From 39bec62e15e37e0fe173fff4982840dc37c6f68f Mon Sep 17 00:00:00 2001
From: tianfenghan <rango@swoole.com>
Date: Tue, 14 Jul 2026 12:38:24 +0800
Subject: [PATCH] fix(compiler): infer concat expressions as strings

---
 phpunit/src/SsaAnalysisTest.php | 9 +++++++++
 src/CompilerBase.php            | 3 +++
 2 files changed, 12 insertions(+)

diff --git a/phpunit/src/SsaAnalysisTest.php b/phpunit/src/SsaAnalysisTest.php
index 89396f87..e0739242 100644
--- a/phpunit/src/SsaAnalysisTest.php
+++ b/phpunit/src/SsaAnalysisTest.php
@@ -1263,6 +1263,15 @@ class SsaAnalysisTest extends TestCase
         }
     }
 
+    public function testDetectTypeOfConcatExpressions(): void
+    {
+        $concat = new Expr\BinaryOp\Concat(new Scalar\LNumber(1), new Scalar\String_(''));
+        $concatAssign = new Expr\AssignOp\Concat(new Expr\Variable('value'), new Scalar\LNumber(2));
+
+        $this->assertSame(Type::STR, $this->invoke('detectTypeOfExpr', $concat));
+        $this->assertSame(Type::STR, $this->invoke('detectTypeOfExpr', $concatAssign));
+    }
+
     public function testDetectSsaDefTypeNull(): void
     {
         $ssaVar = new SsaVar(1, 'x');
diff --git a/src/CompilerBase.php b/src/CompilerBase.php
index 2d8f90dd..36da7790 100644
--- a/src/CompilerBase.php
+++ b/src/CompilerBase.php
@@ -2299,6 +2299,9 @@ class CompilerBase implements PropertyAccessContext
             case 'Expr_Array':
             case 'Expr_Cast_Array':
                 return Type::ARRAY;
+            case 'Expr_BinaryOp_Concat':
+            case 'Expr_AssignOp_Concat':
+                return Type::STR;
             case 'Expr_BinaryOp_Plus':
             case 'Expr_BinaryOp_Minus':
             case 'Expr_BinaryOp_Mul':