Fix subtracting types from union template types

[rvanvelzen]

Fix phpstan/phpstan#9939

[phpstan-bot]

You've opened the pull request against the latest branch 1.11.x. If your code is relevant on 1.10.x and you want it to be released sooner, please rebase your pull request and change its target to 1.10.x.

[ondrejmirtes]

FYI @rvanvelzen I described an issue here phpstan/phpstan#9925 (reply in thread), I think it's up your alley to fix it :)

New_ has special behaviour in MutatingScope::exactInstantiation that looks at class-level @template and uses them for constructor. Maybe we would benefit from moving it into ParametersAcceptorSelector, maybe that would help us in part to solve that issue.

If you decide to look at it that would be great!

[ondrejmirtes]

This needs to be put in PHP_VERSION_ID if.

[ondrejmirtes]

Also it's better to put in some random place in the middle, because at the end it's more likely to have conflict when merging into 1.11.x

[ondrejmirtes]

This needs // lint >= 8.1

[ondrejmirtes]

Thank you!

[thg2k]

Maybe a simplified test case instead of that bloated one? This is also PHP-version independent

<?php declare(strict_types = 1);

/**
 * @template T of string|array<string>
 */
class C {
  /**
   * @param T $a
   */
  public function foo($a): string {
    if (is_array($a)) {
      return "";
    }
    \PHPStan\Testing\assertType('T of string (class C, argument)', $a);
    return (string) $a;
  }
}

https://phpstan.org/r/bc6b8adf-a25e-4960-8f43-eca8399cf509