Rollup merge of #42315 - scottmcm:rangefrom-sizehint, r=alexcrichton

RangeFrom should have an infinite size_hint

Before,
```rust
(0..).take(4).size_hint() == (0, Some(4))
```

With this change,
```rust
(0..).take(4).size_hint() == (4, Some(4))
```
This commit is contained in:
Mark Simulacrum 2017-05-31 10:52:48 -06:00 committed by GitHub
commit b62eb7fed8
3 changed files with 8 additions and 1 deletions

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@ -130,9 +130,10 @@ pub trait Iterator {
///
/// ```
/// // an infinite iterator has no upper bound
/// // and the maximum possible lower bound
/// let iter = 0..;
///
/// assert_eq!((0, None), iter.size_hint());
/// assert_eq!((usize::max_value(), None), iter.size_hint());
/// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]

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@ -543,6 +543,11 @@ impl<A: Step> Iterator for ops::RangeFrom<A> where
mem::swap(&mut n, &mut self.start);
Some(n)
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
(usize::MAX, None)
}
}
#[unstable(feature = "fused", issue = "35602")]

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@ -764,6 +764,7 @@ fn test_iterator_size_hint() {
let v2 = &[10, 11, 12];
let vi = v.iter();
assert_eq!((0..).size_hint(), (usize::MAX, None));
assert_eq!(c.size_hint(), (usize::MAX, None));
assert_eq!(vi.clone().size_hint(), (10, Some(10)));