[Issue 21625] Mixed-in unittests can collide with other unittests

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21625

--- Comment #4 from Basile-z <b2.temp at gmx.com> ---
There should not be conflicts. DMD has a special function in its Identifier
class that was exactly designed to prevent such conflicts. That's why you see
"L" and "C" in the mangle BTW, so definitively a bug.

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