[Issue 22579] betterC errors are issued by the glue layer and hence skipped without codegen

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=22579

--- Comment #5 from moonlightsentinel at disroot.org ---
(In reply to Andrei Alexandrescu from comment #0)
> A top-level unittest that is not marked with @betterC in Phobos causes no
> trouble in betterC mode. However, inside a template that's not the case:

@betterC is not a language / compiler feature. It's an "user" (druntime/phobos)
defined annotation used by the test_extractor to mark unittests that should be
tested in a generated module compiled with -betterC.

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