Fix phpstan/phpstan#11488: Wrongly assumed undefined variable since 1.11.10

[phpstan-bot]

Summary

When using count() to narrow a union of constant array types (e.g., array{mixed}|array{mixed, string|null, mixed}), the falsey branch (e.g., count($row) !== 1) incorrectly narrowed the type to *NEVER* instead of the expected non-matching array type. This caused false positive "undefined variable" errors when destructuring the narrowed array.

Changes

• Modified specifyTypesForCountFuncCall in src/Analyser/TypeSpecifier.php to use a direct type assignment (via setAlwaysOverwriteTypes()) for the falsey context when all arrays in the union have definite (fixed) sizes
• Tracked non-matching array types separately during the loop, so the falsey path can directly assign the complement set rather than relying on TypeCombinator::remove
• Added regression test in tests/PHPStan/Analyser/nsrt/bug-11488.php

Root cause

ConstantArrayType::isSuperTypeOf uses structural subtyping: array{mixed} is considered a supertype of array{mixed, string|null, mixed} because every key in the smaller array exists in the larger one with compatible value types. This is intentional for general type checking, but it caused TypeCombinator::remove to be overly aggressive when removing matching count types — it would remove the entire union (producing *NEVER*) instead of just the matching member.

The fix avoids TypeCombinator::remove entirely for this case by collecting non-matching array types and directly assigning them as the narrowed type.

Test

Added tests/PHPStan/Analyser/nsrt/bug-11488.php with three test methods covering:

• count($row) !== 1 narrowing with array{mixed}|array{mixed, string|null, mixed}
• Same narrowing with array{bool}|array{mixed, string|null, mixed}
• count($row) === 3 truthy narrowing

Fixes phpstan/phpstan#11488