[HawkForge]

Closes phpstan/phpstan#15450

Thanks @lucianofedericopereira for the report.

array_is_list() is stubbed as ($value is list ? true : false). For array<string, mixed>, list<mixed> (array<int<0, max>, mixed> & AccessoryArrayListType) answered no from IntersectionType::isSuperTypeOf(), because the key types are disjoint and ArrayType::isList() is no. That ignores [], which is both a list and a valid array<string, mixed>. So the call was reported as always false, and narrowing the true branch through TypeCombinator::intersect() returned *NEVER* because the two ArrayType members are disjoint.

Changes:

• IntersectionType::isSuperTypeOf(): when a list type would answer no for an array that is not a list (isList()->no()), the answer becomes maybe if both sides admit []. A non-empty-array<string, mixed> does not admit [], so it stays no (as requested in the issue).
• TypeCombinator::intersect(): when two array members are disjoint, one of them can never be a list, the intersection contains AccessoryArrayListType, and both admit [], the result is array{} intersected with the remaining members instead of never.
• The same changes are mirrored in turbo-ext/src/IntersectionType.cpp and turbo-ext/src/TypeCombinator.cpp.

The fix is limited to list-ness on purpose. Generic arrays with disjoint key or value types (array<int, string> & array<string, string>, list<A> vs list<B>) behave as before. The existing TypeCombinatorTest cases and the MethodSignatureRule messages still pass unchanged.

Tests:

• New tests/PHPStan/Analyser/nsrt/bug-15450.php (the issue's reproducer) asserts array{} / non-empty-array<string, mixed> for array<string, mixed>, and *NEVER* for non-empty-array<string, mixed>.
• ImpossibleCheckTypeFunctionCallRuleTest::testArrayIsList no longer expects the error for array<string, int>. A new non-empty-array<string, int> case keeps the error.
• nsrt/bug-14177.php: list{0: string, 1?: string, 2?: string, 3?: string} after unset($b[$int]) is array{0?: string, ...}, so array_is_list() is bool, not false. At runtime $b = ['x']; unset($b[0]); leaves [], and array_is_list() returns true.

Without the source change, the new nsrt test, the updated bug-14177 assertion and testArrayIsList all fail.