Introduce 'ra lifetime name.

[nnethercote]

rustc_resolve allocates many things in ResolverArenas. The lifetime used for references into the arena is mostly 'a, and sometimes 'b.

This commit changes it to 'rslv, which is much more descriptive. The commit also changes the order of lifetimes on a couple of structs so that 'rslv is second last, before 'tcx, and does other minor renamings such as 'r to 'a.

r? @petrochenkov
cc @oli-obk

[Noratrieb]

how about 'res, an already common abbreviation for resolution/resolving?

[nnethercote]

I deliberately avoided res because it's also used a lot for "result". But I could live with it, it's certainly better than 'a'.

[petrochenkov]

Technically it's not a lifetime of resolver (i.e. you can't do &'rslv Resolver), it's a lifetime of the arenas and it's larger.
On the other hand 'tcx is also technically not a lifetime of TyCtxt.

I don't like long lifetime names though, as long as 'tcx is probably the limit, the resolver also acts sort of like tcx (i.e. a global context) for a large part of compilation.
Maybe compress it to 3 letters - 'res, 'rcx, 'rsl, 'rsv, 'ra (resolver arenas), ...?

[petrochenkov]

'r is currently used as an actual Resolver lifetime, why renaming it?

[nnethercote]

Maybe compress it to 3 letters - 'res, 'rcx, 'rsl, 'rsv, 'ra (resolver arenas), ...?

I like 'ra, I will switch to that.

'r is currently used as an actual Resolver lifetime, why renaming it?

This is in reference to changes like this one:

-        struct FindReferenceVisitor<'r, 'a, 'tcx> {
-            r: &'r Resolver<'a, 'tcx>,
+        struct FindReferenceVisitor<'a, 'rslv, 'tcx> {
+            r: &'a Resolver<'rslv, 'tcx>,
             impl_self: Option<Res>,
             lifetime: Set1<LifetimeRes>, 
         }

There are a handful of structs where I changed &'r Resolver<...> to &'a Resolver<...>. I did this because I don't think these references are truly specific to the resolver. If another field containing a reference was added to this struct, it's quite likely that it would have the same lifetime. This issue came up in #130022 where several structs had multiple reference fields with the same lifetime, and @oli-obk suggested switching from 'mir (which was appropriate only for the &mir::Body field) to 'a to indicate that the lifetime is more just "a lifetime" rather than a very specific lifetime. E.g. we ended up with this:

pub struct EverInitializedPlaces<'a, 'tcx> {
    body: &'a mir::Body<'tcx>,
    move_data: &'a MoveData<'tcx>,
}

instead of using 'mir. (Lifetime naming is difficult!)

[nnethercote]

I have updated 'rslv to 'ra throughout.

[petrochenkov]

@bors r+

[bors]

📌 Commit d4fc76c has been approved by petrochenkov

It is now in the queue for this repository.