[Php56] Skip AddDefaultValueForUndefinedVariableRector as coalesce le…

…ft (#1238)

* [Php56] Skip FAddDefaultValueForUndefinedVariableRector in coalesce

* Fixed 🎉

rules-tests/Php56/Rector/FunctionLike/AddDefaultValueForUndefinedVariableRector/Fixture/skip_coalesce.php.inc

@@ -0,0 +1,15 @@
+<?php
+
+namespace Rector\Tests\Php56\Rector\FunctionLike\AddDefaultValueForUndefinedVariableRector\Fixture;
+
+class SkipCoalesce
+{
+    public function run()
+    {
+        if (rand(0,1)) {
+            $value = 'value';
+        }
+
+        return $value ?? 'test';
+    }
+}

rules/Php56/NodeAnalyzer/UndefinedVariableResolver.php

@@ -9,6 +9,7 @@
 use PhpParser\Node\Expr\ArrowFunction;
 use PhpParser\Node\Expr\Assign;
 use PhpParser\Node\Expr\AssignRef;
+use PhpParser\Node\Expr\BinaryOp\Coalesce;
 use PhpParser\Node\Expr\Cast\Unset_ as UnsetCast;
 use PhpParser\Node\Expr\Closure;
 use PhpParser\Node\Expr\Isset_;
@@ -114,6 +115,11 @@ private function issetOrUnsetParent(Node $parentNode): bool
         return in_array($parentNode::class, [Unset_::class, UnsetCast::class, Isset_::class], true);
     }
 
+    private function isAsCoalesceLeft(Node $parentNode, Variable $variable): bool
+    {
+        return $parentNode instanceof Coalesce && $parentNode->left === $variable;
+    }
+
     private function isAssignOrStaticVariableParent(Node $parentNode): bool
     {
         if (in_array($parentNode::class, [Assign::class, AssignRef::class], true)) {
@@ -142,6 +148,10 @@ private function shouldSkipVariable(Variable $variable): bool
             return true;
         }
 
+        if ($this->isAsCoalesceLeft($parentNode, $variable)) {
+            return true;
+        }
+
         // list() = | [$values] = defines variables as null
         if ($this->isListAssign($parentNode)) {
             return true;