`Derive(MemDbg)` makes trait non-object safe

[RagnarGrootKoerkamp]

MemDbg:mem_dbg{,_depth}_on functions take a &mut impl Write, which prevent doing &dyn MyTrait when MyTrait: MemDbg.

Not quite sure what a good fix is though. Clearly you want to provide the custom writer functionality.

[zommiommy]

I think the easiest solution is to pass around the writer as owned instead of taking the reference

[RagnarGrootKoerkamp]

You could also take a &mut dyn Write, but that could be considered ugly in cases where it's not necessary.

[RagnarGrootKoerkamp]

Oh probably it would make more sense for the default mem_dbg function to write to stderr rather than stdout.