For now, this pass does some easy transformations, like eliminating
empty blocks that just jump to another block, some trivial
conversion of If terminators into Gotos and removal of dead blocks.

r? @nikomatsakis

For now, this pass does some easy transformations, like eliminating
empty blocks that just jump to another block, some trivial
conversion of If terminators into Gotos and removal of dead blocks.

Did this alphabetically, so I didn't see [how `std` was doing things](https://dxr.mozilla.org/rust/source/src/libstd/lib.rs#215) till I was nearly finished. If you prefer to add crate-level-whitelists like std instead of test-level, I can rebase with that strategy.

A number of these commits can probably be dropped as the crates don't have much to test, and are deprecated. Let me know which if any to drop! (can also squash after review if desired)

r? @steveklabnik

`format_args!` doesn't support none Sized types so we should just pass it the references to `left_val` and `right_val`.

The following works:
```rust
assert!([1, 2, 3][..] == vec![1, 2, 3][..])
```
So I would expect this to as well:
```rust
assert_eq!([1, 2, 3][..], vec![1, 2, 3][..])
```
But it fails with "error: the trait `core::marker::Sized` is not implemented for the type `[_]` [E0277]"
I don't know if this change will have any nasty side effects I don't understand.

- Successful merges: #29776, #29785, #29786, #29787
- Failed merges:

Fix usage of wrong article in `Result` docs.

This is my first rust PR, if something about the process is wrong let me know.

As this is a documentation change, I believe the correct highfive line to use is the following:

r? @steveklabnik

This mostly brings them in line with existing linking convention, but
also has some minor re-wording.

The text at the top has been re-focused, by starting out with what the
prelude does, rather than starting from injecting std.

Also, it now mentions that other preludes exist.

Part of https://github.com/rust-lang/rust/issues/29369

In previous PRs, I changed the match desugaring to generate more efficient code for ints/chars and the like. But this doesn't help when you're matching strings, ranges, or other crazy complex things (leading to #29740). This commit restructures match desugaring *yet again* to handle that case better -- basically we now degenerate to an if-else-if chain in such cases.

~~Note that this builds on https://github.com/rust-lang/rust/pull/29763 which will hopefully land soon. So ignore the first few commits.~~ landed now

r? @Aatch since he's been reviewing the other commits in this series

Emits loc, and node count - before and after expansion.

E.g.,

```
rustc: x86_64-unknown-linux-gnu/stage2/lib/rustlib/x86_64-unknown-linux-gnu/lib/libcore
Lines of code:             32060
Pre-expansion node count:  120205
Post-expansion node count: 482749
```

r? @nikomatsakis

r? @nikomatsakis

I went ahead and replaced repeat count with a `Constant`, because it cannot be non-constant to the best of my knowledge.

bothered to track down for a regresson test. /me hopes no one notices

Closes https://github.com/rust-lang/rust/issues/29746

This mostly brings them in line with existing linking convention, but
also has some minor re-wording.

The text at the top has been re-focused, by starting out with what the
prelude does, rather than starting from injecting std.

Also, it now mentions that other preludes exist.

Part of https://github.com/rust-lang/rust/issues/29369

large matches that fallback to Eq. When we encounter a case where the
test being performed does not inform the candidate at all, we just stop
testing the candidates at that point, rather than adding the candidate
to both outcomes. The former behavior was not WRONG, but it generated a
lot of code, whereas this new behavior degenerates to an if-else-if
tree.

Fixes #29740.

- Successful merges: #29677, #29772, #29775, #29777
- Failed merges: