Method with this-out cannot apply union to template type of array-key #13374

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1. axlon commented on Aug 9, 2025

   

   axlon

   on Aug 9, 2025

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   It appears that it has nothing to do with part of the union not being a template type; I am able to reproduce the issue with a union of two template types: https://phpstan.org/r/be6cc85e-bd4a-482a-803d-61cb0fd95b12

   My best guess is that the of array-key on the class template type is causing this, because when I remove (line 7) it it does seem to work: https://phpstan.org/r/425539f8-daa0-467c-9330-ac6661a124d0
2. axlon

   changed the title [-]Method with this-out does not support union of template type and normal type[/-] [+]Method with this-out cannot apply union to template type with boundary[/+] on Aug 9, 2025
3. axlon

   changed the title [-]Method with this-out cannot apply union to template type with boundary[/-] [+]Method with this-out cannot apply union to template type of array-key[/+] on Aug 9, 2025
4. VincentLanglet commented on Aug 10, 2025

   

   VincentLanglet

   on Aug 10, 2025

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   array-key is a benevolent union of int and string.
   so int|(int|string) is simplified to (int|string) in your phpdoc which is your template,
   so int|TKey is indeed simplified to TKey.

   You won't get the issue by using int|string instead.
   https://phpstan.org/r/3577d04a-545c-4431-b404-9ee5d00c86d8
5. ondrejmirtes commented on Sep 2, 2025

   

   ondrejmirtes

   on Sep 2, 2025

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   int|TKey shouldn't be normalized. When doing type normalization (https://phpstan.org/developing-extensions/type-system#type-normalization) parts of a union type are consumed by another when $eaterType->isSuperTypeOf($consumedType)->yes().

   But with int and TKey neither type is a super type of each other.
6. VincentLanglet commented on Sep 3, 2025

   

   VincentLanglet

   on Sep 3, 2025

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   Let's say $int is int et $tkey is TKey.

   The call

   $int->isSuperTypeOf($tkey)
   

   is triggering

   $tkey->isSubTypeOf($int)
   

   since TKey is a CompoundType because it's an UnionType(benevolent one)

   The implementation is

   public function isSubTypeOf(Type $type): IsSuperTypeOfResult
   	{
   		/** @var TBound $bound */
   		$bound = $this->getBound();
   		if (
   			!$type instanceof $bound
   			&& !$this instanceof $type
   			&& !$type instanceof TemplateType
   			&& ($type instanceof UnionType || $type instanceof IntersectionType)
   		) {
   			return $type->isSuperTypeOf($this);
   		}
   
   		if (!$type instanceof TemplateType) {
   			return $type->isSuperTypeOf($this->getBound());
   		}
   
   		if ($this->getScope()->equals($type->getScope()) && $this->getName() === $type->getName()) {
   			return $type->getBound()->isSuperTypeOf($this->getBound());
   		}
   
   		return $type->getBound()->isSuperTypeOf($this->getBound())
   			->and(IsSuperTypeOfResult::createMaybe());
   	}
   

   so we're doing

   if (!$type instanceof TemplateType) {
        return $type->isSuperTypeOf($this->getBound());
   }
   

   which is $int->isSuperTypeOf($benevolentUnionIntOrString) which is YES.

   That's the issue with using a Benevolent bound...
7. ondrejmirtes

   added

   bug

   on Sep 12, 2025
8. ondrejmirtes

   added this to the Generics milestone on Sep 12, 2025
9. phpstan-bot commented on Sep 9, 2026

   

   phpstan-bot

   on Sep 9, 2026

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   Closed via merging phpstan/phpstan-src#6376
10. phpstan-bot

    closed this as completedon Sep 9, 2026
11. github-actions commented on Oct 11, 2026

    

    github-actionsBot

    on Oct 11, 2026 – with GitHub Actions

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    This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.
12. github-actions

    locked as resolved and limited conversation to collaborators on Oct 11, 2026