[Issue 21243] Allow lambdas to return auto ref

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21243

Andrei Alexandrescu <andrei at erdani.com> changed:

           What    |Removed                     |Added
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                 CC|                            |andrei at erdani.com

--- Comment #1 from Andrei Alexandrescu <andrei at erdani.com> ---
Example per Paul:

void main()
{
    alias f1(alias x) = () => x;
    int n = 123;
    assert(__traits(compiles, f!123())); // ok
    assert(__traits(compiles, f!n() = 456)); // no good  
}

If we add ref to the return value of the lambda, the other assertion fails.

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