Add key and value methods to DebugMap
Implementation PR for an active (not approved) RFC: https://github.com/rust-lang/rfcs/pull/2696.
Add two new methods to `std::fmt::DebugMap` for writing the key and value part of a map entry separately:
```rust
impl<'a, 'b: 'a> DebugMap<'a, 'b> {
pub fn key(&mut self, key: &dyn Debug) -> &mut Self;
pub fn value(&mut self, value: &dyn Debug) -> &mut Self;
}
```
I want to do this so that I can write a `serde::Serializer` that forwards to our format builders, so that any `T: Serialize` can also be treated like a `T: Debug`.
Only call the closure parameter of Iterator::is_sorted_by_key once per item
See https://github.com/rust-lang/rust/issues/53485#issuecomment-472314004.
This changes `Iterator::is_sorted_by_key` to only call the given closure once for each item, which allows us to pass the items to the closure by value instead of by reference.
**Important**: `is_sorted_by_key` for slices and slice iterators is now no longer implemented in terms of the custom `slice::Iter::is_sorted_by` implementation. It's a trade-off: we could forward `slice::Iter::is_sorted_by_key` to it directly for potential SIMD benefits, but that would mean that the closure is potentially called twice for (almost) every element of the slice.
- uses a never-stable core::array::LengthAtMost32 to bound the impls
- includes a custom error message to avoid mentioning LengthAtMost32 too often
- doesn't use macros for the slice implementations to avoid #62433
First question mark in doctest
We have had `?` for `Result`s in doctests for some time, but so far haven't used them in doctests. With this PR, I want to start the de-`unwrap`ping of doctests – and the discussion on where to do so.
There is one downside, which is that the code can no longer be copied into a plain `main()` method, on the other hand, there should be a workable error if one does this.
Improve documentation for built-in macros
This is the `libcore` part of https://github.com/rust-lang/rust/pull/62086.
Right now the only effect is improved documentation.
The changes in the last few commits are required to make the `libcore` change compile successfully.
Refactor unicode.py script
Hi, I noticed that the `unicode.py` script used some deprecated escapes in regular expressions. E.g. `\d`, `\w`, `\.` will be illegal in the future without "raw strings". This is now fixed. I have also cleaned up the script quite a bit.
## Escape deprecation
OK (note the `r`):
`re.compile(r"\d")`
Deprecated (from Python 3.6 onwards, see [here][link1] and [here][link2]):
`re.compile("\d")`.
[link1]: https://docs.python.org/3.6/whatsnew/3.6.html#deprecated-python-behavior
[link2]: https://bugs.python.org/issue27364
This was evident running the script using Python 3.7 like so:
```
$ python3 -Wall unicode.py
unicode.py:227: DeprecationWarning: invalid escape sequence \w
re1 = re.compile("^ *([0-9A-F]+) *; *(\w+)")
unicode.py:228: DeprecationWarning: invalid escape sequence \.
re2 = re.compile("^ *([0-9A-F]+)\.\.([0-9A-F]+) *; *(\w+)")
unicode.py:453: DeprecationWarning: invalid escape sequence \d
pattern = "for Version (\d+)\.(\d+)\.(\d+) of the Unicode"
```
The documentation states that
> A backslash-character pair that is not a valid escape sequence now generates a DeprecationWarning. Although this will eventually become a SyntaxError, that will not be for several Python releases.
## Testing
To test my changes, I had to add support for choosing the Unicode version to use. The script will default to latest release (which is 12.0.0 at the moment, repo has 11.0.0 checked in).
The script generates the exact same output for version 11.0.0 with Python 2.7 and 3.7 and no longer generates any deprecation warnings:
```
$ python3 -Wall unicode.py -v 11.0.0
Using Unicode version: 11.0.0
Regenerated tables.rs.
$ git diff tables.rs
$ python2 -Wall unicode.py -v 11.0.0
Using Unicode version: 11.0.0
Regenerated tables.rs.
$ git diff tables.rs
$ python2 --version
Python 2.7.16
$ python3 --version
Python 3.7.3
```
## Extra functionality
Furthermore, the script will check and download the latest Unicode version by default (without the `-v` argument). The `--help` is below:
```
$ ./unicode.py --help
usage: unicode.py [-h] [-v VERSION]
Regenerate Unicode tables (tables.rs).
optional arguments:
-h, --help show this help message and exit
-v VERSION, --version VERSION
Unicode version to use (if not specified, defaults to
latest available final release).
```
## Cleanups
I have cleaned up the code quite a bit, with Python best practices and code style in mind. I'm happy to provide more details and rationale for all my changes if the reviewers so desire.
One externally visible change is that the Unicode data will now be downloaded into `src/libcore/unicode/downloaded` directory suffixed by Unicode version:
```
$ pwd
.../rust/src/libcore/unicode
$ exa -T downloaded/
downloaded
├── 11.0.0
│ ├── DerivedCoreProperties.txt
│ ├── DerivedNormalizationProps.txt
│ ├── PropList.txt
│ ├── ReadMe.txt
│ ├── Scripts.txt
│ ├── SpecialCasing.txt
│ └── UnicodeData.txt
└── 12.0.0
├── DerivedCoreProperties.txt
├── DerivedNormalizationProps.txt
├── PropList.txt
├── ReadMe.txt
├── Scripts.txt
├── SpecialCasing.txt
└── UnicodeData.txt
```
When possible without changing semantics, implement Iterator::last in terms of DoubleEndedIterator::next_back for types in liballoc and libcore.
Provided that the iterator has finite length and does not trigger user-provided code, this is safe.
What follows is a full list of the DoubleEndedIterators in liballoc/libcore and whether this optimization is safe, and if not, why not.
src/liballoc/boxed.rs
Box: Pass through to avoid defeating optimization of the underlying DoubleIterator implementation. This has no correctness impact.
src/liballoc/collections/binary_heap.rs
Iter: Pass through to avoid defeating optimizations on slice::Iter
IntoIter: Not safe, changes Drop order
Drain: Not safe, changes Drop order
src/liballoc/collections/btree/map.rs
Iter: Safe to call next_back, invokes no user defined code.
IterMut: ditto
IntoIter: Not safe, changes Drop order
Keys: Safe to call next_back, invokes no user defined code.
Values: ditto
ValuesMut: ditto
Range: ditto
RangeMut: ditto
src/liballoc/collections/btree/set.rs
Iter: Safe to call next_back, invokes no user defined code.
IntoIter: Not safe, changes Drop order
Range: Safe to call next_back, invokes no user defined code.
src/liballoc/collections/linked_list.rs
Iter: Safe to call next_back, invokes no user defined code.
IterMut: ditto
IntoIter: Not safe, changes Drop order
src/liballoc/collections/vec_deque.rs
Iter: Safe to call next_back, invokes no user defined code.
IterMut: ditto
IntoIter: Not safe, changes Drop order
Drain: ditto
src/liballoc/string.rs
Drain: Safe because return type is a primitive (char)
src/liballoc/vec.rs
IntoIter: Not safe, changes Drop order
Drain: ditto
Splice: ditto
src/libcore/ascii.rs
EscapeDefault: Safe because return type is a primitive (u8)
src/libcore/iter/adapters/chain.rs
Chain: Not safe, invokes user defined code (Iterator impl)
src/libcore/iter/adapters/flatten.rs
FlatMap: Not safe, invokes user defined code (Iterator impl)
Flatten: ditto
FlattenCompat: ditto
src/libcore/iter/adapters/mod.rs
Rev: Not safe, invokes user defined code (Iterator impl)
Copied: ditto
Cloned: Not safe, invokes user defined code (Iterator impl and T::clone)
Map: Not safe, invokes user defined code (Iterator impl + closure)
Filter: ditto
FilterMap: ditto
Enumerate: Not safe, invokes user defined code (Iterator impl)
Skip: ditto
Fuse: ditto
Inspect: ditto
src/libcore/iter/adapters/zip.rs
Zip: Not safe, invokes user defined code (Iterator impl)
src/libcore/iter/range.rs
ops::Range: Not safe, changes Drop order, but ALREADY HAS SPECIALIZATION
ops::RangeInclusive: ditto
src/libcore/iter/sources.rs
Repeat: Not safe, calling last should iloop.
Empty: No point, iterator is at most one item long.
Once: ditto
OnceWith: ditto
src/libcore/option.rs
Item: No point, iterator is at most one item long.
Iter: ditto
IterMut: ditto
IntoIter: ditto
src/libcore/result.rs
Iter: No point, iterator is at most one item long
IterMut: ditto
IntoIter: ditto
src/libcore/slice/mod.rs
Split: Not safe, invokes user defined closure
SplitMut: ditto
RSplit: ditto
RSplitMut: ditto
Windows: Safe, already has specialization
Chunks: ditto
ChunksMut: ditto
ChunksExact: ditto
ChunksExactMut: ditto
RChunks: ditto
RChunksMut: ditto
RChunksExact: ditto
RChunksExactMut: ditto
src/libcore/str/mod.rs
Chars: Safe, already has specialization
CharIndices: ditto
Bytes: ditto
Lines: Safe to call next_back, invokes no user defined code.
LinesAny: Deprecated
Everything that is generic over P: Pattern: Not safe because Pattern invokes user defined code.
SplitWhitespace: Safe to call next_back, invokes no user defined code.
SplitAsciiWhitespace: ditto
This is attempt 2 of #60130.
r? @sfackler
nth_back for chunks_exact
wip nth_back for chunks_exact
working nth_back for chunks exact
Signed-off-by: wizAmit <amitforfriends_dns@yahoo.com>
r? @timvermeulen
r? @scottmcm
Provided that the iterator has finite length and does not trigger user-provided code, this is safe.
What follows is a full list of the DoubleEndedIterators in liballoc/libcore and whether this optimization is safe, and if not, why not.
src/liballoc/boxed.rs
Box: Pass through to avoid defeating optimization of the underlying DoubleIterator implementation. This has no correctness impact.
src/liballoc/collections/binary_heap.rs
Iter: Pass through to avoid defeating optimizations on slice::Iter
IntoIter: Not safe, changes Drop order
Drain: Not safe, changes Drop order
src/liballoc/collections/btree/map.rs
Iter: Safe to call next_back, invokes no user defined code.
IterMut: ditto
IntoIter: Not safe, changes Drop order
Keys: Safe to call next_back, invokes no user defined code.
Values: ditto
ValuesMut: ditto
Range: ditto
RangeMut: ditto
src/liballoc/collections/btree/set.rs
Iter: Safe to call next_back, invokes no user defined code.
IntoIter: Not safe, changes Drop order
Range: Safe to call next_back, invokes no user defined code.
src/liballoc/collections/linked_list.rs
Iter: Safe to call next_back, invokes no user defined code.
IterMut: ditto
IntoIter: Not safe, changes Drop order
src/liballoc/collections/vec_deque.rs
Iter: Safe to call next_back, invokes no user defined code.
IterMut: ditto
IntoIter: Not safe, changes Drop order
Drain: ditto
src/liballoc/string.rs
Drain: Safe because return type is a primitive (char)
src/liballoc/vec.rs
IntoIter: Not safe, changes Drop order
Drain: ditto
Splice: ditto
src/libcore/ascii.rs
EscapeDefault: Safe because return type is a primitive (u8)
src/libcore/iter/adapters/chain.rs
Chain: Not safe, invokes user defined code (Iterator impl)
src/libcore/iter/adapters/flatten.rs
FlatMap: Not safe, invokes user defined code (Iterator impl)
Flatten: ditto
FlattenCompat: ditto
src/libcore/iter/adapters/mod.rs
Rev: Not safe, invokes user defined code (Iterator impl)
Copied: ditto
Cloned: Not safe, invokes user defined code (Iterator impl and T::clone)
Map: Not safe, invokes user defined code (Iterator impl + closure)
Filter: ditto
FilterMap: ditto
Enumerate: Not safe, invokes user defined code (Iterator impl)
Skip: ditto
Fuse: ditto
Inspect: ditto
src/libcore/iter/adapters/zip.rs
Zip: Not safe, invokes user defined code (Iterator impl)
src/libcore/iter/range.rs
ops::Range: Not safe, changes Drop order, but ALREADY HAS SPECIALIZATION
ops::RangeInclusive: ditto
src/libcore/iter/sources.rs
Repeat: Not safe, calling last should iloop.
Empty: No point, iterator is at most one item long.
Once: ditto
OnceWith: ditto
src/libcore/option.rs
Item: No point, iterator is at most one item long.
Iter: ditto
IterMut: ditto
IntoIter: ditto
src/libcore/result.rs
Iter: No point, iterator is at most one item long
IterMut: ditto
IntoIter: ditto
src/libcore/slice/mod.rs
Split: Not safe, invokes user defined closure
SplitMut: ditto
RSplit: ditto
RSplitMut: ditto
Windows: Safe, already has specialization
Chunks: ditto
ChunksMut: ditto
ChunksExact: ditto
ChunksExactMut: ditto
RChunks: ditto
RChunksMut: ditto
RChunksExact: ditto
RChunksExactMut: ditto
src/libcore/str/mod.rs
Chars: Safe, already has specialization
CharIndices: ditto
Bytes: ditto
Lines: Safe to call next_back, invokes no user defined code.
LinesAny: Deprecated
Everything that is generic over P: Pattern: Not safe because Pattern invokes user defined code.
SplitWhitespace: Safe to call next_back, invokes no user defined code.
SplitAsciiWhitespace: ditto
