[Issue 18604] in parameter storage class should be deprecated

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18604

--- Comment #4 from anonymous4 <dfj1esp02 at sneakemail.com> ---
Also the reason why safe code receives breakage is because it's invalid, and
there should be no guarantee for invalid code to work.

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