Generic not widening based on return type #15417

Bug report

See example here: https://phpstan.org/r/bdba8ec5-b1df-4ff2-a5d3-e3c0bca0b890

Note that changing the return type to Collection<int, object{ch: string, x: Collection<0|1|2|3, object{t: string}>}> resolves the issue.

Code snippet that reproduces the problem

https://phpstan.org/r/bdba8ec5-b1df-4ff2-a5d3-e3c0bca0b890

Expected output

It feels like this is being too overzealous in terms of constraining the generic based on what is ultimately an implementation detail.

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