When encountering `-> Trait`, suggest `-> Box<dyn Trait>` (instead of `-> Box<Trait>`.
If there's a single returned type within the `fn`, suggest `-> impl Trait`.
Invert infer `error_reporting` mod struture
Parallel change to #127493, which moves `rustc_infer::infer::error_reporting` to `rustc_infer::error_reporting::infer`. After this, we should just be able to merge this into `rustc_trait_selection::error_reporting::infer`, and pull down `TypeErrCtxt` into that crate. 👍
r? lcnr
This commit changes the error reporting mechanism for not implemented
traits to skip impl marked as `#[diagnostic::do_not_recommend]` in the
help part of the error message ("the following other types implement
trait `Foo`:"). The main use case here is to allow crate authors to skip
non-meaningful confusing suggestions. A common example for this are
fully generic impls on tuples.
