style(ir): 纠正代码位置

src/sem/Sema.cpp

@@ -7,43 +7,47 @@
 
 namespace {
 
-void CheckExpr(SysYParser::ExpContext& exp, const SymbolTable& table);
+void CheckExpr(SysYParser::ExpContext& exp, const SymbolTable& table,
+               SemanticContext& sema);
 
 void CheckPrimary(SysYParser::PrimaryContext& primary,
-                  const SymbolTable& table) {
+                  const SymbolTable& table, SemanticContext& sema) {
   if (primary.Number()) {
     return;
   }
 
   if (primary.Ident()) {
     const std::string name = primary.Ident()->getText();
-    if (!table.Contains(name)) {
+    auto* decl = table.Lookup(name);
+    if (!decl) {
       throw std::runtime_error("[sema] 使用了未定义的变量: " + name);
     }
+    sema.BindVarUse(&primary, decl);
     return;
   }
 
   if (primary.exp()) {
-    CheckExpr(*primary.exp(), table);
+    CheckExpr(*primary.exp(), table, sema);
     return;
   }
 
   throw std::runtime_error("[sema] 暂不支持的 primary 形式");
 }
 
-void CheckExpr(SysYParser::ExpContext& exp, const SymbolTable& table) {
+void CheckExpr(SysYParser::ExpContext& exp, const SymbolTable& table,
+               SemanticContext& sema) {
   if (!exp.addExp()) {
     throw std::runtime_error("[sema] 非法表达式");
   }
   const auto& terms = exp.addExp()->primary();
   for (auto* term : terms) {
-    CheckPrimary(*term, table);
+    CheckPrimary(*term, table, sema);
   }
 }
 
 }  // namespace
 
-void RunSema(SysYParser::CompUnitContext& comp_unit) {
+SemanticContext RunSema(SysYParser::CompUnitContext& comp_unit) {
   auto* func = comp_unit.funcDef();
   if (!func || !func->block()) {
     throw std::runtime_error("[sema] 缺少 main 函数定义");
@@ -53,6 +57,7 @@ void RunSema(SysYParser::CompUnitContext& comp_unit) {
   }
 
   SymbolTable table;
+  SemanticContext sema;
   bool seen_return = false;
 
   const auto& items = func->block()->blockItem();
@@ -74,14 +79,14 @@ void RunSema(SysYParser::CompUnitContext& comp_unit) {
         throw std::runtime_error("[sema] 重复定义变量: " + name);
       }
       if (decl->exp()) {
-        CheckExpr(*decl->exp(), table);
+        CheckExpr(*decl->exp(), table, sema);
       }
-      table.Add(name);
+      table.Add(name, decl);
       continue;
     }
     if (auto* stmt = item->stmt(); stmt && stmt->returnStmt()) {
       auto* ret = stmt->returnStmt();
-      CheckExpr(*ret->exp(), table);
+      CheckExpr(*ret->exp(), table, sema);
       seen_return = true;
       if (i + 1 != items.size()) {
         throw std::runtime_error("[sema] return 必须是 main 函数中的最后一条语句");
@@ -94,4 +99,6 @@ void RunSema(SysYParser::CompUnitContext& comp_unit) {
   if (!seen_return) {
     throw std::runtime_error("[sema] main 函数必须包含 return 语句");
   }
+
+  return sema;
 }

src/sem/Sema.h

@@ -1,9 +1,30 @@
-// 基于语法树的极简语义检查。
+// 基于语法树的极简语义检查与名称绑定。
 #pragma once
 
+#include <unordered_map>
+
 #include "SysYParser.h"
 
+class SemanticContext {
+ public:
+  void BindVarUse(SysYParser::PrimaryContext* use,
+                  SysYParser::VarDeclContext* decl) {
+    var_uses_[use] = decl;
+  }
+
+  SysYParser::VarDeclContext* ResolveVarUse(
+      const SysYParser::PrimaryContext* use) const {
+    auto it = var_uses_.find(use);
+    return it == var_uses_.end() ? nullptr : it->second;
+  }
+
+ private:
+  std::unordered_map<const SysYParser::PrimaryContext*,
+                     SysYParser::VarDeclContext*>
+      var_uses_;
+};
+
 // 目前仅检查：
 // - 变量先声明后使用
 // - 局部变量不允许重复定义
-void RunSema(SysYParser::CompUnitContext& comp_unit);
+SemanticContext RunSema(SysYParser::CompUnitContext& comp_unit);

src/sem/SymbolTable.h

@@ -1,16 +1,24 @@
-// 极简符号表：记录局部变量是否定义。
+// 极简符号表：记录局部变量定义点。
 #pragma once
 
 #include <string>
 #include <unordered_map>
 
+#include "SysYParser.h"
+
 class SymbolTable {
  public:
-  void Add(const std::string& name) { table_[name] = true; }
+  void Add(const std::string& name, SysYParser::VarDeclContext* decl) {
+    table_[name] = decl;
+  }
   bool Contains(const std::string& name) const {
     return table_.find(name) != table_.end();
   }
+  SysYParser::VarDeclContext* Lookup(const std::string& name) const {
+    auto it = table_.find(name);
+    return it == table_.end() ? nullptr : it->second;
+  }
 
  private:
-  std::unordered_map<std::string, bool> table_;
+  std::unordered_map<std::string, SysYParser::VarDeclContext*> table_;
 };