It was unused.

Regions in TypeckTables will be erased, so are unusable for error
reporting.

Also skip duplicated region solving entirely with `-Zborrowck=mir`.

keyword docs for else and inkeyword docs for else and in.

First cut of else and in keyword docs. Comments and suggestions more than welcome.

…an-DPC

clean up E0308 explanation

r? @Dylan-DPC

…komatsakis

Erase regions in writeback

Regions in `TypeckTables` (except canonicalized user annotations) are now erased. Further, we no longer do lexical region solving on item bodies with `-Zborrowck=mir`.

cc rust-lang#68261
r? @nikomatsakis

…nkov

Don't unwind when hitting the macro expansion recursion limit

This removes one use of `FatalError.raise()`.

r? @petrochenkov

…andry

Use smaller discriminants for generators

Closes rust-lang#69815

I'm not yet sure about the runtime performance impact of this, so I'll try running this on some benchmarks (if I can find any). (Update: No impact on the benchmarks I've measured on)

* [x] Add test with a generator that has exactly 256 total states
* [x] Add test with a generator that has more than 256 states so that it needs to use a u16 discriminant
* [x] Add tests for the size of `Option<[generator]>`
* [x] Add tests for the `discriminant_value` intrinsic in all cases

…=oli-obk

Make methods declared by `newtype_index` macro `const`

Crates that use the macro to define an `Idx` type need to enable `#![feature(const_if_match, const_panic)]`.

Build dist-android with --enable-profiler

This will make the runtime available to enable PGO for Rust code in Firefox on Android.

r? @michaelwoerister

…petrochenkov

Fix repr pretty display

Fixes rust-lang#70027.

r? @varkor