Temporaries created with `MirPatch::new_temp` will be declared after
patch application. Remove manually created duplicate declarations.

Removing duplicates exposes another issue. Visitor elaborates
terminator twice and attempts to access new, but not yet available,
local declarations. Remove duplicated call to `visit_terminator`.

Error on broken pipe but do not backtrace or ICE

Windows will report a broken pipe as a normal error which in turn `println!` will panic on. Currently this causes rustc to produce a backtrace and ICE. However, this is not a bug with rustc so a backtrace is overly verbose and ultimately unhelpful to the user.

Kind of fixes rust-lang#98700. Although this is admittedly a bit of a hack because at panic time all we have is a string to inspect. On zulip it was suggested that libstd might someday provide a way to indicate a soft panic but that day isn't today.

…iser

Add more `// unit-test`s to MIR opt tests

I only changed things which are hopefully completely uninteresting. I plan to submit more PRs that cover more files, but those cases will need some more complicated (and hence possibly controversial) changes, so I'll try and submit those in reasonably sized batches.

r? rust-lang/wg-mir-opt

…ixups, r=davidtwco

Some "this expression has a field"-related fixes

Each commit does something different and is worth reviewing, but the final diff from `master..HEAD` contains the sum of the changes to the UI tests, since some commits added UI tests "regressions" which were later removed in other commits.

The only change I could see adding on top of this is suppressing `Clone::clone` from the "this expression has a field that has this method" suggestion, since it's so commonly implemented by types that it's not worthwhile suggesting in general.

…gisa

 Remove duplicated temporaries creating during box derefs elaboration

Temporaries created with `MirPatch::new_temp` will be declared after
patch application. Remove manually created duplicate declarations.

Removing duplicates exposes another issue. Visitor elaborates
terminator twice and attempts to access new, but not yet available,
local declarations. Remove duplicated call to `visit_terminator`.

Extracted from rust-lang#99946.

Do not manually craft a span pointing inside a multibyte character.

Fixes rust-lang#92462

Set tainted errors bit before emitting coerce suggestions.

Fixes rust-lang#100246.

rust-lang#89576 basically got 99% of the way there but the match typechecking code (which calls `coerce_inner`) also needed a similar fix.

…=Dylan-DPC

Remove more Clean trait implementations

Follow-up of rust-lang#99638.

r? `@Dylan-DPC`