[CodeQuality] Skip multiple lines on JoinStringConcatRector (#6404)

rules-tests/CodeQuality/Rector/Concat/JoinStringConcatRector/Fixture/skip_multiple_lines.php.inc

@@ -0,0 +1,14 @@
+<?php
+
+namespace Rector\Tests\CodeQuality\Rector\Concat\JoinStringConcatRector\Fixture;
+
+class SkipMultiplelines
+{
+    public function run()
+    {
+        return 'a' .
+            'b' .
+            'c' .
+            'd';
+    }
+}

rules/CodeQuality/Rector/Concat/JoinStringConcatRector.php

@@ -81,6 +81,13 @@ public function refactor(Node $node): ?Node
             return null;
         }
 
+        $leftStartLine = $node->left->getStartLine();
+        $rightStartLine = $node->right->getStartLine();
+
+        if ($leftStartLine > 0 && $rightStartLine > 0 && $rightStartLine > $leftStartLine) {
+            return null;
+        }
+
         return $this->joinConcatIfStrings($node->left, $node->right);
     }