…em in constant contexts

This purges uses of uninitialized where possible from test cases. Some
are merely moved over to the equally bad pattern of
MaybeUninit::uninit().assume_init() but with an annotation that this is
"the best we can do".

Co-Authored-By: Ralf Jung <[email protected]>

The function is never used inside lowering,
but only ever in external crates.

By moving it, we faciliate lowering as its own crate.

Add PartialEq and Eq to Cursor

closes rust-lang#67226

Require const stability attributes on intrinsics to be able to use them in constant contexts

r? @Centril

finally fixes rust-lang#61495

cc @RalfJung

…tril

Remove mem::uninitalized from tests

This purges uses of uninitialized where possible from test cases. Some
are merely moved over to the equally bad pattern of
MaybeUninit::uninit().assume_init() but with an annotation that this is
"the best we can do".

Fixes rust-lang#62397

…h, r=kinnison

Results show too much

Fixes rust-lang#67461.

To reproduce the current issue: search anything, then once the results appears, press escape. They should disappear then re-appear right away. This is because blurring an element triggers the "change" event.

r? @kinnison

…rk-Simulacrum

Move `{hir::lowering -> hir}::is_range_literal`

The function is never used inside lowering, but only ever in external crates.
By moving it, we facilitate lowering as its own crate.

Best read commit-by-commit.

r? @Mark-Simulacrum

…ntril

Improve diagnostics for invalid assignment

- Improve wording and span information for invalid assignment diagnostics.
- Link to rust-lang/rfcs#372 when it appears the user is trying a destructuring assignment.
- Make the equality constraint in `where` clauses error consistent with the invalid assignment error.

Fix ICE in mir interpretation

Indices from the end start at 1 so you can immediately subtract them from the length to get the index instead of having to do an additional `-1`. Kinda documented in https://doc.rust-lang.org/nightly/nightly-rustc/rustc/mir/enum.ProjectionElem.html#variant.ConstantIndex

Document that calling Drop, even after it panics, is UB

Fixes rust-lang#60822.

r? @gnzlbg