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

[d-bugmail at puremagic.com]

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

--- Comment #1 from noobnoobsai at gmail.com ---
Correction:

```bar.d

mixin template baz() {
    public import std.stdio;
    // public import std.stdio : writeln;

}

```

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