Size has a ::zero

Don't special case the `Self` parameter by name

This results in a couple of small diagnostic regressions. They could be avoided by keeping the special case just for diagnostics, but that seems worse.

closes #50125
cc #60869

Change the placement of two functions.

Right now, the order is as follows:
`pop_front()`
`push_front()`
`push_back()`
`pop_back()`

`swap_remove_back()`
`swap_remove_front()`

I believe it would be more natural, and easier to follow, if we place `pop_back()` right after the `pop_front()`, and `swap_remove_back()` after the `swap_remove_front()` like this:
`pop_front()`
`pop_back()`
`push_front()`
`push_back()`

`swap_remove_front()`
`swap_remove_back()`

The rest of the documentation (at least in this module) adheres to the same logic, where the 'front' function always precedes its 'back' equivalent.

Use this to simplify the object safety code a bit.

Improved error message for break in async block

Fixes #63391

Do not generate allocations for zero sized allocations

Alternative to https://github.com/rust-lang/rust/issues/62487

r? @EddyB

There are other places where we could do this, too, but that would cause `static FOO: () = ();` to not have a unique address

Serialize additional data for procedural macros

Split off from #62855

This PR serializes the declaration `Span` and attributes for all
procedural macros. This allows Rustdoc to properly render doc comments
and source links when performing inlinig procedural macros across crates

Normalize newlines when loading files

Fixes #62865

Initial implementation of or-patterns

An incomplete implementation of or-patterns (e.g. `Some(0 | 1)` as a pattern). This patch set aims to implement initial parsing of `or-patterns`.

Related to: #54883

CC @alexreg @varkor
r? @Centril

Rollup of 5 pull requests

Successful merges:

 - #62451 (Add APIs for uninitialized Box, Rc, and Arc. (Plus get_mut_unchecked))
 - #63487 (Remove meaningless comments in src/test)
 - #63657 (Crank up invalid value lint)
 - #63667 (resolve: Properly integrate derives and `macro_rules` scopes)
 - #63669 (fix typos in mir/interpret)

Failed merges:

r? @ghost

fix typos in mir/interpret

resolve: Properly integrate derives and `macro_rules` scopes

So,
```rust
#[derive(A, B)]
struct S;

m!();
```
turns into something like
```rust
struct S;

A_placeholder!( struct S; );

B_placeholder!( struct S; );

m!();
```
during expansion.

And for `m!()` its "`macro_rules` scope" (aka "legacy scope") should point to the `B_placeholder` call rather than to the derive container `#[derive(A, B)]`.

`fn build_reduced_graph` now makes sure the legacy scope points to the right thing.
(It's still a mystery for me why this worked before https://github.com/rust-lang/rust/pull/63535.)

Unfortunately, placeholders from derives are currently treated separately from placeholders from other macros and need to be passed as `extra_placeholders` rather than a part of the AST fragment.
That's fixable, but I wanted to keep this PR more minimal to close the regression faster.

Fixes https://github.com/rust-lang/rust/issues/63651
r? @matthewjasper

Crank up invalid value lint

* Warn against uninit `bool` and `char`.
* Warn against 0-init `NonNull` and friends
* Detect transmute-from-0 as zero-initialization ([seen in the wild](https://github.com/glium/glium/issues/1775#issuecomment-522144636))

Remove meaningless comments in src/test

Moved from #63411

Add APIs for uninitialized Box, Rc, and Arc. (Plus get_mut_unchecked)

Assigning `MaybeUninit::<Foo>::uninit()` to a local variable is usually free, even when `size_of::<Foo>()` is large. However, passing it for example to `Arc::new` [causes at least one copy](https://youtu.be/F1AquroPfcI?t=4116) (from the stack to the newly allocated heap memory) even though there is no meaningful data. It is theoretically possible that a Sufficiently Advanced Compiler could optimize this copy away, but this is [reportedly unlikely to happen soon in LLVM](https://youtu.be/F1AquroPfcI?t=5431).

This PR proposes two sets of features:

* Constructors for containers (`Box`, `Rc`, `Arc`) of `MaybeUninit<T>` or `[MaybeUninit<T>]` that do not initialized the data, and unsafe conversions to the known-initialized types (without `MaybeUninit`). The constructors are guaranteed not to make unnecessary copies.

* On `Rc` and `Arc`, an unsafe `get_mut_unchecked` method that provides `&mut T` access without checking the reference count. `Arc::get_mut` involves multiple atomic operations whose cost can be non-trivial. `Rc::get_mut` is less costly, but we add `Rc::get_mut_unchecked` anyway for symmetry with `Arc`.

  These can be useful independently, but they will presumably be typical when the new constructors of `Rc` and `Arc` are used.

  An alternative with a safe API would be to introduce `UniqueRc` and `UniqueArc` types that have the same memory layout as `Rc` and `Arc` (and so zero-cost conversion to them) but are guaranteed to have only one reference. But introducing entire new types feels “heavier” than new constructors on existing types, and initialization of `MaybeUninit<T>` typically requires unsafe code anyway.

Summary of new APIs (all unstable in this PR):

```rust
impl<T> Box<T> { pub fn new_uninit() -> Box<MaybeUninit<T>> {…} }
impl<T> Box<MaybeUninit<T>> { pub unsafe fn assume_init(self) -> Box<T> {…} }
impl<T> Box<[T]> { pub fn new_uninit_slice(len: usize) -> Box<[MaybeUninit<T>]> {…} }
impl<T> Box<[MaybeUninit<T>]> { pub unsafe fn assume_init(self) -> Box<[T]> {…} }

impl<T> Rc<T> { pub fn new_uninit() -> Rc<MaybeUninit<T>> {…} }
impl<T> Rc<MaybeUninit<T>> { pub unsafe fn assume_init(self) -> Rc<T> {…} }
impl<T> Rc<[T]> { pub fn new_uninit_slice(len: usize) -> Rc<[MaybeUninit<T>]> {…} }
impl<T> Rc<[MaybeUninit<T>]> { pub unsafe fn assume_init(self) -> Rc<[T]> {…} }

impl<T> Arc<T> { pub fn new_uninit() -> Arc<MaybeUninit<T>> {…} }
impl<T> Arc<MaybeUninit<T>> { pub unsafe fn assume_init(self) -> Arc<T> {…} }
impl<T> Arc<[T]> { pub fn new_uninit_slice(len: usize) -> Arc<[MaybeUninit<T>]> {…} }
impl<T> Arc<[MaybeUninit<T>]> { pub unsafe fn assume_init(self) -> Arc<[T]> {…} }

impl<T: ?Sized> Rc<T> { pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {…} }
impl<T: ?Sized> Arc<T> { pub unsafe fn get_mut_unchecked(this: &mut Self) -> &mut T {…} }
```

Co-Authored-By: NRalf Jung <post@ralfj.de>

Refactor Miri ops (unary, binary) to have more types

This is the part of https://github.com/rust-lang/rust/pull/63448 that is just a refactoring. It helps that PR by making it easier to perform machine arithmetic.

r? @oli-obk @EddyB

Split off from #62855

This PR deerializes the declaration `Span` and attributes for all
procedural macros from their underlying function definitions.
This allows Rustdoc to properly render doc comments
and source links when inlining procedural macros across crates

Initial implementation of parsing or-patterns e.g., `Some(Foo | Bar)`.
This is a partial implementation of RFC 2535.

Co-Authored-By: NRalf Jung <post@ralfj.de>

Opaque builtin derive macros

* Buiilt-in derives are now opaque macros
    * This required limiting the visibility of some previously unexposed functions in `core`.
    * This also required the change to `Ident` serialization.
* All gensyms are replaced with hygienic identifiers
* Use hygiene to avoid most other name-resolution issues with buiilt-in derives.
    *  As far as I know the only remaining case that breaks is an ADT that has the same name as one of its parameters. Fixing this completely seemed to be more effort than it's worth.
* Remove gensym in `Ident::decode`, which lead to linker errors due to `inline` being gensymmed.
    * `Ident`now panics if incremental compilation tries to serialize it (it currently doesn't).
    * `Ident` no longer uses `gensym` to emulate cross-crate hygiene. It only applied to reexports.
    * `SyntaxContext` is no longer serializable.
    * The long-term fix for this is to properly implement cross-crate hygiene, but this seemed to be acceptable for now.
* Move type/const parameter shadowing checks to `resolve`
    * This was previously split between resolve and type checking. The type checking pass compared `InternedString`s, not Identifiers.
* Removed the `SyntaxContext` from `{ast, hir}::{InlineAsm, GlobalAsm}`

cc #60869
r? @petrochenkov

Co-Authored-By: NMazdak Farrokhzad <twingoow@gmail.com>