[Php80] Skip mixed and untyped calls in TernaryToNullsafeCoalesceRector

TypeCombinator::containsNull() is false for MixedType, so a call returning mixed (or declaring no return type) was rewritten to "?->... ?? $fallback", and a null result started falling through to the fallback.

Assisted-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: roxblnfk

rules-tests/Php80/Rector/Ternary/TernaryToNullsafeCoalesceRector/Fixture/skip_mixed_return.php.inc

@@ -0,0 +1,23 @@
+<?php
+
+namespace Rector\Tests\Php80\Rector\Ternary\TernaryToNullsafeCoalesceRector\Fixture;
+
+use Rector\Tests\Php80\Rector\Ternary\TernaryToNullsafeCoalesceRector\Source\SomeObject;
+
+final class SkipMixedReturn
+{
+    public function run(?SomeObject $someObject): mixed
+    {
+        return null !== $someObject ? $someObject->findMixed() : '';
+    }
+
+    public function runUntyped(?SomeObject $someObject): mixed
+    {
+        return null !== $someObject ? $someObject->findUntyped() : '';
+    }
+
+    public function runUntypedProperty(?SomeObject $someObject): mixed
+    {
+        return null !== $someObject ? $someObject->untypedName : '';
+    }
+}

rules-tests/Php80/Rector/Ternary/TernaryToNullsafeCoalesceRector/Source/SomeObject.php

@@ -8,6 +8,8 @@ final class SomeObject
 {
     public string $name = 'name';
 
+    public $untypedName = 'name';
+
     public function getName(): string
     {
         return $this->name;
@@ -17,4 +19,14 @@ public function findName(): ?string
     {
         return $this->name;
     }
+
+    public function findMixed(): mixed
+    {
+        return $this->name;
+    }
+
+    public function findUntyped()
+    {
+        return $this->name;
+    }
 }

rules/Php80/Rector/Ternary/TernaryToNullsafeCoalesceRector.php

@@ -16,7 +16,6 @@
 use PhpParser\Node\Expr\StaticPropertyFetch;
 use PhpParser\Node\Expr\Ternary;
 use PhpParser\Node\Expr\Variable;
-use PHPStan\Type\TypeCombinator;
 use Rector\PhpParser\Node\Value\ValueResolver;
 use Rector\Rector\AbstractRector;
 use Rector\ValueObject\PhpVersionFeature;
@@ -185,13 +184,14 @@ private function isPureExpr(Expr $expr): bool
     /**
      * Guards the "?? $fallback" rewrite.
      *
-     * The ternary and the coalesce only agree while the call itself cannot return null:
+     * The ternary and the coalesce only agree while the call itself cannot return null,
+     * so "mixed" and untyped calls are skipped too:
      *
      *     null !== $a ? $a->find() : ''   // $a->find() returning null yields null
      *     $a?->find() ?? ''               // $a->find() returning null yields ''
      */
     private function shouldSkipCoalesceFallback(Expr $callExpr): bool
     {
-        return TypeCombinator::containsNull($this->getType($callExpr));
+        return ! $this->getType($callExpr)->isNull()->no();
     }
 }