This implements RFC 39. Omitted lifetimes in return values will now be
inferred to more useful defaults, and an error is reported if a lifetime
in a return type is omitted and one of the two lifetime elision rules
does not specify what it should be.
This primarily breaks two uncommon code patterns. The first is this:
unsafe fn get_foo_out_of_thin_air() -> &Foo {
...
}
This should be changed to:
unsafe fn get_foo_out_of_thin_air() -> &'static Foo {
...
}
The second pattern that needs to be changed is this:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed {
Owned(format!("hello world"))
}
Change code like this to:
enum MaybeBorrowed<'a> {
Borrowed(&'a str),
Owned(String),
}
fn foo() -> MaybeBorrowed<'static> {
Owned(format!("hello world"))
}
Closes#15552.
[breaking-change]
Reimplement the string slice's `Iterator<char>` by wrapping the already efficient
slice iterator.
The iterator uses our guarantee that the string contains valid UTF-8, but its only unsafe
code is transmuting the decoded `u32` into `char`.
Benchmarks suggest that the runtime of `Chars` benchmarks are reduced by up to 30%,
runtime of `Chars` reversed reduced by up to 60%.
```
BEFORE
test str::bench::char_indicesator ... bench: 124 ns/iter (+/- 1)
test str::bench::char_indicesator_rev ... bench: 188 ns/iter (+/- 9)
test str::bench::char_iterator ... bench: 122 ns/iter (+/- 2)
test str::bench::char_iterator_ascii ... bench: 302 ns/iter (+/- 41)
test str::bench::char_iterator_for ... bench: 123 ns/iter (+/- 4)
test str::bench::char_iterator_rev ... bench: 189 ns/iter (+/- 14)
test str::bench::char_iterator_rev_for ... bench: 177 ns/iter (+/- 4)
AFTER
test str::bench::char_indicesator ... bench: 85 ns/iter (+/- 3)
test str::bench::char_indicesator_rev ... bench: 82 ns/iter (+/- 2)
test str::bench::char_iterator ... bench: 100 ns/iter (+/- 3)
test str::bench::char_iterator_ascii ... bench: 317 ns/iter (+/- 3)
test str::bench::char_iterator_for ... bench: 86 ns/iter (+/- 2)
test str::bench::char_iterator_rev ... bench: 80 ns/iter (+/- 6)
test str::bench::char_iterator_rev_for ... bench: 68 ns/iter (+/- 0)
```
Note: Branch name is no longer indicative of the implementation.
except where trait objects are involved.
Part of issue #15349, though I'm leaving it open for trait objects.
Cross borrowing for trait objects remains because it is needed until we
have DST.
This will break code like:
fn foo(x: &int) { ... }
let a = box 3i;
foo(a);
Change this code to:
fn foo(x: &int) { ... }
let a = box 3i;
foo(&*a);
[breaking-change]
Someone asked for an example usage of this on IRC, so I tossed together the simplest one. Obviously, this isn't up to snuff, but it's better than nothing.
- `width()` computes the displayed width of a string, ignoring the width of control characters.
- arguably we might do *something* else for control characters, but the question is, what?
- users who want to do something else can iterate over chars()
- `graphemes()` returns a `Graphemes` struct, which implements an iterator over the grapheme clusters of a &str.
- fully compliant with [UAX#29](http://www.unicode.org/reports/tr29/#Grapheme_Cluster_Boundaries)
- passes all [Unicode-supplied tests](http://www.unicode.org/reports/tr41/tr41-15.html#Tests29)
- added code to generate additionial categories in `unicode.py`
- `Cn` aka `Not_Assigned`
- categories necessary for grapheme cluster breaking
- tidied up the exports from libunicode
- all exports are exposed through a module rather than directly at crate root.
- std::prelude imports UnicodeChar and UnicodeStrSlice from std::char and std::str rather than directly from libunicode
closes#7043
- Graphemes and GraphemeIndices structs implement iterators over
grapheme clusters analogous to the Chars and CharOffsets for chars in
a string. Iterator and DoubleEndedIterator are available for both.
- tidied up the exports for libunicode. crate root exports are now moved
into more appropriate module locations:
- UnicodeStrSlice, Words, Graphemes, GraphemeIndices are in str module
- UnicodeChar exported from char instead of crate root
- canonical_combining_class is exported from str rather than crate root
Since libunicode's exports have changed, programs that previously relied
on the old export locations will need to change their `use` statements
to reflect the new ones. See above for more information on where the new
exports live.
closes#7043
[breaking-change]
This PR is the outcome of the library stabilization meeting for the
`liballoc::owned` and `libcore::cell` modules.
Aside from the stability attributes, there are a few breaking changes:
* The `owned` modules is now named `boxed`, to better represent its
contents. (`box` was unavailable, since it's a keyword.) This will
help avoid the misconception that `Box` plays a special role wrt
ownership.
* The `AnyOwnExt` extension trait is renamed to `BoxAny`, and its `move`
method is renamed to `downcast`, in both cases to improve clarity.
* The recently-added `AnySendOwnExt` extension trait is removed; it was
not being used and is unnecessary.
[breaking-change]
This PR is the outcome of the library stabilization meeting for the
`liballoc::owned` and `libcore::cell` modules.
Aside from the stability attributes, there are a few breaking changes:
* The `owned` modules is now named `boxed`, to better represent its
contents. (`box` was unavailable, since it's a keyword.) This will
help avoid the misconception that `Box` plays a special role wrt
ownership.
* The `AnyOwnExt` extension trait is renamed to `BoxAny`, and its `move`
method is renamed to `downcast`, in both cases to improve clarity.
* The recently-added `AnySendOwnExt` extension trait is removed; it was
not being used and is unnecessary.
[breaking-change]
Add libunicode; move unicode functions from core
- created new crate, libunicode, below libstd
- split `Char` trait into `Char` (libcore) and `UnicodeChar` (libunicode)
- Unicode-aware functions now live in libunicode
- `is_alphabetic`, `is_XID_start`, `is_XID_continue`, `is_lowercase`,
`is_uppercase`, `is_whitespace`, `is_alphanumeric`, `is_control`, `is_digit`,
`to_uppercase`, `to_lowercase`
- added `width` method in UnicodeChar trait
- determines printed width of character in columns, or None if it is a non-NULL control character
- takes a boolean argument indicating whether the present context is CJK or not (characters with 'A'mbiguous widths are double-wide in CJK contexts, single-wide otherwise)
- split `StrSlice` into `StrSlice` (libcore) and `UnicodeStrSlice` (libunicode)
- functionality formerly in `StrSlice` that relied upon Unicode functionality from `Char` is now in `UnicodeStrSlice`
- `words`, `is_whitespace`, `is_alphanumeric`, `trim`, `trim_left`, `trim_right`
- also moved `Words` type alias into libunicode because `words` method is in `UnicodeStrSlice`
- unified Unicode tables from libcollections, libcore, and libregex into libunicode
- updated `unicode.py` in `src/etc` to generate aforementioned tables
- generated new tables based on latest Unicode data
- added `UnicodeChar` and `UnicodeStrSlice` traits to prelude
- libunicode is now the collection point for the `std::char` module, combining the libunicode functionality with the `Char` functionality from libcore
- thus, moved doc comment for `char` from `core::char` to `unicode::char`
- libcollections remains the collection point for `std::str`
The Unicode-aware functions that previously lived in the `Char` and `StrSlice` traits are no longer available to programs that only use libcore. To regain use of these methods, include the libunicode crate and `use` the `UnicodeChar` and/or `UnicodeStrSlice` traits:
extern crate unicode;
use unicode::UnicodeChar;
use unicode::UnicodeStrSlice;
use unicode::Words; // if you want to use the words() method
NOTE: this does *not* impact programs that use libstd, since UnicodeChar and UnicodeStrSlice have been added to the prelude.
closes#15224
[breaking-change]
