[Issue 17318] Delegates allow escaping reference to stack variable

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=17318

--- Comment #3 from hsteoh at quickfur.ath.cx ---
P.S. On my computer, the value of z changes after the call to dg(), which is
wrong because z is a local variable in smoke() that the delegate should not be
able to access.

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