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Make RangeInclusive::spec_try_(r)fold set exhausted consistently with next/next_back #164679

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Make RangeInclusive::spec_try_(r)fold set exhausted consistently with next/next_back #164679

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36 changes: 16 additions & 20 deletions library/core/src/iter/range.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1431,11 +1431,10 @@ impl<A: Step> RangeInclusiveIteratorImpl for ops::RangeInclusive<A> {
accum = f(accum, n)?;
}

self.exhausted = true;

if self.start == self.end {
accum = f(accum, self.start.clone())?;
}
let (n, o) = Step::forward_overflowing(self.start.clone(), 1);
let last = mem::replace(&mut self.start, n);
self.exhausted = o;
accum = f(accum, last)?;

try { accum }
}
Expand All @@ -1460,11 +1459,10 @@ impl<A: Step> RangeInclusiveIteratorImpl for ops::RangeInclusive<A> {
accum = f(accum, n)?;
}

self.exhausted = true;

if self.start == self.end {
accum = f(accum, self.start.clone())?;
}
let (n, o) = Step::backward_overflowing(self.end.clone(), 1);
let last = mem::replace(&mut self.end, n);
self.exhausted = o;
accum = f(accum, last)?;

try { accum }
}
Expand All @@ -1491,11 +1489,10 @@ impl<T: TrustedStep> RangeInclusiveIteratorImpl for ops::RangeInclusive<T> {
accum = f(accum, n)?;
}

self.exhausted = true;

if self.start == self.end {
accum = f(accum, self.start)?;
}
let (n, o) = Step::forward_overflowing(self.start, 1);
let last = mem::replace(&mut self.start, n);
self.exhausted = o;
accum = f(accum, last)?;

try { accum }
}
Expand All @@ -1520,11 +1517,10 @@ impl<T: TrustedStep> RangeInclusiveIteratorImpl for ops::RangeInclusive<T> {
accum = f(accum, n)?;
}

self.exhausted = true;

if self.start == self.end {
accum = f(accum, self.start)?;
}
let (n, o) = Step::backward_overflowing(self.end, 1);
let last = mem::replace(&mut self.end, n);
self.exhausted = o;
accum = f(accum, last)?;

try { accum }
}
Expand Down
31 changes: 31 additions & 0 deletions library/coretests/tests/iter/range.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -675,3 +675,34 @@ fn test_nonzero_range() {
(usize::MAX, Some(usize::MAX))
);
}

#[test]
fn test_range_inclusive_try_fold_state_matches_next() {
// normal range
let mut a = 1..=3;
let mut b = 1..=3;
a.try_fold((), |_, _| Some(()));
for _ in b.by_ref() {}
assert_eq!(a, b);

// overflow at the end of the type
let mut a = 250u8..=255;
let mut b = 250u8..=255;
a.try_fold((), |_, _| Some(()));
for _ in b.by_ref() {}
assert_eq!(a, b);

// try_rfold, and overflow at the start of the type
let mut a = 0u8..=5;
let mut b = 0u8..=5;
a.try_rfold((), |_, _| Some(()));
while b.next_back().is_some() {}
assert_eq!(a, b);

// early break on the last element
let mut a = 1..=3;
let mut b = 1..=3;
a.try_fold((), |_, x| if x == 3 { None } else { Some(()) });
for _ in b.by_ref() {}
assert_eq!(a, b);
}
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