Normalize array keys through toArrayKey() in array_fill_keys and array_combine return types

[phpstan-bot]

Summary

Documenting an array key as int|decimal-int-string normalizes to int, but array_fill_keys() did not perform this normalization on its result, producing array<int|decimal-int-string, ...>. Assigning that to an array<int, ...> property triggered a false positive. The fix runs the computed key type through Type::toArrayKey(), which coerces integer-like string keys to int exactly like PHP does at runtime.

Changes

• src/Type/ArrayType.php — fillKeysArray() now returns new ArrayType($keyType->toArrayKey(), $valueType) in both branches, so the resulting key type is coerced the way PHP coerces array keys (this matches flipArray(), which already used toArrayKey()).
• src/Type/MixedType.php — fillKeysArray() normalizes the key type through toArrayKey() as well, so array_fill_keys() on a mixed array produces an int|string key instead of mixed.
• src/Type/Php/ArrayCombineHelper.php — the non-constant array_combine() path had the same missing normalization; the key type is now passed through toArrayKey().
• Updated test expectations in array-fill-keys.php, array-fill-keys-php8.php and array-combine-php8.php that asserted the previous, un-normalized keys.
• Added tests/PHPStan/Analyser/nsrt/bug-14980.php.

Root cause

array_fill_keys() (and array_combine(), and array_fill_keys() on mixed) use the input array's values as keys. PHP coerces those values with the usual array-key rules (decimal-int-strings become int, floats/bools/objects are stringified first, then re-coerced). PHPStan's Type::toArrayKey() models exactly this coercion, and array_flip()/array_count_values()/array_column() already used it — but the array_fill_keys and non-constant array_combine paths built the key type with toString() (or returned it verbatim) and never applied toArrayKey(). As a result the refinement (decimal-int-string, plain mixed, un-truncated floats, bool) leaked into the key type. The pattern is "value-as-key array functions must normalize the key through toArrayKey()"; every affected location now does.

Test

• bug-14980.php asserts array_fill_keys() on list<int|decimal-int-string> yields array<int, true> (the reported case), plus the numeric-string, mixed-array and array_combine analogues.
• Existing array-fill-keys / array-combine fixtures were updated to the now-correct normalized keys (float keys include int, bool keys collapse to int|string, decimal-int-string keys collapse to int).

Fixes phpstan/phpstan#14980