rustdoc: indicate when a trait has non-defaulted hidden items #138697
Description
There’s a pattern of hiding a non-defaulted item in a trait to mark it as non-implementable, e.g. inventory::Collect:
This is primarily useful when a trait is implemented by a macro, so it can’t be properly sealed, but still needs to be only implementable by code “originating” in the same crate. It has some similarity with #[non_exhaustive] attribute.
Some options on how this could look:
