The new `::ops::Range` has separated implementations for each of the
numeric types, while the old `::iter::Range` has one for type `Int`.
However, we do not take output bindings into account when selecting
traits. So it confuses `typeck` and makes the new range does not work as
good as the old one when it comes to type inference.
This patch implements `Iterator` for the new range for one type `Int`.
This limitation could be lifted, however, if we ever reconsider the
output types' role in type inference.
Closes#21595Closes#21649Closes#21672
This commit marks as `#[stable]`:
* The `Index` and `IndexMut` traits. These are stabilized as taking the
index itself *by reference*; after extensive discussion it was
determined that this is a better match with our choices
elsewhere (e.g. making comparison operators auto-reference), and that
the use cases for by-value indices are better handled through
`IndexSet`.
* The `Range`, `RangeFrom` and `RangeTo` structs, introduced for range
notation.
* Various impls of `Index` and `IndexMut`.
The `FullRange` struct is left unstable as we may wish to rename it to
`RangeFull` in the future.
This commit also *removes* the `Step` trait in favor of direct
implementation of iterator traits on ranges for integers. The `Step`
trait was not a terribly useful factoring internally, and it is likely
that external integer types are best off implementing range iterators
directly. It was removed to simplify the API surface. We can always
reintroduce `Step` later if it turns out to be useful.
Due to this removal, this is a:
[breaking-change]
This gets rid of the 'experimental' level, removes the non-staged_api
case (i.e. stability levels for out-of-tree crates), and lets the
staged_api attributes use 'unstable' and 'deprecated' lints.
This makes the transition period to the full feature staging design
a bit nicer.
This commit wraps up the adjustments to the iterator for recent language
changes.
* Moves `rposition` from `ExactSizeIterator` to `IteratorExt` using a
`where` clause, thereby removing the `ExactSizeIterator:
DoubleEndedIterator` constraint.
* Merges `MutableDoubleEndedIterator` into `IteratorExt`, renaming
`reverse_` to `reverse_in_place`.
* Merges `IteratorOrdExt`, `IteratorCloneExt` and `CloneIteratorExt`
into `IteratorExt` using `where` clauses.
Marks as `#[stable]`:
* the `iter` module itself
* `FromIterator`, `Extend`
* `Iterator`, `IteratorExt`
* `map`
* `filter`
* `filter_map`
* `skip_while`
* `take_while`
* `scan`
* `flat_map`
* `inspect`
* `collect`
* `fold`
* `all`
* `any`
* `find`
* `rposition`
* `max`, `min`
* Various adapter types related to the above methods
Because of the trait merging, this is a:
[breaking-change]
