Carrier trait (third attempt)
This adds a `Carrier` trait to operate with `?`. The only public implementation is for `Result`, so effectively the trait does not exist, however, it ensures future compatibility for the `?` operator. This is not intended to be used, nor is it intended to be a long-term solution.
Although this exact PR has not been through Crater, I do not expect it to be a breaking change based on putting numerous similar PRs though Crater in the past.
cc:
* [? tracking issue](https://github.com/rust-lang/rust/issues/31436)
* [previous PR](https://github.com/rust-lang/rust/pull/35056)
* [RFC issue](https://github.com/rust-lang/rfcs/issues/1718) for discussion of long-term Carrier trait solutions.
r? @nikomatsakis
Based on following what happens in CString::new("string literal"):
1. Using `Into<Vec<u8>>`, a Vec is allocated with capacity exactly equal
to the string's input length.
2. By `v.push(0)`, the Vec is grown to twice capacity, since it was full.
3. By `v.into_boxed_slice()`, the Vec capacity is shrunk to fit the length again.
If we use `.reserve_exact(1)` just before the push, then we avoid the
capacity doubling that we're going to have to shrink anyway.
Growing by just 1 byte means that the step (2) is less likely to have to
move the memory to a larger allocation chunk, and that the step (3) does
not have to reallocate.
Experimentally, this fixes the poor re-use observed in
libsyntex-syntax. I'm not sure how to make a regression test for this,
though, given the non-deterministic nature of it.
Wording fixes in error messages
This PR is largely wording fixes to existing PRs that I found going back through the ones that have already been updated. Sometimes seeing the message in context made me think "oh there's a better wording!"
There's one additional fix. This will also prevent the secondary underlining of derive call (since they look like macros to the system in the way I was using):
```
error[E0184]: the trait `Copy` may not be implemented for this type; the type has a destructor
--> src/test/compile-fail/E0184.rs:11:10
|
11 | #[derive(Copy)] //~ ERROR E0184
| ^^^^
| |
| in this macro invocation
```
Is now just:
```
error[E0184]: the trait `Copy` may not be implemented for this type; the type has a destructor
--> src/test/compile-fail/E0184.rs:11:10
|
11 | #[derive(Copy)] //~ ERROR E0184
| ^^^^
```
Add workaround to detect correct compiler version
This adds a workaround which fixes a rustbuild issue where the wrong compiler is checked for the version number. The bug would arise if you build the system correctly then changed to any other version (eg doing a `git pull`). After changing to the new version, building would fail and complain that crates were built with the wrong compiler.
There are actually two compilers at play, the bootstrapping compiler (called the "snapshot" compiler) and the actual compiler being built (the "real" compiler). In the case of this issue, the wrong compiler was being checked for version mismatch.
r? @alexcrichton
replace `Add` example with something more evocative of addition
Currently most of the operator traits use trivial implementation
examples that only perform side effects. Honestly, that might not be too
bad for the sake of documentation; but anyway, here's a proposal to move
a slightly modified version of the module-level point-addition example
into the `Add` documentation, since it's more evocative of addition
semantics.
Part of #29365
rustdoc: remove the `!` from macro URLs and titles
Because the `!` is part of a macro use, not the macro's name. E.g., you write `macro_rules! foo` not `macro_rules! foo!`, also `#[macro_import(foo)]`.
(Pulled out of #35020).
This avoids the compile-time overhead of computing them twice. It also fixes
an issue where the hash computed after typeck is differen than the hash before,
because typeck mutates the def-map in place.
Fixes#35549.
Fixes#35593.
