This PR implements [RFC 1192](https://github.com/rust-lang/rfcs/blob/master/text/1192-inclusive-ranges.md), which is triple-dot syntax for inclusive range expressions. The new stuff is behind two feature gates (one for the syntax and one for the std::ops types). This replaces the deprecated functionality in std::iter. Along the way I simplified the desugaring for all ranges.
This is my first contribution to rust which changes more than one character outside of a test or comment, so please review carefully! Some of the individual commit messages have more of my notes. Also thanks for putting up with my dumb questions in #rust-internals.
- For implementing `std::ops::RangeInclusive`, I took @Stebalien's suggestion from https://github.com/rust-lang/rfcs/pull/1192#issuecomment-137864421. It seemed to me to make the implementation easier and increase type safety. If that stands, the RFC should be amended to avoid confusion.
- I also kind of like @glaebhoerl's [idea](https://github.com/rust-lang/rfcs/pull/1254#issuecomment-147815299), which is unified inclusive/exclusive range syntax something like `x>..=y`. We can experiment with this while everything is behind a feature gate.
- There are a couple of FIXMEs left (see the last commit). I didn't know what to do about `RangeArgument` and I haven't added `Index` impls yet. Those should be discussed/finished before merging.
cc @Gankro since you [complained](https://www.reddit.com/r/rust/comments/3xkfro/what_happened_to_inclusive_ranges/cy5j0yq)
cc #27777#30877rust-lang/rust#1192rust-lang/rfcs#1254
relevant to #28237 (tracking issue)
Use `drop_in_place` in Vec and VecDeque
We can use drop_in_place's DST capabilities directly in Vec::drop and similarly in VecDeque::drop. I verfied this has the same effect as the previous `needs_drop` code; `drop_in_place` it itself an intrinsic.
The VecDeque replacement should be more efficient too, even in release mode (slice iteration makes a more efficient loop than the deque iterator).
Just like for Vec. This should benefit both non-optimized and optimized
performance. Non-optimized since the intrinsic drop_in_place is easily
removed, and optimized because iterating the slices is more efficient
than using the VecDeque iterators.
This commit is the result of the FCPs ending for the 1.8 release cycle for both
the libs and the lang suteams. The full list of changes are:
Stabilized
* `braced_empty_structs`
* `augmented_assignments`
* `str::encode_utf16` - renamed from `utf16_units`
* `str::EncodeUtf16` - renamed from `Utf16Units`
* `Ref::map`
* `RefMut::map`
* `ptr::drop_in_place`
* `time::Instant`
* `time::SystemTime`
* `{Instant,SystemTime}::now`
* `{Instant,SystemTime}::duration_since` - renamed from `duration_from_earlier`
* `{Instant,SystemTime}::elapsed`
* Various `Add`/`Sub` impls for `Time` and `SystemTime`
* `SystemTimeError`
* `SystemTimeError::duration`
* Various impls for `SystemTimeError`
* `UNIX_EPOCH`
* `ops::{Add,Sub,Mul,Div,Rem,BitAnd,BitOr,BitXor,Shl,Shr}Assign`
Deprecated
* Scoped TLS (the `scoped_thread_local!` macro)
* `Ref::filter_map`
* `RefMut::filter_map`
* `RwLockReadGuard::map`
* `RwLockWriteGuard::map`
* `Condvar::wait_timeout_with`
Closes#27714Closes#27715Closes#27746Closes#27748Closes#27908Closes#29866
In particular, uses of inclusive ranges within the standard library are
still waiting. Slices and collections can be sliced with `usize` and
`Range*<usize>`, but not yet `Range*Inclusive<usize>`.
Also, we need to figure out what to do about `RangeArgument`. Currently
it has `start()` and `end()` methods which are pretty much identical to
`Range::start` and `Range::end`. For the same reason as Range itself,
these methods can't express a range such as `0...255u8` without
overflow. The easiest choice, it seems to me, is either changing the
meaning of `end()` to be inclusive, or adding a new method, say
`last()`, that is inclusive and specifying that `end()` returns `None`
in cases where it would overflow. Changing the semantics would be a
breaking change, but `RangeArgument` is unstable so maybe we should do
it anyway.
The first time I read the docs for `insert()`, I thought it was saying it didn't update existing *values*, and I was confused. Reword the docs to make it clear that `insert()` does update values.
The first time I read the docs for `insert()`, I thought it was saying
it didn't update existing *values*, and I was confused. Reword the docs
to make it clear that `insert()` does update values.
collections: Use slice parts in PartialEq for VecDeque
This improves == for VecDeque by using the slice representation.
This will also improve further if codegen for slice comparison improves.
Benchmark run of 1000 u64 elements, comparing for equality (all equal).
Cpu time to compare the vecdeques is reduced to less than 50% of what it
was before.
```
test test_eq_u64 ... bench: 1,885 ns/iter (+/- 163) = 4244 MB/s
test test_eq_new_u64 ... bench: 802 ns/iter (+/- 100) = 9975 MB/s
```
When I last did a pass through the string documentation, I focused on
consistency across similar functions. Unfortunately, I missed some
details. This example was _too_ consistent: it wasn't actually accurate!
This commit fixes the docs do both be more accurate and to explain why
the return type is a Cow<'a, str>.
First reported here:
https://www.reddit.com/r/rust/comments/44q9ms/stringfrom_utf8_lossy_doesnt_return_a_string/
Hash VecDeque in its slice parts
Use .as_slices() for a more efficient code path in VecDeque's Hash impl.
This still hashes the elements in the same order.
Before/after timing of VecDeque hashing 1024 elements of u8 and
u64 shows that the vecdeque now can match the Vec
(test_hashing_vec_of_u64 is the Vec run).
```
before
test test_hashing_u64 ... bench: 14,031 ns/iter (+/- 236) = 583 MB/s
test test_hashing_u8 ... bench: 7,887 ns/iter (+/- 65) = 129 MB/s
test test_hashing_vec_of_u64 ... bench: 6,578 ns/iter (+/- 76) = 1245 MB/s
after
running 5 tests
test test_hashing_u64 ... bench: 6,495 ns/iter (+/- 52) = 1261 MB/s
test test_hashing_u8 ... bench: 851 ns/iter (+/- 16) = 1203 MB/s
test test_hashing_vec_of_u64 ... bench: 6,499 ns/iter (+/- 59) = 1260 MB/s
```
This improves == for VecDeque by using the slice representation.
This will also improve further if codegen for slice comparison improves.
Benchmark run of 1000 u64 elements, comparing for equality (all equal).
Cpu time to compare the vecdeques is reduced to less than 50% of what it
was before.
```
test test_eq_u64 ... bench: 1,885 ns/iter (+/- 163) = 4244 MB/s
test test_eq_new_u64 ... bench: 802 ns/iter (+/- 100) = 9975 MB/s
```
Use .as_slices() for a more efficient code path in VecDeque's Hash impl.
This still hashes the elements in the same order.
Before/after timing of VecDeque hashing 1024 elements of u8 and
u64 shows that the vecdeque now can match the Vec
(test_hashing_vec_of_u64 is the Vec run).
before
test test_hashing_u64 ... bench: 14,031 ns/iter (+/- 236) = 583 MB/s
test test_hashing_u8 ... bench: 7,887 ns/iter (+/- 65) = 129 MB/s
test test_hashing_vec_of_u64 ... bench: 6,578 ns/iter (+/- 76) = 1245 MB/s
after
running 5 tests
test test_hashing_u64 ... bench: 6,495 ns/iter (+/- 52) = 1261 MB/s
test test_hashing_u8 ... bench: 851 ns/iter (+/- 16) = 1203 MB/s
test test_hashing_vec_of_u64 ... bench: 6,499 ns/iter (+/- 59) = 1260 MB/s
