[Issue 10785] Interface diamond covariance causes silent breakage

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=10785
Issue 10785 depends on issue 10806, which changed state.

Issue 10806 Summary: Interface covariance for more than one interface at once also broken
https://issues.dlang.org/show_bug.cgi?id=10806

           What    |Removed                     |Added
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             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED

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