[Issue 21886] case where member function used as "alias this sym" is allowed without right `this` context

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21886

--- Comment #1 from Basile-z <b2.temp at gmx.com> ---
This is actually conform with the code of resolveAliasThis(),
https://github.com/dlang/dmd/blob/b8ffb017c8c802827be98722b838cb120b9d918b/src/dmd/aliasthis.d#L83-L101

But the specs are not in sync with that.

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