This commit performs a second pass over the `std::string` module, performing the
following actions:
* The name `std::string` is now stable.
* The `String::from_utf8` function is now stable after having been altered to
return a new `FromUtf8Error` structure. The `FromUtf8Error` structure is now
stable as well as its `into_bytes` and `utf8_error` methods.
* The `String::from_utf8_lossy` function is now stable.
* The `String::from_chars` method is now deprecated in favor of `.collect()`
* The `String::from_raw_parts` method is now stable
* The `String::from_str` function remains experimental
* The `String::from_raw_buf` function remains experimental
* The `String::from_raw_buf_len` function remains experimental
* The `String::from_utf8_unchecked` function is now stable
* The `String::from_char` function is now deprecated in favor of
`repeat(c).take(n).collect()`
* The `String::grow` function is now deprecated in favor of
`.extend(repeat(c).take(n)`
* The `String::capacity` method is now stable
* The `String::reserve` method is now stable
* The `String::reserve_exact` method is now stable
* The `String::shrink_to_fit` method is now stable
* The `String::pop` method is now stable
* The `String::as_mut_vec` method is now stable
* The `String::is_empty` method is now stable
* The `IntoString` trait is now deprecated (there are no implementors)
* The `String::truncate` method is now stable
* The `String::insert` method is now stable
* The `String::remove` method is now stable
* The `String::push` method is now stable
* The `String::push_str` method is now stable
* The `String::from_utf16` function is now stable after its error type has now
become an opaque structure to carry more semantic information in the future.
A number of these changes are breaking changes, but the migrations should be
fairly straightforward on a case-by-case basis (outlined above where possible).
[breaking-change]
This commit starts out by consolidating all `str` extension traits into one
`StrExt` trait to be included in the prelude. This means that
`UnicodeStrPrelude`, `StrPrelude`, and `StrAllocating` have all been merged into
one `StrExt` exported by the standard library. Some functionality is currently
duplicated with the `StrExt` present in libcore.
This commit also currently avoids any methods which require any form of pattern
to operate. These functions will be stabilized via a separate RFC.
Next, stability of methods and structures are as follows:
Stable
* from_utf8_unchecked
* CowString - after moving to std::string
* StrExt::as_bytes
* StrExt::as_ptr
* StrExt::bytes/Bytes - also made a struct instead of a typedef
* StrExt::char_indices/CharIndices - CharOffsets was renamed
* StrExt::chars/Chars
* StrExt::is_empty
* StrExt::len
* StrExt::lines/Lines
* StrExt::lines_any/LinesAny
* StrExt::slice_unchecked
* StrExt::trim
* StrExt::trim_left
* StrExt::trim_right
* StrExt::words/Words - also made a struct instead of a typedef
Unstable
* from_utf8 - the error type was changed to a `Result`, but the error type has
yet to prove itself
* from_c_str - this function will be handled by the c_str RFC
* FromStr - this trait will have an associated error type eventually
* StrExt::escape_default - needs iterators at least, unsure if it should make
the cut
* StrExt::escape_unicode - needs iterators at least, unsure if it should make
the cut
* StrExt::slice_chars - this function has yet to prove itself
* StrExt::slice_shift_char - awaiting conventions about slicing and shifting
* StrExt::graphemes/Graphemes - this functionality may only be in libunicode
* StrExt::grapheme_indices/GraphemeIndices - this functionality may only be in
libunicode
* StrExt::width - this functionality may only be in libunicode
* StrExt::utf16_units - this functionality may only be in libunicode
* StrExt::nfd_chars - this functionality may only be in libunicode
* StrExt::nfkd_chars - this functionality may only be in libunicode
* StrExt::nfc_chars - this functionality may only be in libunicode
* StrExt::nfkc_chars - this functionality may only be in libunicode
* StrExt::is_char_boundary - naming is uncertain with container conventions
* StrExt::char_range_at - naming is uncertain with container conventions
* StrExt::char_range_at_reverse - naming is uncertain with container conventions
* StrExt::char_at - naming is uncertain with container conventions
* StrExt::char_at_reverse - naming is uncertain with container conventions
* StrVector::concat - this functionality may be replaced with iterators, but
it's not certain at this time
* StrVector::connect - as with concat, may be deprecated in favor of iterators
Deprecated
* StrAllocating and UnicodeStrPrelude have been merged into StrExit
* eq_slice - compiler implementation detail
* from_str - use the inherent parse() method
* is_utf8 - call from_utf8 instead
* replace - call the method instead
* truncate_utf16_at_nul - this is an implementation detail of windows and does
not need to be exposed.
* utf8_char_width - moved to libunicode
* utf16_items - moved to libunicode
* is_utf16 - moved to libunicode
* Utf16Items - moved to libunicode
* Utf16Item - moved to libunicode
* Utf16Encoder - moved to libunicode
* AnyLines - renamed to LinesAny and made a struct
* SendStr - use CowString<'static> instead
* str::raw - all functionality is deprecated
* StrExt::into_string - call to_string() instead
* StrExt::repeat - use iterators instead
* StrExt::char_len - use .chars().count() instead
* StrExt::is_alphanumeric - use .chars().all(..)
* StrExt::is_whitespace - use .chars().all(..)
Pending deprecation -- while slicing syntax is being worked out, these methods
are all #[unstable]
* Str - while currently used for generic programming, this trait will be
replaced with one of [], deref coercions, or a generic conversion trait.
* StrExt::slice - use slicing syntax instead
* StrExt::slice_to - use slicing syntax instead
* StrExt::slice_from - use slicing syntax instead
* StrExt::lev_distance - deprecated with no replacement
Awaiting stabilization due to patterns and/or matching
* StrExt::contains
* StrExt::contains_char
* StrExt::split
* StrExt::splitn
* StrExt::split_terminator
* StrExt::rsplitn
* StrExt::match_indices
* StrExt::split_str
* StrExt::starts_with
* StrExt::ends_with
* StrExt::trim_chars
* StrExt::trim_left_chars
* StrExt::trim_right_chars
* StrExt::find
* StrExt::rfind
* StrExt::find_str
* StrExt::subslice_offset
`String::push(&mut self, ch: char)` currently has a single code path that calls `Char::encode_utf8`. This adds a fast path for ASCII `char`s, which are represented as a single byte in UTF-8.
Benchmarks of stage1 libcollections at the intermediate commit show that the fast path very significantly improves the performance of repeatedly pushing an ASCII `char`, but does not significantly affect the performance for a non-ASCII `char` (where the fast path is not taken).
```
bench_push_char_one_byte 59552 ns/iter (+/- 2132) = 167 MB/s
bench_push_char_one_byte_with_fast_path 6563 ns/iter (+/- 658) = 1523 MB/s
bench_push_char_two_bytes 71520 ns/iter (+/- 3541) = 279 MB/s
bench_push_char_two_bytes_with_slow_path 71452 ns/iter (+/- 4202) = 279 MB/s
bench_push_str_one_byte 38910 ns/iter (+/- 2477) = 257 MB/s
```
A benchmark of pushing a one-byte-long `&str` is added for comparison, but its performance [has varied a lot lately](https://github.com/rust-lang/rust/pull/19640#issuecomment-67741561). (When the input is fixed, `s.push_str("x")` could be used just as well as `s.push('x')`.)
TL;DR I wrongly implemented these two ops, namely `"prefix" + "suffix".to_string()` gives back `"suffixprefix"`. Let's remove them.
The correct implementation of these operations (`lhs.clone().push_str(rhs.as_slice())`) is really wasteful, because the lhs has to be cloned and the rhs gets moved/consumed just to be dropped (no buffer reuse). For this reason, I'd prefer to drop the implementation instead of fixing it. This leaves us with the fact that you'll be able to do `String + &str` but not `&str + String`, which may be unexpected.
r? @aturon
Closes#19952
`String::push(&mut self, ch: char)` currently has a single code path
that calls `Char::encode_utf8`.
Perhaps it could be faster for ASCII `char`s, which are represented as
a single byte in UTF-8.
This commit leaves the method unchanged,
adds a copy of it with the fast path,
and adds benchmarks to compare them.
Results show that the fast path very significantly improves the performance
of repeatedly pushing an ASCII `char`,
but does not significantly affect the performance for a non-ASCII `char`
(where the fast path is not taken).
Output of `make check-stage1-collections NO_REBUILD=1 PLEASE_BENCH=1 TESTNAME=string::tests::bench_push`
```
test string::tests::bench_push_char_one_byte ... bench: 59552 ns/iter (+/- 2132) = 167 MB/s
test string::tests::bench_push_char_one_byte_with_fast_path ... bench: 6563 ns/iter (+/- 658) = 1523 MB/s
test string::tests::bench_push_char_two_bytes ... bench: 71520 ns/iter (+/- 3541) = 279 MB/s
test string::tests::bench_push_char_two_bytes_with_slow_path ... bench: 71452 ns/iter (+/- 4202) = 279 MB/s
test string::tests::bench_push_str ... bench: 24 ns/iter (+/- 2)
test string::tests::bench_push_str_one_byte ... bench: 38910 ns/iter (+/- 2477) = 257 MB/s
```
A benchmark of pushing a one-byte-long `&str` is added for comparison,
but its performance [has varied a lot lately](
https://github.com/rust-lang/rust/pull/19640#issuecomment-67741561).
(When the input is fixed, `s.push_str("x")` could be used
instead of `s.push('x')`.)
followed by a semicolon.
This allows code like `vec![1i, 2, 3].len();` to work.
This breaks code that uses macros as statements without putting
semicolons after them, such as:
fn main() {
...
assert!(a == b)
assert!(c == d)
println(...);
}
It also breaks code that uses macros as items without semicolons:
local_data_key!(foo)
fn main() {
println("hello world")
}
Add semicolons to fix this code. Those two examples can be fixed as
follows:
fn main() {
...
assert!(a == b);
assert!(c == d);
println(...);
}
local_data_key!(foo);
fn main() {
println("hello world")
}
RFC #378.
Closes#18635.
[breaking-change]
This commit performs a second pass stabilization of the `std::default` module.
The module was already marked `#[stable]`, and the inheritance of `#[stable]`
was removed since this attribute was applied. This commit adds the `#[stable]`
attribute to the trait definition and one method name, along with all
implementations found in the standard distribution.
This commit collapses the various prelude traits for slices into just one trait:
* SlicePrelude/SliceAllocPrelude => SliceExt
* CloneSlicePrelude/CloneSliceAllocPrelude => CloneSliceExt
* OrdSlicePrelude/OrdSliceAllocPrelude => OrdSliceExt
* PartialEqSlicePrelude => PartialEqSliceExt
This commit collapses the various prelude traits for slices into just one trait:
* SlicePrelude/SliceAllocPrelude => SliceExt
* CloneSlicePrelude/CloneSliceAllocPrelude => CloneSliceExt
* OrdSlicePrelude/OrdSliceAllocPrelude => OrdSliceExt
* PartialEqSlicePrelude => PartialEqSliceExt
Strings iterate to both char and &str, so it is natural it can also be extended or collected from an iterator of &str.
Apart from the trait implementations, `Extend<char>` is updated to use the iterator size hint, and the test added tests both the char and the &str versions of Extend and FromIterator.
Change Example to Examples.
Add a doctest that better demonstrates the utility of as_string.
Update the doctest example to use String instead of &String.
This commit is an implementation of [RFC 240][rfc] when applied to the standard
library. It primarily deprecates the entirety of `string::raw`, `vec::raw`,
`slice::raw`, and `str::raw` in favor of associated functions, methods, and
other free functions. The detailed renaming is:
* slice::raw::buf_as_slice => slice::with_raw_buf
* slice::raw::mut_buf_as_slice => slice::with_raw_mut_buf
* slice::shift_ptr => deprecated with no replacement
* slice::pop_ptr => deprecated with no replacement
* str::raw::from_utf8 => str::from_utf8_unchecked
* str::raw::c_str_to_static_slice => str::from_c_str
* str::raw::slice_bytes => deprecated for slice_unchecked (slight semantic diff)
* str::raw::slice_unchecked => str.slice_unchecked
* string::raw::from_parts => String::from_raw_parts
* string::raw::from_buf_len => String::from_raw_buf_len
* string::raw::from_buf => String::from_raw_buf
* string::raw::from_utf8 => String::from_utf8_unchecked
* vec::raw::from_buf => Vec::from_raw_buf
All previous functions exist in their `#[deprecated]` form, and the deprecation
messages indicate how to migrate to the newer variants.
[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0240-unsafe-api-location.md
[breaking-change]
Closes#17863
Throughout the docs, "failure" was replaced with "panics" if it means a
task panic. Otherwise, it remained as is, or changed to "errors" to
clearly differentiate it from a task panic.
