Document default values for primitive types
All primitive types implement the `Default` trait but the documentation just says `Returns the "default value" for a type.` and doesn't give a hint about the actual default value. I think it would be good to document the default values in a proper way.
I changed the `default_impl` macro to accept a doc string as a third parameter and use this string to overwrite the documentation of `default()` for each primitive type.
The generated documentation now looks like this:
Disable big-endian simd in swap_nonoverlapping_bytes
This is a workaround for #42778, which was git-bisected to #40454's
optimizations to `mem::swap`, later moved to `ptr` in #42819. Natively
compiled rustc couldn't even compile stage1 libcore on powerpc64 and
s390x, but they work fine without this `repr(simd)`. Since powerpc64le
works OK, it seems probably related to being big-endian.
The underlying problem is not yet known, but this at least makes those
architectures functional again in the meantime.
cc @arielb1
Implement Eq/Hash/Debug etc. for unsized tuples.
As I mentioned in [the comment in #18469](https://github.com/rust-lang/rust/issues/18469#issuecomment-306767422), the implementations of `PartialEq`, `Eq`, `PartialOrd`, `Ord`, `Debug`, `Hash` can be generalized to unsized tuples.
This is consistent with the `derive` behavior for unsized structs.
```rust
#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Debug, Default, Hash)]
struct MyTuple<X, Y, Z: ?Sized>(X, Y, Z);
fn f(x: &MyTuple<i32, i32, [i32]>) {
x == x;
x < x;
println!("{:?}", x);
}
```
Questions:
- Need an RFC?
- Need a feature gate? I don't think it does because the unsized tuple coercion #42527 is feature-gated.
- I changed `builder.field($name);` into `builder.field(&$name);` in the `Debug` implementation to pass compilation. This won't affect the behavior because `Debug for &'a T` is a mere redirection to `Debug for T`. However, I don't know if it affects code size / performance.
This is a workaround for #42778, which was git-bisected to #40454's
optimizations to `mem::swap`, later moved to `ptr` in #42819. Natively
compiled rustc couldn't even compile stage1 libcore on powerpc64 and
s390x, but they work fine without this `repr(simd)`. Since powerpc64le
works OK, it seems probably related to being big-endian.
The underlying problem is not yet known, but this at least makes those
architectures functional again in the meantime.
cc @arielb1
Update docs for Debug* structs. #29355
This adds docs for the Debug* structs as well as examples from the
Formatter::debug_* methods, so that a user knows how to construct them.
I added these examples as the builders module is not public and hence
the debug_*_new() functions are not available to a user.
r? @steveklabnik
Delete deprecated & unstable range-specific `step_by`
Using the new one is annoying while this one exists, since the inherent method hides the one on iterator.
Tracking issue: #27741
Replacement: #41439
Deprecation: #42310 for 1.19
Fixes#41477
This adds docs for the Debug* structs as well as examples from the
Formatter::debug_* methods, so that a user knows how to construct them.
I added these examples as the builders module is not public and hence
the debug_*_new() functions are not available to a user.
r? @steveklabnik
Review comments.
Mainly adding in the links for all of the structs and functions.
Remove rust tag on code blocks.
Add `Iterator::for_each`
This works like a `for` loop in functional style, applying a closure to
every item in the `Iterator`. It doesn't allow `break`/`continue` like
a `for` loop, nor any other control flow outside the closure, but it may
be a more legible style for tying up the end of a long iterator chain.
This was tried before in #14911, but nobody made the case for using it
with longer iterators. There was also `Iterator::advance` at that time
which was more capable than `for_each`, but that no longer exists.
The `itertools` crate has `Itertools::foreach` with the same behavior,
but thankfully the names won't collide. The `rayon` crate also has a
`ParallelIterator::for_each` where simple `for` loops aren't possible.
> I really wish we had `for_each` on seq iterators. Having to use a
> dummy operation is annoying. - [@nikomatsakis][1]
[1]: https://github.com/nikomatsakis/rayon/pull/367#issuecomment-308455185
[libcore/cmp] Expand Ord/PartialOrd Derivable doc for enum types
Expand Derivable docblock section for `Ord` and `PartialOrd` to cover
`enum` types, in addition to the existing language explaining it for
`struct` types.
Update docs for fmt::write.
#29355
I reworded it slightly to make it more clear that the function only take
two arguments - the output and the Arguments struct that can be
generated from the format_args! macro.
r? @steveklabnik
Reuse the mem::swap optimizations to speed up slice::rotate
This is most helpful for compound types where LLVM didn't vectorize the loop. Highlight: bench slice::rotate_medium_by727_strings gets 38% faster.
Exposes the swapping logic from PR https://github.com/rust-lang/rust/pull/40454 as `pub unsafe fn ptr::swap_nonoverlapping` under library feature `swap_nonoverlapping` https://github.com/rust-lang/rust/issues/42818.
(The new method seemed plausible, and was the simplest way to share the logic. I'm not attached to it, though, so let me know if a different way would be better.)
Fix NaN handling in is_sign_negative/positive
This would be my proposed fix for the #42425 provided we decide it is indeed a problem.
Note this would technically be a breaking change to a stable API. We might want to consider deprecating these methods and adding new ones.
Expand Derivable docblock section for `Ord` and `PartialOrd` to cover
`enum` types, in addition to the existing language explaining it for
`struct` types.
assert_eq failure message easier to read
By having the left and right strings aligned with one another it helps spot the difference between the two far quicker than if they are on the same line.
E.g.
Before:
```
thread 'tests::test_safe_filename' panicked at 'assertion failed: `(left == right)` left: `"-aandb--S123.html"` right: `"-aandb-S123.html"`',
```
After:
```
thread 'tests::test_safe_filename' panicked at 'assertion failed: `(left == right)`
left: `"-aandb--S123.html"`
right: `"-aandb-S123.html"`',
```
When the strings are both on the same line it take a lot longer to spot the difference. It is a small change but the small time savings add up with repetition. This would help Rust be an excellent language to write tests in out of the box.
Closes https://github.com/rust-lang/rust/issues/41615
