[Issue 13423] Allow covariant assignment of lambda to delegate variable

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=13423

--- Comment #3 from hsteoh at quickfur.ath.cx ---
Oops, looks like I made a mistake while reducing the original test case. I'll
have to go back and re-reduce it. Sorry for the noise.

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