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Impossible template types not rejeced #2579
Description
Code snippet that reproduces the problem
class A {}
class B {}
class A1 extends A {
public function foo() : void {}
}
class B1 extends B {
public function bar() : void {}
}
/**
* @template T1 of A
* @template T2 of B
* @param T1|T2 $type
* @return T1|T2
*/
function f(object $type) {
return new $type();
}
(f(new A1))->foo(); // should pass
(f(new B1))->bar(); // should pass
(f(new A1))->bar(); // should fail
(f(new B1))->foo(); // should failhttps://phpstan.org/r/a7b835ae-b7a1-4cda-b7ba-3b3f13713fb6
Expected output
See above
Actual output
+---------------------------------------------------------------------+
| Line | test.php |
+---------------------------------------------------------------------+
| 21 | Call to an undefined method A1|B::foo(). |
| 21 | Unable to resolve the template type T2 in call to function f |
| 22 | Call to an undefined method A|B1::bar(). |
| 22 | Unable to resolve the template type T1 in call to function f |
| 24 | Call to an undefined method A1|B::bar(). |
| 24 | Unable to resolve the template type T2 in call to function f |
| 25 | Call to an undefined method A|B1::foo(). |
| 25 | Unable to resolve the template type T1 in call to function f |
+---------------------------------------------------------------------+
Activity
ondrejmirtes commentedon Nov 11, 2019
I confirm - this is a bug and should be easy to fix.
ondrejmirtes commentedon Nov 30, 2019
On the other hand, this is a weird example. To have a successful type resolution, we need to resolve all template types in a function call. When we're passing A1 as the argument, we don't have anything to resolve as T2. So we cannot construct the return type. On line 21, the function according to its signature always returns something as B. So it's not safe to call something that's only on A.
With a simple signature that also describes what the functon does, it behaves as expected: https://phpstan.org/r/02a16855-0d1c-42dd-aa28-8e281c48df81
muglug commentedon Nov 30, 2019
Yes, that describes a lot of the bugs people report with templating.
But here we can reasonably say that an unmatched template should be bound to the
emptytype or similar - that is, a type that disappears in any union.ondrejmirtes commentedon Dec 1, 2019
Unmatched template type is resolved to its bound and not to never.
I think we'd be able to construct method body with the above signature that would break in runtime without Psalm complaining about anything...
The question really is - does
T1|T2mean that the function expects a union of two types, or does it mean that I can pass in either of them. /cc @arnaud-lbphpstan-bot commentedon Mar 9, 2021
@ondrejmirtes PHPStan now reports different result with your code snippet:
Full report
Function f() should return T1 of object but returns mixed.Call to an undefined method A1::bar().Call to an undefined method B1::foo().phpstan-bot commentedon Sep 15, 2021
@ondrejmirtes After the latest commit in dev-master, PHPStan now reports different result with your code snippet:
Full report
Function f() should return T1 of object but returns object.Call to an undefined method A1::bar().Call to an undefined method B1::foo().ZebulanStanphill commentedon Mar 25, 2022
Looks like this is fixed now in PHPStan 1.5.0.