Empty string and generics union type parameter issue

[koriym]

Bug report

Empty string and generics union type parameter does not accept an empty string.

''|class-string union type parameter accepts empty-string, but not with ''|class-string<T> parameter.

Code snippet that reproduces the problem

/**
 * @param ''|class-string<T> $p
 * @template T of object
 */
function ng($p): void
{
}

ng('');

Parameter #1 $p of function ng expects class-string<>, string given.

https://phpstan.org/r/c4e8c2a7-59a6-4863-94e4-48b0a02b7af3

Expected output

No error.

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[phpstan-bot]

@koriym After the latest push in 1.8.x, PHPStan now reports different result with your code snippet:

@@ @@
-19: Parameter #1 $p of function ng expects class-string<>, string given.
+No errors

[staabm]

regression test incoming

[github-actions]

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