More methods for str boxes. (reduce Box<[u8]> ↔ Box<str> transmutes)
This is a follow-up to #41096 that adds safer methods for converting between `Box<str>` and `Box<[u8]>`. They're gated under a different feature from the `&mut str` methods because they may be too niche to include in public APIs, although having them internally helps reduce the number of transmutes the standard library uses.
What's added:
* `From<Box<str>> for Box<[u8]>`
* `<Box<str>>::into_boxed_bytes` (just calls `Into::into`)
* `alloc::str` (new module)
* `from_boxed_utf8` and `from_boxed_utf8_unchecked`, defined in `alloc:str`, exported in `collections::str`
* exports `from_utf8_mut` in `collections::str` (missed from previous PR)
specialize Extend for Vec with IntoIter
Before, `vec.extend(&other_vec)` was quite a bit faster than `vec.extend(other_vec)`. This allows extending by consuming a vec to use the same code as extending from a slice.
Add `as_bytes()` for `FromUtf8Error`.
This change allows to obtain an underlying invalid UTF-8 bytes without `FromUtf8Error` destruction. Such method may be useful for example in a library that attempts to save both valid and invalid UTF-8 strings in some struct and to be able to provide immutable access to it without destruction.
Personally without this change I ended with `Result<String, (Vec<u8>, Utf8Error)`, which almost copies the functionality of `FromUtf8Error`, but allows immutable view access.
Specialize Vec::from_elem to use calloc
Fixes#38723. This specializes the implementation for `u8` only, but it could be extended to other zeroable types if desired.
I haven't tested this extensively, but I did verify that it gives the expected performance boost for large `vec![0; n]` allocations with both alloc_system and jemalloc, on Linux. (I have not tested or even built the Windows code.)
* Bound:
* Added another example using RangeArgument to illustrate how Bound maps
to range endpoints.
* Added a note to the existing example that says that it's better to use
range syntax in most cases
* Added missing /// line
* binary_heap::PeakMut: s/Object representing/Structure wrapping
* added collections/hash_set/struct.HashSet.html to linkchecker whitelist
This change allows to obtain an underlying invalid UTF-8 bytes
without `FromUtf8Error` destruction. Such method may be useful
for example in a library that attempts to save both valid and
invalid UTF-8 strings in some struct and to be able to provide
immutable access to it without destruction.
* Changed btree_map's and hash_map's Entry (etc.) docs to be consistent
* Changed VecDeque's type and module summary sentences to be consistent
with each other as well as with other summary sentences in the module
* Changed HashMap's and HashSet's summary sentences to be less redundantly
phrased and also more consistant with the other summary sentences in the
module
* Also, added an example to Bound
* Added links where possible (limited because of facading)
* Changed references to methods from `foo()` to `foo` in module docs
* Changed references to methods from `HashMap::foo` to just `foo` in
top-level docs for `HashMap` and the `default` doc for `DefaultHasher`
* Various small other fixes
Add a resource-reusing method to `ToOwned`
`ToOwned::to_owned` generalizes `Clone::clone`, but `ToOwned` doesn't have an equivalent to `Clone::clone_from`. This PR adds such a method as `clone_into` under a new unstable feature `toowned_clone_into`.
Analogous to `clone_from`, this has the obvious default implementation in terms of `to_owned`. I've updated the `libcollections` impls: for `T:Clone` it uses `clone_from`, for `[T]` I moved the code from `Vec::clone_from` and implemented that in terms of this, and for `str` it's a predictable implementation in terms of `[u8]`.
Used it in `Cow::clone_from` to reuse resources when both are `Cow::Owned`, and added a test that `Cow<str>` thus keeps capacity in `clone_from` in that situation.
The obvious question: is this the right place for the method?
- It's here so it lives next to `to_owned`, making the default implementation reasonable, and avoiding another trait. But allowing method syntax forces a name like `clone_into`, rather than something more consistent like `owned_from`.
- Another trait would allow `owned_from` and could support multiple owning types per borrow type. But it'd be another single-method trait that generalizes `Clone`, and I don't know how to give it a default impl in terms of `ToOwned::to_owned`, since a blanket would mean overlapping impls problems.
I did it this way as it's simpler and many of the `Borrow`s/`AsRef`s don't make sense with `owned_from` anyway (`[T;1]:Borrow<[T]>`, `Arc<T>:Borrow<T>`, `String:AsRef<OsStr>`...). I'd be happy to re-do it the other way, though, if someone has a good solution for the default handling.
(I can also update with `CStr`, `OsStr`, and `Path` once a direction is decided.)
to_owned generalizes clone; this generalizes clone_from. Use to_owned to
give it a default impl. Customize the impl for [T], str, and T:Clone.
Use it in Cow::clone_from to reuse resources when cloning Owned into Owned.
Reduce str transmutes, add mut versions of methods.
When I was working on the various parts involved in #40380 one of the comments I got was the excess of transmutes necessary to make the changes work. This is part of a set of multiple changes I'd like to offer to fix this problem.
I think that having these methods is reasonable because they're already possible via transmutes, and it makes the code that uses them safer. I can also add `pub(crate)` to these methods for now if the libs team would rather not expose them to the public without an RFC.
Since my last PR led to linker failure, I'm now taking much smaller steps.
This only fixes some doc_markdown warnings; as they are in comments only,
we shouldn't get any problems building.
* Since the switch to pulldown-cmark reference links need a blank line
before the URLs.
* Reference link references are not case sensitive.
* Doc comments need to be indented uniformly otherwise rustdoc gets
confused.
Move libXtest into libX/tests
This change moves:
1. `libcoretest` into `libcore/tests`
2. `libcollectionstest` into `libcollections/tests`
This is a follow-up to #39561.
r? @alexcrichton
