Avoid prematurely recording toolstates

When we're running with dry_run enabled (i.e. all builds do this initially), we're
guaranteed to save of a toolstate of TestFail for tools that aren't tested. In practice,
we do test tools as well, so for those tools we would initially record them as being
TestPass, and then later on re-record the correct state after actually testing them.
However, this would not work well if the build failed for whatever reason (e.g. panicking
in bootstrap, or as was the case in #73097, clippy failing to test successfully), we would
just go on believing that things passed when they in practice did not.

This commit also adjusts saving toolstate to never record clippy explicitly (otherwise, it
would be recorded when building it); eventually that'll likely move to other tools as well
but not yet. This is deemed simpler than checking everywhere we generically save
toolstate.

We also move clippy out of the "toolstate" no-fail-fast build into a separate x.py
invocation; this should no longer be technically required but provides the nice state of
letting us check toolstate for all tools and only then check clippy (giving full results
on every build).

r? @oli-obk

Supercedes #73275, also fixes #73274

store `ObligationCause` on the heap

Stores `ObligationCause` on the heap using an `Rc`.

This PR trades off some transient memory allocations to reduce the size of–and thus the number of instructions required to memcpy–a few widely used data structures in trait solving.

When we're running with dry_run enabled (i.e. all builds do this initially), we're
guaranteed to save of a toolstate of TestFail for tools that aren't tested. In practice,
we do test tools as well, so for those tools we would initially record them as being
TestPass, and then later on re-record the correct state after actually testing them.
However, this would not work well if the build failed for whatever reason (e.g. panicking
in bootstrap, or as was the case in 73097, clippy failing to test successfully), we would
just go on believing that things passed when they in practice did not.

This commit also adjusts saving toolstate to never record clippy explicitly (otherwise, it
would be recorded when building it); eventually that'll likely move to other tools as well
but not yet. This is deemed simpler than checking everywhere we generically save
toolstate.

We also move clippy out of the "toolstate" no-fail-fast build into a separate x.py
invocation; this should no longer be technically required but provides the nice state of
letting us check toolstate for all tools and only then check clippy (giving full results
on every build).

Implement new gdb/lldb pretty-printers

Reopened #60826

This PR replaces current gdb and lldb pretty-printers with new ones that were originally written for [IntelliJ Rust](https://github.com/intellij-rust/intellij-rust/tree/master/prettyPrinters).

The current state of lldb pretty-printers is poor, because [they don't use synthetic children](https://github.com/rust-lang/rust/issues/55586#issuecomment-436610063). When I started to reimplement lldb pretty-printers with synthetic children support, I've found current version strange and hard to support. I think `debugger_pretty_printers_common.py` is overkill, so I got rid of it.

The new pretty-printers have to support all types supported by current pretty-printers, and also support `Rc`, `Arc`, `Cell`, `Ref`, `RefCell`, `RefMut`, `HashMap`, `HashSet`.

Fixes #56252

Rollup of 10 pull requests

Successful merges:

 - #72707 (Use min_specialization in the remaining rustc crates)
 - #72740 (On recursive ADT, provide indirection structured suggestion)
 - #72879 (Miri: avoid tracking current location three times)
 - #72938 (Stabilize Option::zip)
 - #73086 (Rename "cyclone" to "apple-a7" per changes in upstream LLVM)
 - #73104 (Example about explicit mutex dropping)
 - #73139 (Add methods to go from a nul-terminated Vec<u8> to a CString)
 - #73296 (Remove vestigial CI job msvc-aux.)
 - #73304 (Revert heterogeneous SocketAddr PartialEq impls)
 - #73331 (extend network support for HermitCore)

Failed merges:

r? @ghost

extend network support for HermitCore

- add basic support of TcpListerner for HermitCore
- revise TcpStream to support peer_addr

Revert heterogeneous SocketAddr PartialEq impls

Originally added in #72239.

These lead to inference regressions (mostly in tests) in code that looks like:

```rust
let socket = SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), 8080);
assert_eq!(socket, "127.0.0.1:8080".parse().unwrap());
```

That compiles as of stable 1.44.0 but fails in beta with:

```console
error[E0284]: type annotations needed
 --> src/main.rs:3:41
  |
3 |     assert_eq!(socket, "127.0.0.1:8080".parse().unwrap());
  |                                         ^^^^^ cannot infer type for type parameter `F` declared on the associated function `parse`
  |
  = note: cannot satisfy `<_ as std::str::FromStr>::Err == _`
help: consider specifying the type argument in the method call
  |
3 |     assert_eq!(socket, "127.0.0.1:8080".parse::<F>().unwrap());
  |
```

Closes #73242.

Remove vestigial CI job msvc-aux.

This CI job isn't really doing anything, so it seems prudent to remove it.

For some history:
* This was introduced in #48809 when the msvc job was split in two to keep it under 2 hours (oh the good old days). At the time, this check-aux job did a bunch of things:
    * tidy
    * src/test/pretty
    * src/test/run-pass/pretty
    * src/test/run-fail/pretty
    * src/test/run-pass-valgrind/pretty
    * src/test/run-pass-fulldeps/pretty
    * src/test/run-fail-fulldeps/pretty
* Tidy was removed in #60777.
* run-pass and run-pass-fulldeps moved to UI in #63029
* src/test/pretty removed in #58140
* src/test/run-fail moved to UI in #71185
* run-fail-fulldeps removed in #51285

Over time through attrition, the job was left with one lonely thing: `src/test/run-pass-valgrind/pretty`. And of course, this wasn't actually running the "pretty" tests. The normal `run-pass-valgrind` tests ran, and then when it tried to run in "pretty" mode, all the tests were ignored because compiletest thought nothing had changed (apparently compiletest isn't fingerprinting the mode?  Needs more investigation…). `run-pass-valgrind` is already being run as part of `x86_64-msvc-1`, so there's no need to run it here.

I've taken the liberty of removing `src/test/run-pass-valgrind/pretty` as a distinct test. I'm guessing from the other PR's that the pretty tests should now live in `src/test/pretty`, and that the team has moved away from doing pretty tests on other parts of the `src/test` tree.

Add methods to go from a nul-terminated Vec<u8> to a CString

Fixes #73100.

Doc tests have been written and the documentation on the error type
updated too.

I used `#[stable(feature = "cstring_from_vec_with_nul", since = "1.46.0")]` but I don't know if the version is correct.

Example about explicit mutex dropping

Fixes #67457.

Following the remarks made in #73074, I added an example on the main `Mutex` type, with a situation where there is mutable data and a computation result.

In my testing it is effectively needed to explicitly drop the lock, else it deadlocks.

r? @dtolnay because you were the one to review the previous PR.

Rename "cyclone" to "apple-a7" per changes in upstream LLVM

It looks like they intended to keep "cyclone" as a legacy option, but removed it from the list of subtarget features. This created a flood of warnings when targeting aarch64-apple-ios, and probably also created incorrectly optimized artifacts.

See:
https://reviews.llvm.org/D70779
https://reviews.llvm.org/D70779#C1703593NL568

LLVM 10 merged into master at:
https://github.com/rust-lang/rust/pull/67759

Stabilize Option::zip

This PR stabilizes the following API:

```rust
impl<T> Option<T> {
    pub fn zip<U>(self, other: Option<U>) -> Option<(T, U)>;
}
```

This API has real world usage as seen in <https://grep.app/search?q=-%3E%20Option%3C%5C%28T%2C%5Cs%3FU%5C%29%3E&regexp=true&filter[lang][0]=Rust>.

The `zip_with` method is left unstably as this API is kinda niche
and it hasn't received much usage in Rust repositories on GitHub.

cc #70086

Miri: avoid tracking current location three times

Miri tracks the current instruction to execute in the call stack, but it also additionally has two `TyCtxtAt` that carry a `Span` that also tracks the current instruction. That is quite silly, so this PR uses `TyCtxt` instead, and then uses a method for computing the current span when a `TyCtxtAt` is needed. Having less redundant (semi-)global state seems like a good improvement to me. :D

To keep the ConstProp errors the same, I had to add the option to `error_to_const_error` to overwrite the span. Also for some reason this changes cycle errors a bit -- not sure if we are now better or worse as giving those queries the right span. (It is unfortunately quite easy to accidentally use `DUMMY_SP` by calling the query on a `TyCtxt` instead of a `TyCtxtAt`.)

r? @oli-obk @EddyB

On recursive ADT, provide indirection structured suggestion

Use min_specialization in the remaining rustc crates

This adds a lot of `transmute` calls to replace the unsound uses of specialization.
It's ugly, but at least it's honest about what's going on.

cc #71420, @RalfJung

Rollup of 10 pull requests

Successful merges:

 - #71824 (Check for live drops in constants after drop elaboration)
 - #72389 (Explain move errors that occur due to method calls involving `self`)
 - #72556 (Fix trait alias inherent impl resolution)
 - #72584 (Stabilize vec::Drain::as_slice)
 - #72598 (Display information about captured variable in `FnMut` error)
 - #73336 (Group `Pattern::strip_*` method together)
 - #73341 (_match.rs: fix module doc comment)
 - #73342 (Fix iterator copied() documentation example code)
 - #73351 (Update E0446.md)
 - #73353 (structural_match: non-structural-match ty closures)

Failed merges:

r? @ghost

structural_match: non-structural-match ty closures

Fixes #73003.

This PR adds a `Closure` variant to `NonStructuralMatchTy` in `structural_match`, fixing an ICE which can occur when `impl_trait_in_bindings` is used with constants.

Update E0446.md

The existing error documentation did not show how to use a child module's functions if the types used in those functions are private. These are some other places this problem has popped up that did not present a solution (these are from before the solution existed, 2016-2017. The solution was released in the Rust 2018 edition. However these were the places I was pointed to when I encountered the problem myself):
https://github.com/rust-lang/rust/issues/30905
https://stackoverflow.com/questions/39334430/how-to-reference-private-types-from-public-functions-in-private-modules/62374958#62374958

Fix iterator copied() documentation example code

The documentation for copied() gives example code with variable v_cloned instead of v_copied. This seems like a copy/paste error from cloned() and it would be clearer to use v_copied.

_match.rs: fix module doc comment

It was applied to a `use` item, not to the module

Group `Pattern::strip_*` method together

Display information about captured variable in `FnMut` error

Fixes #69446

When we encounter a region error involving an `FnMut` closure, we
display a specialized error message. However, we currently do not
tell the user which upvar was captured. This makes it difficult to
determine the cause of the error, especially when the closure is large.

This commit records marks constraints involving closure upvars
with `ConstraintCategory::ClosureUpvar`. When we decide to 'blame'
a `ConstraintCategory::Return`, we additionall store
the captured upvar if we found a `ConstraintCategory::ClosureUpvar` in
the path.

When generating an error message, we point to relevant spans if we have
closure upvar information available. We further customize the message if
an `async` closure is being returned, to make it clear that the captured
variable is being returned indirectly.

Stabilize vec::Drain::as_slice

and add `AsRef<[T]> for Drain<'_, T>`.

Tracking issue: #58957. Does not stabilize `slice::IterMut::as_slice` yet. cc @cuviper
This PR proposes stabilizing just the `vec::Drain::as_slice` part of that tracking issue.

My ultimate goal here: being able to use `for<T, I: Iterator<Item=T> + AsRef<[T]>> I` to refer to `vec::IntoIter`, `vec::Drain`, and eventually `array::IntoIter`, as an approximation of the set of by-value iterators that can be "previewed" as by-ref iterators. (Actually expressing that as a trait requires GAT.)

Fix trait alias inherent impl resolution

Fixes #60021 and fixes #72415.

Obviously, the fix was very easy, but getting started with the testing and debugging rust compiler was an interesting experience. Now I can cross it off my bucket list!

Explain move errors that occur due to method calls involving `self`

When calling a method that takes `self` (e.g. `vec.into_iter()`), the method receiver is moved out of. If the method receiver is used again, a move error will be emitted::

```rust
fn main() {
    let a = vec![true];
    a.into_iter();
    a;
}
```

emits

```
error[E0382]: use of moved value: `a`
 --> src/main.rs:4:5
  |
2 |     let a = vec![true];
  |         - move occurs because `a` has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait
3 |     a.into_iter();
  |     - value moved here
4 |     a;
  |     ^ value used here after move
```

However, the error message doesn't make it clear that the move is caused by the call to `into_iter`.

This PR adds additional messages to move errors when the move is caused by using a value as the receiver of a `self` method::

```
error[E0382]: use of moved value: `a`
   --> vec.rs:4:5
    |
2   |     let a = vec![true];
    |         - move occurs because `a` has type `std::vec::Vec<bool>`, which does not implement the `Copy` trait
3   |     a.into_iter();
    |     ------------- value moved due to this method call
4   |     a;
    |     ^ value used here after move
    |
note: this function takes `self`, which moves the receiver
   --> /home/aaron/repos/rust/src/libcore/iter/traits/collect.rs:239:5
    |
239 |     fn into_iter(self) -> Self::IntoIter;
```

TODO:

- [x] Add special handling for `FnOnce/FnMut/Fn` - we probably don't want to point at the unstable trait methods
- [x] Consider adding additional context for operations (e.g. `Shr::shr`) when the call was generated using the operator syntax (e.g. `a >> b`)
- [x] Consider pointing to the method parent (impl or trait block) in addition to the method itself.

Check for live drops in constants after drop elaboration

Resolves #66753.

This PR splits the MIR "optimization" pass series in two and introduces a query–`mir_drops_elaborated_and_const_checked`–that holds the result of the `post_borrowck_cleanup` analyses and checks for live drops. This query is invoked in `rustc_interface` for all items requiring const-checking, which means we now do `post_borrowck_cleanup` for items even if they are unused in the crate.

As a result, we are now more precise about when drops are live. This is because drop elaboration can e.g. eliminate drops of a local when all its fields are moved from. This does not mean we are doing value-based analysis on move paths, however; Storing a `Some(CustomDropImpl)` into a field of a local will still set the qualifs for that entire local.

r? @oli-obk

This reverts commit d221ffc6.

This reverts commit 9d596b50.

Clean up type alias impl trait implementation

- Removes special case for top-level impl trait
- Removes associated opaque types
- Forbid lifetime elision in let position impl trait. This is consistent with the behavior for inferred types.
- Handle lifetimes in type alias impl trait more uniformly with other parameters

cc #69323
cc #63063
Closes #57188
Closes #62988
Closes #69136
Closes #73061

The existing error documentation did not show how to use a child module's functions if the types used in those functions are private. These are some other places this problem has popped up that did not present a solution (these are from before the solution existed, 2016-2017. The solution was released in the Rust 2018 edition. However these were the places I was pointed to when I encountered the problem myself):
https://github.com/rust-lang/rust/issues/30905
https://stackoverflow.com/questions/39334430/how-to-reference-private-types-from-public-functions-in-private-modules/62374958#62374958

This commit adds a `Closure` variant to `NonStructuralMatchTy` in
`structural_match`, fixing an ICE which can occur when
`impl_trait_in_bindings` is used with constants.
Signed-off-by: NDavid Wood <david@davidtw.co>