fix(parser): 修复变量类型推断问题

- 当右侧表达式为无类型但左侧变量已有已知原生类型时，
  使用左侧类型进行转换以确保类型安全
- 在赋值操作中添加类型检查逻辑，避免类型丢失问题
- 更新 fibo 和 fibo_r 函数参数类型声明为 int
- 添加 issetor 性能测试用例以验证类型推断优化效果

examples/bench.php

@@ -179,11 +179,11 @@ function ary3($n) {
 
 /****/
 
-function fibo_r($n){
+function fibo_r(int $n){
     return(($n < 2) ? 1 : fibo_r($n - 2) + fibo_r($n - 1));
 }
 
-function fibo($n) {
+function fibo(int $n) {
   $r = fibo_r($n);
   print "$r\n";
 }

perf/issetor.php

@@ -0,0 +1,15 @@
+<?php
+function issetor(int $n)
+{
+    $val = array(0, 1, 2, 3, 4, 5, 6, 7, 8, 9);
+    for ($i = 0; $i < $n; ++$i) {
+        $x = $val ?: null;
+    }
+}
+
+function main()
+{
+    $s = microtime( true);
+    issetor(1000_0000);
+    echo microtime( true) - $s . "\n";
+}

src/Php/Parser/AssignOpTrait.php

@@ -252,6 +252,17 @@ 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);