[Issue 17934] [scope] scopeness entrypoint for unique/ref-counted missing

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17934

--- Comment #1 from Martin Nowak <code at dawg.eu> ---
Even if `l` is not inferred as scope, it should be a local with limited
lifetime.
The return value `l.front` should have that same lifetime b/c of `return
scope`.
Both of them should be shorter as `elem`, hence assignment should fail.

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