[CodeQuality] Add RemoveReturnFromVoidMethodMockCallbackRector

[TomasVotruba]

Adds VoidMockCallbackRector.

When a mocked method returns void, its callback closure has no reason to return true; (or any value). This rule resolves the mocked method via reflection, and when it is void, drops the value return and types the closure as : void.

Covers both ->willReturnCallback(...) and ->with($this->callback(...)).

willReturnCallback()

 $this->createMock(SomeEntityManager::class)
     ->method('persist')
-    ->willReturnCallback(function ($entity) {
+    ->willReturnCallback(function ($entity): void {
         echo $entity;
-
-        return true;
     });

with($this->callback()), mock assigned in setUp()

 $this->entityManager
     ->method('persist')
-    ->with($this->callback(function ($entity): bool {
+    ->with($this->callback(function ($entity): void {
         $this->assertInstanceOf(\stdClass::class, $entity);
-
-        return true;
     }));

persist() is void, so the callback becomes void too.

Skipped

• non-void mocked methods (return value kept)
• closures already typed void
• returns of computed/side-effectful expressions (only scalar/const/variable values are dropped)