Deprecate callStructDtorsDuringGC

[edi33416]

Please see #2509 for related discussion.

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[wilzbach]

Changlog entry...

[rainers]

It doesn't help to print the deprecation when compiling druntime, it must be printed when the option is used, i.e. here: https://github.com/dlang/druntime/pull/2513/files#diff-50840eb79e3292d148af41006e3af980R51

[andralex]

I think this message will be printed while druntime is built, i.e. it is not client-visible at all. Its helpfulness is limited.

A better way to go about this is to detect the situation when user code is attempting to set that variable to false, and emit a deprecation message at that time (i.e. at run time).

[andralex]

@rainers saw yours after I typed in mine...

[rainers]

Message still printed at the wrong time (when compiling druntime rather than when it is used).

[JinShil]

Message still printed at the wrong time (when compiling druntime rather than when it is used).

But how does one print a deprecation warning at runtime? fprintf(stderr, ...)?

[rainers]

fprintf(stderr, ...)?

Yes.

[JinShil]

#2743 was merged so I believe this can now be closed.

[thewilsonator]

Please reopen if this is still required.