`mk_obligation_for_def_id` is only correct if the trait and self type do
not have any substitutions. Use a different method,
`mk_trait_obligation_with_new_self_ty` that is more clear about what is
happening.

Otherwise inserting it to the `Binder` used by `trait_ref` would cause
problems. This is just to be extra carefult: we aren't going to
start recommending that the user start using HKTs anytime soon.

Fixes rust-lang#72386

This type also needs to get allocated on the `librustc_middle` arena
when we deserialize MIR.

…atsakis

Preserve substitutions when making trait obligations for suggestions

Resolves rust-lang#71394.

I *think* `map_bound_ref` is correct here. In any case, I think a lot of the diagnostic code is using `skip_binder` more aggressively than it should be, so I doubt that this is worse than the status quo. The assertion that `new_self_ty` has no escaping bound vars should be enough.

r? @estebank

cc @nikomatsakis Is the call to `skip_binder` on line 551 (and elsewhere in this file) appropriate? https://github.com/rust-lang/rust/blob/46ec74e60f238f694b46c976d6217e7cf8d4cf1a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs#L537-L565

…Gomez

Unblock font loading in rustdoc.css

rustdoc's font loading defaults to "auto", so browsers may block render.
But rustdoc's case prefers a faster TTI for scrolling, this means the
strictest font-display in use should be "swap". rustdoc's fonts do provide
notable legibility improvements but first-time users will have little trouble
reading without. This means "optional" is preferred.

The one exception is Source Serif Pro: it's a big difference for body text, so
"fallback" is preferred over "optional" to cause a (tiny) block.

This follows up on (but does not resolve) rust-lang#20962, taking PageSpeed Insight's rec fairly directly. Supporting reading material: https://drafts.csswg.org/css-fonts-4/#font-display-desc

Add missing ASM arena declarations to librustc_middle

Fixes rust-lang#72386

These types also need to get allocated on the `librustc_middle` arena
when we deserialize MIR.

@Amanieu: If we end up using your approach in rust-lang#72392 instead, feel free to copy the test I added over to your PR.

Fix ice-72487

Fixes rust-lang#72487

r? @Amanieu

…s-schievink

fix discriminant type in generator transform

The generator transform assumed that the discriminant type is always `isize`, which is not correct, leading to [ICEs in Miri](https://github.com/rust-lang/rust/pull/72419/files#r429543536) when some extra sanity checking got enabled.

r? @jonas-schievink @eddyb