This is a cleanup that doesn't introduce new query calls, but this way `def_key` is decoded twice which may matter for performance or may not

Includes resolving the FIXMEs in the documentation,
and some very minor documentation improvements.

…r=oli-obk

Suppress `opaque_hidden_inferred_bound` for nested RPITs

They trigger too much, making repos like linkerd/linkerd2-proxy#2275 sad.

Ideally, at least for RPITs (and probably TAITs?), specifically when we have `impl Trait<Assoc = impl ..>`, that nested opaque should have the necessary `Assoc` item bounds elaborated into its own item bounds. But that's another story.

r? ``@oli-obk``

…r=BoxyUwU

Refine error spans for const args in hir typeck

Improve just a couple of error messages having to do with mismatched consts.

r? ``@ghost`` i'll put this up when the dependent commits are merged

resolve: Querify most cstore access methods (subset 2)

These changes are less likely to cause perf regressions than the rest of rust-lang#108346.

add `known-bug` test for unsoundness issue

Test for rust-lang#97156

…xyUwU,lcnr

Make alias-eq have a relation direction (and rename it to alias-relate)

Emitting an "alias-eq" is too strict in some situations, since we don't always want strict equality between a projection and rigid ty. Adds a relation direction.

* I could probably just reuse this [`RelationDir`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_infer/infer/combine/enum.RelationDir.html) -- happy to uplift that struct into middle and use that instead, but I didn't feel compelled to... 🤷
* Some of the matching in `compute_alias_relate_goal` is a bit verbose -- I guess I could simplify it by using [`At::relate`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_infer/infer/at/struct.At.html#method.relate) and mapping the relation-dir to a variance.
* Alternatively, I coulld simplify things by making more helper functions on `EvalCtxt` (e.g. `EvalCtxt::relate_with_direction(T, T)` that also does the nested goal registration). No preference.

r? ``@lcnr`` cc ``@BoxyUwU`` though boxy can claim it if she wants
NOTE: first commit is all the changes, the second is just renaming stuff

…apkin

Simpler checked shifts in MIR building

Doing masking to check unsigned shift amounts is overcomplicated; just comparing the shift directly saves a statement and a temporary, as well as is much easier to read as a human.  And shifting by unsigned is the canonical case -- notably, all the library shifting methods (that don't support every type) take shift RHSs as `u32` -- so we might as well make that simpler since it's easy to do so.

This PR also changes *signed* shift amounts to `IntToInt` casts and then uses the same check as for unsigned.  The bit-masking is a nice trick, but for example LLVM actually canonicalizes it to an unsigned comparison anyway <https://rust.godbolt.org/z/8h59fMGT4> so I don't think it's worth the effort and the extra `Constant`.  (If MIR's `assert` was `assert_nz` then the masking might make sense, but when the `!=` uses another statement I think the comparison is better.)

To review, I suggest looking at rust-lang@2ee0468 first -- that's the interesting code change and has a MIR diff.

My favourite part of the diff:
```diff
-        _20 = BitAnd(_19, const 340282366920938463463374607431768211448_u128); // scope 0 at $DIR/shifts.rs:+2:34: +2:44
-        _21 = Ne(move _20, const 0_u128); // scope 0 at $DIR/shifts.rs:+2:34: +2:44
-        assert(!move _21, "attempt to shift right by `{}`, which would overflow", _19) -> [success: bb3, unwind: bb7]; // scope 0 at $DIR/shifts.rs:+2:34: +2:44
+        _18 = Lt(_17, const 8_u128);     // scope 0 at $DIR/shifts.rs:+2:34: +2:44
+        assert(move _18, "attempt to shift right by `{}`, which would overflow", _17) -> [success: bb3, unwind: bb7]; // scope 0 at $DIR/shifts.rs:+2:34: +2:44
```

…, r=joshtriplett

Stabilize `arc_into_inner` and `rc_into_inner`.

Stabilize the `arc_into_inner` and `rc_into_inner` library features and thus close rust-lang#106894.

The changes in this PR also resolve the FIXMEs for adjusting the documentation upon stabilization, and I’ve additionally included some very minor documentation improvements.

``@rustbot`` label +T-libs-api -T-libs

…ng, r=compiler-errors

make param bound vars visibly bound vars with -Zverbose

I was trying to debug some type/const bound var stuff and it was shockingly tricky due to the fact that even with `-Zverbose` enabled the `T` in `for<T> T: Trait` prints as `T` making it seem like its `TyKind::Param` when it is infact `TyKind::Bound`. This PR "fixes" this when `-Zverbose` is set to allow rendering it as `^T` or `^1_T` depending on binder depth.

r? ``@compiler-errors``