[Issue 16478] Don't allow to!T() in constraint

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=16478

--- Comment #2 from github-bugzilla at puremagic.com ---
Commit pushed to master at https://github.com/dlang/phobos

https://github.com/dlang/phobos/commit/006ee446f886c5a0f8147908501d287236dd6197
Fix Issue 16478 - Don't allow to!T() in constraint

Also avoid highlighting 'to' unnecessarily.

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