[Issue 17927] [scope] `scope inout` parameter value can be escaped via return

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17927

--- Comment #10 from Martin Nowak <code at dawg.eu> ---
Thanks for investigating, so now it's reduced to the old problem that the scope
system does not allow to define entry points.
Of course in real life this is using malloc instead of GC'ed dup, but it's not
possible to contain the former.

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