[Issue 21500] public import in mixin template in module a fails when module b imports a.

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21500

--- Comment #4 from RazvanN <razvan.nitu1305 at gmail.com> ---
(In reply to Max Samukha from comment #3)
> How are imported symbols different than other symbols introduced by a mixin?

In the case of imported symbols, you are right, there isn't any difference,
however, the problematic case is when you have module imports (`import
std.stdio`) inside a mixin. In that case, you end up importing a lot of symbols
that you have no idea about. The user can look through the code (or the
documentation) of a mixin template and at least have a general understanding of
the symbols that he is mixing in, whereas, in the case of imports there is no
way you can know what symbols end up hijacking your other symbols (except if
you audit all the imported modules).

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