[TypeDeclaration] Closure Param Types from Iterator Source

[peterfox]

Changes

• Adds a new rule AddClosureParamTypeFromIterableMethodCallRector
• Adds new methods to TypeUnwrapper
  • unwrapFirstCallableTypeFromUnionType(Type $type): ?Type
  • isIterableTypeValue(string $className, Type $type): bool
  • isIterableTypeKey(string $className, Type $type): bool
• Adds tests for the rule

Why

This rule should make it easy to type hint closures based on PHPStan's generics.

class Fixture
{
    /**
     * @param Collection<int, string> $collection
     */
    public function run(Collection $collection)
    {
-        return $collection->map(function ($item, $key) {
+        return $collection->map(function (string $item, int $key) {
            return $item . $key;
        });
    }
}

Notes

I'd like to bring this to functions as well, but that will take a bit more effort to establish the iterator source. I'd be open to recommendations of how to put some code from this rule into more reusable classes.

[peterfox]

Thank you for the review @samsonasik

[TomasVotruba]

Thank you @peterfox 🙏