Add deref suggestion

Fixes #34562.

Make the fallback of generator resumption be unreachable instead of using return

Record semantic types for all syntactic types in bodies

... and use recorded types in type privacy checking (types are recorded after inference, so there are no `_`s left).
Also use `hir_ty_to_ty` for types in signatures in type privacy checking.

This could also be potentially useful for save-analysis and diagnostics.

Fixes https://github.com/rust-lang/rust/pull/42125#issuecomment-305987755
r? @EddyB

Rollup of 14 pull requests

- Successful merges: #44554, #44648, #44658, #44712, #44717, #44726, #44745, #44746, #44749, #44759, #44770, #44773, #44776, #44778
- Failed merges:

std::sync::RwLock docs improvement

Addresses the `RwLock` part of #29377.
r? @steveklabnik

Added examples, links to types, and a small comparison between RwLock and Mutex.

Link to Rust forge from CONTRIBUTING.md

Add missing links for Arc

r? @rust-lang/docs

Less confusing placeholder when RefCell is exclusively borrowed

Based on ExpHP's comment in [*RefCell.borrow_mut get strange result*](https://users.rust-lang.org/t/refcell-borrow-mut-get-strange-result/12994):

> it would perhaps be nicer if it didn't put something that could be misinterpreted as a valid string value

The previous Debug implementation would show:

    RefCell { value: "<borrowed>" }

The new one is:

    RefCell { value: <borrowed> }

improve english in create_dir_all docs

Just minor nitpicking.

MIR-borrowck: Adding notes to E0503

This PR adds notes to the MIR borrowck error E0503.

Part of #44596

Include unary operator to span for ExprKind::Unary

rustc: Don't use DelimToken::None if possible

This commit fixes a regression from #44601 where lowering attribute to HIR now
involves expanding interpolated tokens to their actual tokens. In that commit
all interpolated tokens were surrounded with a `DelimToken::None` group of
tokens, but this ended up causing regressions like #44730 where the various
attribute parsers in `syntax/attr.rs` weren't ready to cope with
`DelimToken::None`. Instead of fixing the parser in `attr.rs` this commit
instead opts to just avoid the `DelimToken::None` in the first place, ensuring
that the token stream should look the same as it did before where possible.

Closes #44730

Fix librustc/README.md diagram

Make `-Z borrowck-mir` imply that `EndRegion`'s should be emitted.

Before this change, the `-Z borrowck-mir` flag is useless if you do not also pass `-Z emit-end-regions`.

So, in the same spirit as f2892ad2, make `-Z borrowck-mir` also emit `EndRegion` statements. (This will hopefully avoid some initial speed bumps for new-comers helping out with NLL.)

fix an incorrect assertion in the doc example for `std::io::copy`

I think this wasn't caught by CI because the `foo` wrapper function was only defined and not called. This seems to be the norm for doc examples that define a `foo` function. Is that on purpose?

Remove str_eq lang item

It's not really a lang item. Also remove outdated note. The reference uses this as an example so it has to be updated.

Expand size_of docs

This PR does 3 things.

1. Adds a description of what pointer size means to the primitive pages for usize and isize.
2. Says the general size of things is not stable from compiler to compiler.
3. Adds a table of sizes of things that we do guarantee. As this is the first table in the libstd docs, I've included a picture of how that looks.

![](https://i.imgur.com/YZ6IChH.png?1)

Add pub visibility for methods as well

Fixes #44527.

r? @QuietMisdreavus

only set non-ADT derive error once per attribute, not per trait

I found the expansion code very hard to follow, leaving me unsure as to whether this might somehow be done better, but this patch does give us the behavior requested in #43927 (up to exact choice of span; here, it's the entire attribute, not just the `derive` token).

(Note to GitHub robots: _resolves #43927_.)

r? @jseyfried

Use SHA512 for signatures

Fixes #44714 . Untested but I hope it works... r? @alexcrichton

incr.comp.: Move task result fingerprinting into DepGraph.

This PR
- makes the DepGraph store all `Fingerprints` of task results,
- allows `DepNode` to be marked as input nodes,
- makes HIR node hashing use the regular fingerprinting infrastructure,
- removes the now unused `IncrementalHashesMap`, and
- makes sure that `traits_in_scope_map` fingerprints are stable.

r? @nikomatsakis
cc @alexcrichton

Implement underscore lifetimes

Part of https://github.com/rust-lang/rust/issues/44524

Retain suid/sgid/sticky bits in Metadata.permissions

Most users would expect set_permissions(Metadata.permissions()) to be
non-destructive. While we can't guarantee this, we can at least pass
the needed info to chmod.

Also update the PermissionsExt documentation to disambiguate what it
contains, and to refer to the underlying value as `st_mode` rather than
its type `mode_t`.

Closes #44147

Catch IOError in bootstrap.py when loading config.toml

When I pulled this repo and tried to build using the command in the readme, I got an error about a missing `config.toml`.

If config.toml doesn't exist, then an `IOError` will be raised the `with open(...)` line. Prior to e788fa7b, this was caught because the `except` clause didn't specify what exceptions it caught, so both `IOError` and `OSError` were caught.

First time contributing, so please let me know if I'm doing anything wrong.

Based on ExpHP's comment in
https://users.rust-lang.org/t/refcell-borrow-mut-get-strange-result/12994

> it would perhaps be nicer if it didn't put something that could be
> misinterpreted as a valid string value

The previous Debug implementation would show:

    RefCell { value: "<borrowed>" }

The new one is:

    RefCell { value: <borrowed> }

A slight eccentricity of this change is that now non-ADT-derive errors prevent
derive-macro-not-found errors from surfacing (see changes to the
gating-of-derive compile-fail tests).

Resolves #43927.

Add iterator method .rfold(init, function); the reverse of fold

rfold is the reverse version of fold.

Fold allows iterators to implement a different (non-resumable) internal
iteration when it is more efficient than the external iteration implemented
through the next method. (Common examples are VecDeque and .chain()).

Introduce rfold() so that the same customization is available for reverse
iteration. This is achieved by both adding the method, and by having the
Rev\<I> adaptor connect Rev::rfold → I::fold and Rev::fold → I::rfold.

On the surface, rfold(..) is just .rev().fold(..), but the special case
implementations allow a data structure specific fold to be used through for
example .iter().rev(); we thus have gains even for users never calling exactly
rfold themselves.