#58972 ignored extern_traits because before #65983 was fixed, they
would always fail to resolve, giving spurious warnings.
This undoes that change, so extern traits are now seen by the
`collect_intra_doc_links` pass. There are also some minor changes in
librustdoc/fold.rs to avoid borrowing the extern_traits RefCell more
than once at a time.
Currently dependency crates of the standard library can sometimes leak
into error messages such as when traits to import are suggested.
Additionally they can leak into documentation such as in the list of
"all traits implemented by `u32`". The dependencies of the standard
library, however, are intended to be private.
The dependencies of the standard library can't actually be stabl-y
imported nor is the documentation that relevant since you can't import
them on stable either. This commit updates both the compiler and rustdoc
to ignore unstable traits in these two scenarios.
Specifically the suggestion for traits to import ignore unstable traits,
and similarly the list of traits implemented by a type excludes unstable
traits.
This commit is extracted from #73441 where the addition of some new
dependencies to the standard library was showed to leak into various
error messages and documentation. The intention here is to go ahead and
land these changes ahead of that since it will likely take some time to
land.
Remove spotlight
I had a few comments saying that this feature was at best misunderstood or not even used so I decided to organize a poll about on [twitter](https://twitter.com/imperioworld_/status/1232769353503956994). After 87 votes, the result is very clear: it's not useful. Considering the amount of code we have just to run it, I think it's definitely worth it to remove it.
r? @kinnison
cc @ollie27
* Generate links to the primitive type docs for re-exports.
* Don't ICE on cross crate primitive type re-exports.
* Make primitive type re-exports show up cross crate.
Use named fields for `{ast,hir}::ItemKind::Impl`
Currently, the widely used `ItemKind::Impl` variant is a tuple with seven fields. I want to add an eighth in #68140, which means I have to update most matches on this variant anyways. Giving a name to each field improves readability and makes future changes of this nature much simpler.
This change will cause several tools to break. I will fix them once this is merged.
rustc: arena-allocate the slice in `ty::GenericsPredicate`, not the whole struct.
While rebasing #59789 I noticed we can do this now. However, it doesn't help much without changing `inferred_outlives_of` to the same type, which I might try next.
