discuss/resolve fn { mod { (use) super::...; } } and its interaction with derive patterns

[pnkfelix]

Summary

There's a future-incompat lint, proc_macro_derive_resolution_fallback (rust-lang/rust#83583), which seemed like a slam dunk, but moving it to a hard error had unexpected repercussions due to a slight expressiveness limitation, "Paths involving 'super' don't work from within a function" (rust-lang/rust#64079).

I want to meet to survey the solutions (I believe two have been proposed and I want to put forward at least a third) and evaluate whether to push aggressively to re-hard-error proc_macro_derive_resolution_fallback or if we want to make some language change first to better serve authors of derive macros.

Background reading

pnkfelix will prepare a doc.

but in the meantime, there are the links in the description given above.

About this issue

This issue corresponds to a lang-team design meeting proposal. It corresponds to a possible topic of discussion that may be scheduled for deeper discussion during one of our design meetings.

[pnkfelix]

currently scheduled for 2023-02-15