refactor(php): 优化变量赋值表达式解析逻辑

- 提取变量类型获取逻辑到局部变量以提高可读性
- 移除冗余的类型检查转换逻辑
- 简化赋值操作中的类型处理流程
- 保持原有的类型推断功能不变
- 改进代码结构以增强维护性

src/Php/Parser/AssignOpTrait.php

@@ -236,7 +236,8 @@ trait AssignOpTrait
                     $finalVarType = $this->isNativeType($type) ? $this->getNativeType($type) : $type;
                     $this->addLocalVar($var, $finalVarType);
                 } else {
-                    $this->checkVarAssignExpr($left, $this->getVarType($var), $type);
+                    $finalVarType = $this->getVarType($var);
+                    $this->checkVarAssignExpr($left, $finalVarType, $type);
                 }
             }
         } elseif ($this->isPropertyFetch($left) and !$left->getAttribute('nativeProperty')) {
@@ -252,17 +253,6 @@ trait AssignOpTrait
             return $this->parseAssignArrayDim($left, $right);
         }
 
-        // When the RHS is untyped (TYPE_VAR) but the LHS variable already has a known
-        // native type, use the LHS type for the conversion so that e.g.
-        //   php::Int i;  ...  i = n;  (n is php::Var)
-        // becomes  i = php::toInt(n);
-        if ($finalVarType === self::TYPE_VAR && $this->hasVar($var)) {
-            $varType = $this->getVarType($var);
-            if ($varType !== self::TYPE_VAR) {
-                $finalVarType = $varType;
-            }
-        }
-
         $rightExpr = $this->parseAssignRightExpr($right);
         $leftExprType = $this->detectTypeOfExpr($left);
         $rightExprType = $this->detectTypeOfExpr($right);