Closure params inappropriately bound

[muglug]

Bug report

So, template upper & lower bounds. They're fun.

Here we have two types of bounds set: an upper bound (the T inside class-string<T>) and a lower bound (the T inside Closure(T):void).

What we care about is the upper bound – the most specific type we can infer in the call to createProxy, in this case A. It's incorrect to union the lower-bounded type and the upper-bounded type together, as they represent wholly different constraints on the value of T.

Code snippet that reproduces the problem

/**
 * @template T as object
 * @param class-string<T> $className
 * @param Closure(T):void $outmaker
 * @return T
 */
function createProxy(
    string $className,
    Closure $outmaker
) : object {
    $t = new $className();
    $outmaker($t);
    return $t;
}

class AParent {}

class A extends AParent {
    public function bar() : void {}
}

createProxy(A::class, function(AParent $o):void {})->bar();

Expected output

No issue

Actual

Call to an undefined method AParent::bar().

https://phpstan.org/r/a0d9b3fd-e762-4022-80b5-51223678a665

[phpstan-bot]

@muglug After the latest commit in dev-master, PHPStan now reports different result with your code snippet:

@@ @@
-24: Call to an undefined method AParent::bar().
+No errors

[ondrejmirtes]

I cheated a bit here (phpstan/phpstan-src@efa6aa6), I need to find the right solution.

[github-actions]

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