Bug report

When using azjezz/psl, the Psl\Type\union() is used to create a union type out of two (or more) Psl\Type\TypeInterface<T> instances.

Roughly: function union(TypeInterface<T>, TypeInterface<U>): TypeInterface<T|U>.

This works fine, but PHPStan seems to have trouble in computing union types for somehow close types like int and numeric-string, leading to inference of int|string rather than int|numeric-string.

Similarly, it cannot compute 0 and positive-int, leading to int being inferred, rather than 0|int<1, max> or int<0, max>.

Code snippet that reproduces the problem

https://phpstan.org/r/749e7db4-8d56-4d2d-9faa-1d3d32790ba0

Expected output

• union(int, numeric-string) should become int|numeric-string (currently produces int|string)
• union(0, int<1, max>) should become 0|int<1, max> (currently produces int)

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