fix(frontend): 修复部分实现

src/irgen/IRGenDecl.cpp

@@ -6,27 +6,22 @@
 #include "ir/IR.h"
 
 void IRGenImpl::GenBlock(SysYParser::BlockContext& block) {
-  for (auto* stmt : block.stmt()) {
-    if (stmt && stmt->varDecl()) {
-      const std::string name = stmt->varDecl()->Ident()->getText();
-      auto* slot = builder_.CreateAllocaI32(ir::DefaultContext().NextTemp());
-      locals_[name] = slot;
-    }
-  }
-
   for (auto* stmt : block.stmt()) {
     if (stmt) {
-      GenStmt(*stmt);
+      if (GenStmt(*stmt)) {
+        break;
+      }
     }
   }
 }
 
 void IRGenImpl::GenVarDecl(SysYParser::VarDeclContext& decl) {
   const std::string name = decl.Ident()->getText();
-  auto it = locals_.find(name);
-  if (it == locals_.end()) {
-    throw std::runtime_error("[irgen] 变量栈槽未创建: " + name);
+  if (locals_.find(name) != locals_.end()) {
+    throw std::runtime_error("[irgen] 重复定义变量: " + name);
   }
+  auto* slot = builder_.CreateAllocaI32(ir::DefaultContext().NextTemp());
+  locals_[name] = slot;
 
   ir::Value* init = nullptr;
   if (decl.exp()) {
@@ -34,5 +29,5 @@ void IRGenImpl::GenVarDecl(SysYParser::VarDeclContext& decl) {
   } else {
     init = ir::DefaultContext().GetConstInt(0);
   }
-  builder_.CreateStore(init, it->second);
+  builder_.CreateStore(init, slot);
 }