Fix #12244: $this(Type~Subtracted) does not work on conditional return type as Type~Subtracted#5104
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- When a method has a conditional return type like `@return ($this is self::A ? int : null)`, and `$this` has a subtracted type (e.g. `$this(X~X::A)` from narrowing), the conditional was not properly resolved because the subtracted type was not propagated - The root cause was in `StaticType::transformStaticType` which transforms `StaticType` instances in return types but did not propagate the calling type's subtracted type - Added subtracted type propagation in `StaticType::transformStaticType` to match the behavior of `CalledOnTypeUnresolvedMethodPrototypeReflection::transformStaticType` - New regression test in tests/PHPStan/Analyser/nsrt/bug-12244.php Closes phpstan/phpstan#12244
VincentLanglet
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Summary
When a method has a conditional return type referencing
$this(e.g.,@return ($this is self::A ? int : null)) and$thishas been narrowed via type subtraction (e.g., insideif ($this !== self::A)), the conditional return type was not properly resolved. It returnedint|nullinstead ofnull, even though the same narrowing worked correctly for non-$thisvariables.Changes
StaticType::transformStaticType()insrc/Type/StaticType.phpto propagate the calling type's subtracted type when transformingStaticTypeinstances in return typestests/PHPStan/Analyser/nsrt/bug-12244.phpRoot cause
When PHPStan resolves method return types, it transforms
StaticType/ThisTypeinstances in the return type to reflect the actual calling type. For regular object types ($x: X~X::A),CalledOnTypeUnresolvedMethodPrototypeReflection::transformStaticTypereplacesStaticTypewith the full caller type including its subtracted type. However, for$thistypes ($this(X~X::A)),StaticType::transformStaticTypeonly changed the base class ofStaticTypeinstances without propagating the subtracted type from the calling$this. This meant the conditional($this is self::A ? int : null)could not determine that$thiswas definitely notself::A.The fix adds subtracted type propagation in
StaticType::transformStaticType, ensuring consistency with howCalledOnTypehandles the same scenario.Test
Added
tests/PHPStan/Analyser/nsrt/bug-12244.phpwhich tests:$this->get()inside an instance method after narrowing$thisviaif ($this !== self::A)correctly returnsnull$x->get()inside a static method after narrowing$xviaif ($x !== self::A)correctly returnsnull(was already working)Fixes phpstan/phpstan#12244