;
         }
     };
 } // namespace Fig
\ No newline at end of file
diff --git a/src/main.cpp b/src/main.cpp
index 4ddf0f3..015a552 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3,13 +3,15 @@
 #include <Deps/Deps.hpp>
 #include <Lexer/Lexer.hpp>
 #include <Parser/Parser.hpp>
-#include <SourceManager/SourceManager.hpp>
 #include <Sema/Analyzer.hpp>
+#include <SourceManager/SourceManager.hpp>
 #include <VM/VM.hpp>
 
+
+#include <chrono>
 #include <iostream>
 #include <print>
-#include <chrono>
+
 
 int main()
 {
@@ -38,7 +40,7 @@ int main()
     }
     Program *program = *program_result;
 
-    Analyzer analyzer(manager);
+    Analyzer    analyzer(manager);
     const auto &analyzeResult = analyzer.Analyze(program);
     if (!analyzeResult)
     {
@@ -47,7 +49,6 @@ int main()
     }
     std::cout << "analyzer: Program OK, PASSED\n";
 
-
     Compiler    compiler(fileName, manager);
     const auto &proto_result = compiler.Compile(program);
     if (!proto_result)
@@ -67,10 +68,10 @@ int main()
     DumpCode(proto->code);
 
     std::cout << "\nMax Stack Size: " << (int) proto->maxStack << std::endl;
-    
+
     VM vm;
 
-    const auto &result_ = vm.Execute(proto);
+    auto result_ = vm.Execute(proto);
     if (!result_)
     {
         ReportError(result_.error(), manager);
diff --git a/xmake.lua b/xmake.lua
index 248bafc..b9c36a6 100644
--- a/xmake.lua
+++ b/xmake.lua
@@ -101,7 +101,7 @@ target("LSP")
 
     add_files("src/Sema/Analyzer.cpp")
 
-    add_files("src/LSP/FigLSPServer.cpp")
+    add_files("src/LSP/LSPServer.cpp")
 
     set_filename("Fig-LSP")