[Issue 23101] [std.sumtype] canMatch does not account ref

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23101

--- Comment #1 from João Lourenço <jlourenco5691 at gmail.com> ---
Because of this, when matching, `canMatch` will fail as it will test for a
copy, and returning a reference of that value results in escaping it.

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