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impl TrustedLen for all RangeFrom<A>, IterRangeFrom<A> #148152

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impl TrustedLen for all RangeFrom<A>, IterRangeFrom<A> #148152

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4 changes: 2 additions & 2 deletions library/core/src/iter/range.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1031,9 +1031,9 @@ impl<A: Step> Iterator for ops::RangeFrom<A> {
}
}

// Safety: See above implementation for `ops::Range<A>`
// Safety: RangeFrom::next() cannot return None
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@hkBst hkBst Oct 27, 2025

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It can if the implementation is changed to do so...

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// Safety: RangeFrom::next() cannot return None
// Safety: RangeFrom::next() never returns None

or "always returns Some". In either case, I'd like to see this reasoning expanded upon, because right now it is difficult to see why this even matters.

#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<A: TrustedStep> TrustedLen for ops::RangeFrom<A> {}
unsafe impl<A: Step> TrustedLen for ops::RangeFrom<A> {}

#[stable(feature = "fused", since = "1.26.0")]
impl<A: Step> FusedIterator for ops::RangeFrom<A> {}
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3 changes: 2 additions & 1 deletion library/core/src/range/iter.rs
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Expand Up @@ -322,8 +322,9 @@ impl<A: Step> Iterator for IterRangeFrom<A> {
}
}

// Safety: RangeFrom::next() cannot return None
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<A: TrustedStep> TrustedLen for IterRangeFrom<A> {}
unsafe impl<A: Step> TrustedLen for IterRangeFrom<A> {}

#[unstable(feature = "new_range_api", issue = "125687")]
impl<A: Step> FusedIterator for IterRangeFrom<A> {}
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