[Issue 12199] RedBlackTree problematic with non-string predicates

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=12199
Issue 12199 depends on issue 12225, which changed state.

Issue 12225 Summary: Alias and value template overloading with function argument
https://issues.dlang.org/show_bug.cgi?id=12225

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

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