[Issue 23445] Can leak scope variable through delegate context

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23445

Walter Bright <bugzilla at digitalmars.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |bugzilla at digitalmars.com
         Resolution|---                         |INVALID

--- Comment #1 from Walter Bright <bugzilla at digitalmars.com> ---
Reducing to:

int global;
int* foo(scope int* p)@safe{
    auto dg=(return scope int* q)@safe return scope{
        return p;
    };
    return dg(&global);  <== returns a pointer to p
}

This is not a problem, because the compiler recognizes the escape of p and
allocates p in a closure on the heap. This heap allocate is done whenever a
nested function is turned into a delegate.

For nested functions not turned into a delegate, p is placed in a heap
allocated closure, and an error is produced for `return dg(&global);`

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