Preserve TemplateType in IntersectionType::shuffleArray() when intersection is already a list#5694
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ondrejmirtes merged 1 commit intoMay 18, 2026
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…tersection is already a list - In `IntersectionType::shuffleArray()`, skip calling `shuffleArray()` on `TemplateType` members when the intersection is already a list, since shuffling/sorting a list produces another list with the same structure, so the template identity is preserved. - When the intersection is not a list (e.g. `T&array<string, int>`), template types are still correctly dropped because sorting reindexes keys to list format, changing the array structure. - Update existing test in `sort.php` that asserted the buggy behavior (T being dropped from `T&list<...>` after usort). - Key-preserving sorts (`uasort`, `asort`, `ksort`, etc.) already preserve template types correctly via `makeListMaybe()` since `ArrayType::makeListMaybe()` returns `$this`. - Probed analogous operations (`reverseArray`, `mapValueType`, `popArray`, `shiftArray`, `sliceArray`, `spliceArray`) and confirmed they either already preserve template types or correctly drop them (when the operation genuinely changes array structure).
Contributor
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@phpstan-bot do we have a similar bug in one of the other |
Member
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@staabm Sorry, I was faster, feel free to research it 😊 |
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Summary
When an intersection type like
T&list<int>was passed throughshuffleArray()(used forsort,rsort,usort,shuffle), the template typeTwas lost becauseTemplateArrayType::shuffleArray()(inherited fromArrayType) constructs a new plainArrayType, discarding the template identity. Since sorting a list produces another list with the same key structure,Tshould be preserved.Changes
src/Type/IntersectionType.php: ModifiedshuffleArray()to check whether the intersection is already a list. If so,TemplateTypemembers are passed through unchanged (since list→list preserves key structure). Non-list intersections still drop template types correctly.tests/PHPStan/Analyser/nsrt/bug-14631.php: New regression test covering:usort/sort/rsort/shuffleonT&list<int>→ T preservedusort/sort/rsort/shuffleonT&array<string, int>→ T correctly droppeduasort/asort/ksorton both list and non-list intersections → T always preserved (key-preserving sorts)tests/PHPStan/Analyser/nsrt/sort.php: Updated existing assertion from buggy expectation (T dropped) to correct expectation (T preserved).Root cause
IntersectionType::shuffleArray()calledshuffleArray()on every member type unconditionally. ForTemplateArrayType(which extendsArrayType),shuffleArray()creates a freshArrayType+AccessoryArrayListTypeintersection, losing the template identity. The fix recognizes that when the intersection is already a list, shuffling doesn't change the key structure, so template types can safely be kept.Analogous cases probed
reverseArray:ArrayType::reverseArray()returns$this, so template types are already preserved. No bug.makeListMaybe(key-preserving sorts):ArrayType::makeListMaybe()returns$this, so template types are already preserved. No bug.mapValueType,popArray,shiftArray,sliceArray,spliceArray: These operations genuinely change the array's values or structure, so dropping template types is correct behavior. No bug.Test
The regression test in
bug-14631.phpcovers all combinations of sort type (list-making vs key-preserving) and input type (list intersection vs non-list intersection), verifying template type preservation/dropping in each case.Fixes phpstan/phpstan#14631