Idea: Conditional code based on whether a type implements a trait

[scottmcm]

@KSXGitHub

I sometimes want to log values inside a generic function, but can't, because the type does not have std::fmt::Debug as a trait constraint.

I suggest you check out this thread from a few days ago:

Pre-RFC: MaybeDebug<T> type which always `impl Debug`

Please let me know what you're thinking about it. Also, should I keep the empty sections on real RFC? Summary Adds struct MaybeDebug<T>(&T);. which implements Debug trait regardless whether the T implements it. Motivation Debug trait is used for the programmer-facing, debugging context formatting. Most public types implements this trait to enable casual debugging. But since it's a regular trait not something built into the language, you need to explicitly adds trait bound to use it in the ge…