Is there any way to fallback Debug?

[cole-miller]

This comes up periodically; the usual suggestion is to use the (unstable, nightly-only) specialization feature, as in these posts:

Use the dbg!(...) macro without requiring the Debug trait in parent functions?

Something like this seems like a very reasonably application of the unstable specialization feature. Since you’re only caring about debugging anyways, perhaps you’re fine with using a nightly compiler for the debugging. In this case, you can do something like this: Rust Playground

[SOLVED] Put trait bound Debug on generic type only during development

You can use specialization to reach Debug impls, even if you don't have the bound. I'm going to use this for debugging a lot. Playground example here That's the brave new world of non-parametricity.