The `AggregateKind` enum ends up in the final mir `Body`. Currently,
any changes to `AdtDef` (regardless of how significant they are)
will legitimately cause the overall result of `optimized_mir` to change,
invalidating any codegen re-use involving that mir.

This will get worse once we start hashing the `Span` inside `FieldDef`
(which is itself contained in `AdtDef`).

To try to reduce these kinds of invalidations, this commit changes
`AggregateKind::Adt` to store just the `DefId`, instead of the full
`AdtDef`. This allows the result of `optimized_mir` to be unchanged
if the `AdtDef` changes in a way that doesn't actually affect any
of the MIR we build.

Add `UnwindSafe` to `Once`

Fixes rust-lang#43469

disable test with self-referential generator on Miri

Running the libcore test suite in Miri currently fails due to the known incompatibility of self-referential generators with Miri's aliasing checks (rust-lang/unsafe-code-guidelines#148). So let's disable that test in Miri for now.

Fixed a small typo in ui test comments

Store a `DefId` instead of an `AdtDef` in `AggregateKind::Adt`

The `AggregateKind` enum ends up in the final mir `Body`. Currently,
any changes to `AdtDef` (regardless of how significant they are)
will legitimately cause the overall result of `optimized_mir` to change,
invalidating any codegen re-use involving that mir.

This will get worse once we start hashing the `Span` inside `FieldDef`
(which is itself contained in `AdtDef`).

To try to reduce these kinds of invalidations, this commit changes
`AggregateKind::Adt` to store just the `DefId`, instead of the full
`AdtDef`. This allows the result of `optimized_mir` to be unchanged
if the `AdtDef` changes in a way that doesn't actually affect any
of the MIR we build.

Update books

## nomicon

1 commits in 49681ea4a9fa81173dbe9ffed74b4d4a35eae9e3..c05c452b36358821bf4122f9c418674edd1d713d
2021-11-24 16:27:28 +0900 to 2021-12-13 15:23:48 +0900
- Update the guidance on uninitialized data with ptr::addr_of_mut (rust-lang/nomicon#325)

## reference

3 commits in 954f3d441ad880737a13e241108f791a4d2a38cd..06f9e61931bcf58b91dfe6c924057e42ce273ee1
2021-11-29 11:11:30 -0800 to 2021-12-17 07:31:40 -0800
- keep consistent for primitive types (rust-lang/reference#1118)
- README.md: link to mdbook docs (rust-lang/reference#1117)
- Say that `...` range patterns are rejected in the 2021 edition (rust-lang/reference#1114)

## book

4 commits in 5f9358faeb1f46e19b8a23a21e79fd7fe150491e..8a0bb3c96e71927b80fa2286d7a5a5f2547c6aa4
2021-12-05 21:33:16 -0500 to 2021-12-22 20:54:27 -0500
- Propagate edits back
- Fix number disagreement. Fixes rust-lang/book#2858.
- Wrap some code in main to make scopes clearer. Fixes rust-lang/book#2830.
- Respond to ch5 nostarch edits

## rustc-dev-guide

9 commits in a374e7d8bb6b79de45b92295d06b4ac0ef35bc09..9bf0028b557798ddd07a6f652e4d0c635d3d6620
2021-12-03 09:26:47 -0800 to 2021-12-20 21:53:57 +0900
- remove rustfix item in test intro (rust-lang/rustc-dev-guide#1277)
- Move date-check comment to fix Markdown syntax
- Update humor docs for special-casing ferris emoji
- Fix some broken links (rust-lang/rustc-dev-guide#1274)
- Update rustdoc internals
- Update HIR chapter to use `HirId` instead of `NodeId`
- Fix some broken links
- Update src/getting-started.md
- Improve documentation on r?