[Issue 23382] Non-template requirement for copy constructors is undocumented

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23382

--- Comment #1 from Paul Backus <snarwin+bugzilla at gmail.com> ---
PR: https://github.com/dlang/dlang.org/pull/3427

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