rust/src/liballoc/string.rs, branch 1.36.0

Revert "Add implementations of last in terms of next_back on a bunch of DoubleEndedIterators."

2019-05-28T19:55:26+00:00

This reverts commit 3e86cf36b5114f201868bf459934fe346a76a2d4.

Rollup merge of #59825 - jsgf:from-ref-string, r=sfackler

2019-05-16T08:43:24+00:00

string: implement From<&String> for String Allow Strings to be created from borrowed Strings. This is mostly to make things like passing `&String` to an `impl Into` parameter frictionless. Fixes #59827.

Rollup merge of #60130 - khuey:efficient_last, r=sfackler

2019-05-14T20:00:09+00:00

Add implementations of last in terms of next_back on a bunch of DoubleEndedIterators Provided a `DoubleEndedIterator` has finite length, `Iterator::last` is equivalent to `DoubleEndedIterator::next_back`. But searching forwards through the iterator when it's unnecessary is obviously not good for performance. I ran into this on one of the collection iterators. I tried adding appropriate overloads for a bunch of the iterator adapters like filter, map, etc, but I ran into a lot of type inference failures after doing so. The other interesting case is what to do with `Repeat`. Do we consider it part of the contract that `Iterator::last` will loop forever on it? The docs do say that the iterator will be evaluated until it returns None. This is also relevant for the adapters, it's trivially easy to observe whether a `Map` adapter invoked its closure a zillion times or just once for the last element.

Add examples of ordered retain

2019-05-11T01:01:50+00:00

Document the order of {Vec,VecDeque,String}::retain

2019-04-30T01:32:05+00:00

It's natural for `retain` to work in order from beginning to end, but this wasn't actually documented to be the case. If we actually promise this, then the caller can do useful things like track the index of each element being tested, as [discussed in the forum][1]. This is now documented for `Vec`, `VecDeque`, and `String`. [1]: https://users.rust-lang.org/t/vec-retain-by-index/27697 `HashMap` and `HashSet` also have `retain`, and the `hashbrown` implementation does happen to use a plain `iter()` order too, but it's not certain that this should always be the case for these types.

Add implementations of last in terms of next_back on a bunch of DoubleEndedIterators.

2019-04-20T04:52:43+00:00

r?Manishearth

string: implement From<&String> for String

2019-04-09T23:52:05+00:00

Allow Strings to be created from borrowed Strings. This is mostly to make things like passing &String to an `impl Into` parameter frictionless.

Use lifetime contravariance to elide more lifetimes in core+alloc+std

2019-03-10T03:10:28+00:00

Add a convert::Infallible empty enum, make string::ParseError an alias

2019-02-13T17:00:18+00:00

libs: doc comments

2019-02-10T23:57:25+00:00