Fix  #94192.

Rollup of 8 pull requests

Successful merges:

 - #91993 (Tweak output for non-exhaustive `match` expression)
 - #92385 (Add Result::{ok, err, and, or, unwrap_or} as const)
 - #94559 (Remove argument from closure in thread::Scope::spawn.)
 - #94580 (Emit `unused_attributes` if a level attr only has a reason)
 - #94586 (Generalize `get_nullable_type` to allow types where null is all-ones.)
 - #94708 (diagnostics: only talk about `Cargo.toml` if running under Cargo)
 - #94712 (promot debug_assert to assert)
 - #94726 (⬆ rust-analyzer)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

⬆ rust-analyzer

r? `@ghost`

promot debug_assert to assert

Fixes #94705

diagnostics: only talk about `Cargo.toml` if running under Cargo

Fixes #94646

Generalize `get_nullable_type` to allow types where null is all-ones.

Generalize get_nullable_type to accept types that have an all-ones bit
pattern as their sentry "null" value.

This will allow [`OwnedFd`], [`BorrowedFd`], [`OwnedSocket`], and
[`BorrowedSocket`] to be marked with
`#[rustc_nonnull_optimization_guaranteed]`, which will allow
`Option<OwnedFd>`, `Option<BorrowedFd>`, `Option<OwnedSocket>`, and
`Option<BorrowedSocket>` to be used in FFI declarations, as described
in the [I/O safety RFC].

For example, it will allow a function like `open` on Unix and `WSASocketW`
on Windows to be declared using `Option<OwnedFd>` and `Option<OwnedSocket>`
return types, respectively.

The actual change to add `#[rustc_nonnull_optimization_guaranteed]`
to the abovementioned types will be a separate PR, as it'll depend on
having this patch in the stage0 compiler.

Also, update the diagnostics to mention that "niche optimizations" are
used in libstd as well as libcore, as `rustc_layout_scalar_valid_range_start`
and `rustc_layout_scalar_valid_range_end` are already in use in libstd.

[`OwnedFd`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/fd/owned.rs#L49
[`BorrowedFd`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/fd/owned.rs#L29
[`OwnedSocket`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/windows/io/socket.rs#L51
[`BorrowedSocket`]: https://github.com/rust-lang/rust/blob/c9dc44be24c58ff13ce46416c4b97ab5c1bd8429/library/std/src/os/windows/io/socket.rs#L29
[I/O safety RFC]: https://github.com/rust-lang/rfcs/blob/master/text/3128-io-safety.md#ownedfd-and-borrowedfdfd-1

Emit `unused_attributes` if a level attr only has a reason

Fixes a comment from `compiler/rustc_lint/src/levels.rs`. Lint level attributes that only contain a reason will also trigger the `unused_attribute` lint. The lint now also checks for the `expect` lint level.

That's it, have a great rest of the day for everyone reasoning this 🙃

cc: #55112

Remove argument from closure in thread::Scope::spawn.

This implements ```@danielhenrymantilla's``` [suggestion](https://github.com/rust-lang/rust/issues/93203#issuecomment-1040798286) for improving the scoped threads interface.

Summary:

The `Scope` type gets an extra lifetime argument, which represents basically its own lifetime that will be used in `&'scope Scope<'scope, 'env>`:

```diff
- pub struct Scope<'env> { .. };
+ pub struct Scope<'scope, 'env: 'scope> { .. }

  pub fn scope<'env, F, T>(f: F) -> T
  where
-     F: FnOnce(&Scope<'env>) -> T;
+     F: for<'scope> FnOnce(&'scope Scope<'scope, 'env>) -> T;
```

This simplifies the `spawn` function, which now no longer passes an argument to the closure you give it, and now uses the `'scope` lifetime for everything:

```diff
-     pub fn spawn<'scope, F, T>(&'scope self, f: F) -> ScopedJoinHandle<'scope, T>
+     pub fn spawn<F, T>(&'scope self, f: F) -> ScopedJoinHandle<'scope, T>
      where
-         F: FnOnce(&Scope<'env>) -> T + Send + 'env,
+         F: FnOnce() -> T + Send + 'scope,
-         T: Send + 'env;
+         T: Send + 'scope;
```

The only difference the user will notice, is that their closure now takes no arguments anymore, even when spawning threads from spawned threads:

```diff
  thread::scope(|s| {
-     s.spawn(|_| {
+     s.spawn(|| {
          ...
      });
-     s.spawn(|s| {
+     s.spawn(|| {
          ...
-         s.spawn(|_| ...);
+         s.spawn(|| ...);
      });
  });
```

<details><summary>And, as a bonus, errors get <em>slightly</em> better because now any lifetime issues point to the outermost <code>s</code> (since there is only one <code>s</code>), rather than the innermost <code>s</code>, making it clear that the lifetime lasts for the entire <code>thread::scope</code>.

</summary>

```diff
  error[E0373]: closure may outlive the current function, but it borrows `a`, which is owned by the current function
   --> src/main.rs:9:21
    |
- 7 |         s.spawn(|s| {
-   |                  - has type `&Scope<'1>`
+ 6 |     thread::scope(|s| {
+   |                    - lifetime `'1` appears in the type of `s`
  9 |             s.spawn(|| println!("{:?}", a)); // might run after `a` is dropped
    |                     ^^                  - `a` is borrowed here
    |                     |
    |                     may outlive borrowed value `a`
    |
  note: function requires argument type to outlive `'1`
   --> src/main.rs:9:13
    |
  9 |             s.spawn(|| println!("{:?}", a)); // might run after `a` is dropped
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  help: to force the closure to take ownership of `a` (and any other referenced variables), use the `move` keyword
    |
  9 |             s.spawn(move || println!("{:?}", a)); // might run after `a` is dropped
    |                     ++++
"
```
</details>

The downside is that the signature of `scope` and `Scope` gets slightly more complex, but in most cases the user wouldn't need to write those, as they just use the argument provided by `thread::scope` without having to name its type.

Another downside is that this does not work nicely in Rust 2015 and Rust 2018, since in those editions, `s` would be captured by reference and not by copy. In those editions, the user would need to use `move ||` to capture `s` by copy. (Which is what the compiler suggests in the error.)

Add Result::{ok, err, and, or, unwrap_or} as const

Already opened tracking issue #92384.

I don't think that this should actually cause any issues as long as the constness is unstable, but we may want to double-check that this doesn't get interpreted as a weird `Drop` bound even for non-const usages.

Tweak output for non-exhaustive `match` expression

* Provide structured suggestion when missing `match` arms
* Move pointing at the missing variants *after* the main error

<img width="1164" alt="" src="https://user-images.githubusercontent.com/1606434/146312085-b57ef4a3-6e96-4f32-aa2a-803637d9eeba.png">

update Miri

Fixes https://github.com/rust-lang/rust/issues/94687
r? `@rust-lang/miri`

Try to normalize associated types before processing obligations

Closes #90729

r? `@nikomatsakis`

This makes the order of the output always consistent:

1. Place of the `match` missing arms
2. The `enum` definition span
3. The structured suggestion to add a fallthrough arm

Given

```rust
match Some(42) {
    Some(0) => {}
    Some(1) => {}
}
```

suggest

```rust
match Some(42) {
    Some(0) => {}
    Some(1) => {}
    None | Some(_) => todo!(),
}
```

Given

```rust
match Some(42) {
    Some(0) => {}
}
```

suggest

```rust
match Some(42) {
    Some(0) => {}
    None | Some(_) => todo!(),
}
```

Given

```rust
match Some(42) {}
```

suggest

```rust
match Some(42) { None | Some(_) => todo!(), }
```

Co-authored-by: NMark Rousskov <mark.simulacrum@gmail.com>

Add link to closed PR for future optimizers of ChunkedBitSet relations

While optimizing these operations proved unfruitful w.r.t. improving compiler performance right now, faster versions might be needed at a later time. This PR adds a link in the FIXME to save any future optimizers some time, as requested by `@nnethercote` in https://github.com/rust-lang/rust/pull/94625.

r? `@nnethercote`

While optimizing these operations proved unfruitful w.r.t. improving
compiler performance right now, faster versions might be needed at a
later time.

Rollup of 4 pull requests

Successful merges:

 - #93350 (libunwind: readd link attrs to _Unwind_Backtrace)
 - #93827 (Stabilize const_fn_fn_ptr_basics, const_fn_trait_bound, and const_impl_trait)
 - #94696 (Remove whitespaces and use CSS to align line numbers to the right instead)
 - #94700 (rustdoc: Update minifier version)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Fixes #94646

rustdoc: Update minifier version

This new version includes a fix for the CSS minifier which was badly handling inline media queries like ``@import` 'i';`.

r? `@notriddle`

Remove whitespaces and use CSS to align line numbers to the right instead

Instead of generating whitespaces to create padding, we simply use the CSS rule: `text-align: right`.

Nice side-effect: it reduces the generated HTML size from **75.004** to **74.828** (MegaBytes) on the std source pages (it's not much but it's always a nice plus 😆 ).

There are no changes in the generated UI.

r? `@notriddle`

Stabilize const_fn_fn_ptr_basics, const_fn_trait_bound, and const_impl_trait

# Stabilization Report

This PR serves as a request for stabilization for three const evaluation features:

1. `const_fn_fn_ptr_basics`
2. `const_fn_trait_bound`
3. `const_impl_trait`

These are being stabilized together because they are relatively minor and related updates to existing functionality.

## `const_fn_fn_ptr_basics`

Allows creating, passing, and casting function pointers in a `const fn`.

The following is an example of what is now allowed:

```rust
const fn get_function() -> fn() {
    fn foo() {
        println!("Hello, World!");
    }

    foo
}
```

Casts between function pointer types are allowed, as well as transmuting from integers:

```rust
const fn get_function() -> fn() {
    unsafe {
        std::mem::transmute(0x1234usize)
    }
}
```

However, casting from a function pointer to an integer is not allowed:

```rust
const fn fn_to_usize(f: fn()) -> usize {
    f as usize  //~ pointers cannot be cast to integers during const eval
}
```

Calling function pointers is also not allowed.

```rust
const fn call_fn_ptr(f: fn()) {
    f() //~ function pointers are not allowed in const fn
}
```

### Test Coverage

The following tests include code that exercises this feature:

- `src/test/ui/consts/issue-37550.rs`
- `src/test/ui/consts/issue-46553.rs`
- `src/test/ui/consts/issue-56164.rs`
- `src/test/ui/consts/min_const_fn/allow_const_fn_ptr_run_pass.rs`
- `src/test/ui/consts/min_const_fn/cast_fn.rs`
- `src/test/ui/consts/min_const_fn/cmp_fn_pointers.rs`

## `const_fn_trait_bound`

Allows trait bounds in `const fn`. Additionally, this feature allows creating and passing `dyn Trait` objects.

Examples such as the following are allowed by this feature:

```rust
const fn do_thing<T: Foo>(_x: &T) {
    // ...
}
```

Previously only `Sized` was allowed as a trait bound.

There is no way to call methods from the trait because trait methods cannot currently be marked as const. Allowing trait bounds in const functions does allow the const function to use the trait's associated types and constants.

This feature also allowes `dyn Trait` types. These work equivalently to non-const code. Similar to other pointers in const code, the value of a `dyn Trait` pointer cannot be observed.

Note that due to https://github.com/rust-lang/rust/issues/90912, it was already possible to do the example above as follows:

```rust
const fn do_thing<T>(_x: &T) where (T,): Foo {
    // ...
}
```

### Test Coverage

The following tests include code that exercises `const_fn_trait_bound`:

- `src/test/ui/consts/const-fn.rs`
- `src/test/ui/consts/issue-88071.rs`
- `src/test/ui/consts/min_const_fn/min_const_fn.rs`
- `src/test/ui/consts/min_const_fn/min_const_fn_dyn.rs`
- `src/test/ui/nll/issue-55825-const-fn.rs`
- Many of the tests in `src/test/ui/rfc-2632-const-trait-impl/` also exercise this feature.

## `const_impl_trait`

Allows argument and return position `impl Trait` in a `const fn`, such as in the following example:

```rust
const fn do_thing(x: impl Foo) -> impl Foo {
    x
}
```

Similar to generic parameters and function pointers, this allows the creation of such opaque types, but not doing anything with them beyond accessing associated types and constants.

### Test Coverage

The following tests exercise this feature:

- `src/test/ui/type-alias-impl-trait/issue-53096.rs`
- `src/test/ui/type-alias-impl-trait/issue-53678-generator-and-const-fn.rs`

## Documentation

These features are documented along with the other const evaluation features in the Rust Reference at https://doc.rust-lang.org/stable/reference/const_eval.html.

There is a PR that updates this documentation to reflect the capabilities enabled by these features at https://github.com/rust-lang/reference/pull/1166.

Tracking issues: #57563, #63997, #93706

libunwind: readd link attrs to _Unwind_Backtrace

It seems the removal of these in 1c07096a was unintended; readding them fixes the build.

fixes rust-lang/rust#93349

r? `@alexcrichton`

Clarify `Layout` interning.

`Layout` is another type that is sometimes interned, sometimes not, and
we always use references to refer to it so we can't take any advantage
of the uniqueness properties for hashing or equality checks.

This commit renames `Layout` as `LayoutS`, and then introduces a new
`Layout` that is a newtype around an `Interned<LayoutS>`. It also
interns more layouts than before. Previously layouts within layouts
(via the `variants` field) were never interned, but now they are. Hence
the lifetime on the new `Layout` type.

Unlike other interned types, these ones are in `rustc_target` instead of
`rustc_middle`. This reflects the existing structure of the code, which
does layout-specific stuff in `rustc_target` while `TyAndLayout` is
generic over the `Ty`, allowing the type-specific stuff to occur in
`rustc_middle`.

The commit also adds a `HashStable` impl for `Interned`, which was
needed. It hashes the contents, unlike the `Hash` impl which hashes the
pointer.

r? `@fee1-dead`