Make array_combine() generic

[b1rdex]

https://phpstan.org/r/59427afd-8dc6-4b14-8d40-2c52b5fc8d34

Currently, array_combine produces array|false. It should be enhanced with this:

/**
 * @template TKey
 * @template TValue
 * @param array<TKey> $keys
 * @param array<TValue> $values
 *
 * @return array<TKey, TValue>|false
 */
array_combine(array $keys, array $values);

[b1rdex]

@ondrejmirtes I'd like to contribute this but I don't get where should I put that stub?

[ondrejmirtes]

Stub files (https://phpstan.org/user-guide/stub-files) are supported above userland classes, userland functions, userland methods, useland properties, builtin classes, builtin methods, built properties, but unfortunately not above builtin functions, there wasn't a use case until now.

So the support for that needs to be added first. For userland functions it was done here phpstan/phpstan-src@7f07659#diff-1cf42bada627951c5878a8529e3f81cc for builtin functions it would have to be done in https://github.com/phpstan/phpstan-src/blob/master/src/Reflection/SignatureMap/NativeFunctionReflectionProvider.php.

[phpstan-bot]

@b1rdex PHPStan now reports different result with your code snippet:

@@ @@
+PHP 8.0 (2 errors)
+==========
+
 11: Cannot access offset 'a' on array<string, int>|false.
-13: Cannot access offset 'a' on array|false.
+24: Method HelloWorld::combine() never returns false so it can be removed from the return typehint.
+
+PHP 7.1 – 7.4 (1 error)
+==========
+
+11: Cannot access offset 'a' on array<string, int>|false.

Full report

PHP 8.0 (2 errors)

Line	Error
11	`Cannot access offset 'a' on array<string, int>
24	Method HelloWorld::combine() never returns false so it can be removed from the return typehint.

PHP 7.1 – 7.4 (1 error)

Line	Error
11	`Cannot access offset 'a' on array<string, int>

[github-actions]

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