Off by one error in str::index_mut (specifically) for RangeToInclusive (specifically) · Issue #50002 · rust-lang/rust (original) (raw)
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Description
Caught while fleshing out a much beefier test suite for SliceIndex, which I plan to submit as a PR. (this Issue is here just in case that PR never happens).
| fn index_mut(self, slice: &mut str) -> &mut Self::Output { |
|---|
| assert!(self.end != usize::max_value(), |
| "attempted to index str up to maximum usize"); |
| if slice.is_char_boundary(self.end) { |
| unsafe { self.get_unchecked_mut(slice) } |
| } else { |
| super::slice_error_fail(slice, 0, self.end + 1) |
| } |
| } |
The unicode character boundary check here should be looking at self.end + 1. Better yet, the method could just delegate to RangeTo instead. (note: it can't delegate to get_mut here without NLL, which seems to be a leading factor as to how this function ended up this way)