Incorrect behavior of DowngradeParameterTypeWideningRector

[leoloso]

Bug Report

Subject	Details
Rector version	last dev-master
Installed as	composer dependency

Minimal PHP Code Causing Issue

See https://getrector.org/demo/1b8ee6a0-7d50-4fae-8e15-f19d19591fc5

<?php
trait StreamDecoratorTrait
{
    protected function createStream()
    {
        // ...
    }
}

class MultipartStream
{
    use StreamDecoratorTrait;

    protected function createStream(array $elements)
    {
        // ...
    }
}

Responsible rules

• DowngradeParameterTypeWideningRector

Expected Behavior

The rule is currently doing this:

class MultipartStream
{
    use StreamDecoratorTrait;

-    protected function createStream(array $elements)
+    protected function createStream($elements)
    {
        // ...
    }
}

Instead, it should do nothing:

class MultipartStream
{
    use StreamDecoratorTrait;

    protected function createStream(array $elements)
    {
        // ...
    }
}

DowngradeParameterTypeWideningRector should not remove the type array of the param $elements, because the different method comes from a trait. But only parent classes and interfaces should be considered, not traits.

Debugging DowngradeParameterTypeWideningRector, I found out this:

// Remove the types in:
// - all ancestors + their descendant classes
// - all implemented interfaces + their implementing classes
$parameterTypesByParentClassLikes = $this->resolveParameterTypesByClassLike(
    $classReflection,
    $methodName,
    $position
);
var_dump($parameterTypesByParentClassLikes);

Prints:

array(2) {
  ["GuzzleHttp\Psr7\MultipartStream"]=>
  object(PHPStan\Type\ArrayType)#27706 (2) {
    ["keyType":"PHPStan\Type\ArrayType":private]=>
    object(PHPStan\Type\MixedType)#27715 (2) {
      ["isExplicitMixed":"PHPStan\Type\MixedType":private]=>
      bool(false)
      ["subtractedType":"PHPStan\Type\MixedType":private]=>
      NULL
    }
    ["itemType":"PHPStan\Type\ArrayType":private]=>
    object(PHPStan\Type\MixedType)#27701 (2) {
      ["isExplicitMixed":"PHPStan\Type\MixedType":private]=>
      bool(false)
      ["subtractedType":"PHPStan\Type\MixedType":private]=>
      NULL
    }
  }
  ["GuzzleHttp\Psr7\StreamDecoratorTrait"]=>
  object(PHPStan\Type\MixedType)#27710 (2) {
    ["isExplicitMixed":"PHPStan\Type\MixedType":private]=>
    bool(false)
    ["subtractedType":"PHPStan\Type\MixedType":private]=>
    NULL
  }
}

Hence, StreamDecoratorTrait is also being picked by resolveParameterTypesByClassLike, that's the problem.