fix i32 distance overflow in range length and membership#200
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fix i32 distance overflow in range length and membership#200metsw24-max wants to merge 1 commit into
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Summary: **Wrong length and membership for ranges spanning the full i32 range** `Range::length` and `is_in` compute `stop - start` with `wrapping_sub` in `i32` and then widen with `as u64`. Once the span passes `i32::MAX` the subtraction wraps to a negative value that sign-extends into a bogus `u64`, so `len(range(-2147483648, 2147483647, 1000))` reports 1271310320 rather than 4294968 and `5 in range(-2147483648, 2147483647, 7)` comes back False. Doing the distance and step-magnitude maths in `i64` (the way `rem_range_at_iter` already does) keeps the values honest and reads a bit more obviously correct. X-link: facebook/starlark-rust#200 Reviewed By: IanChilds Differential Revision: D107970420 Pulled By: JakobDegen fbshipit-source-id: fc3dc13e9c35cc1ec088450894ffaf28aefc98dc
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Wrong length and membership for ranges spanning the full i32 range
Range::lengthandis_incomputestop - startwithwrapping_subini32and then widen withas u64. Once the span passesi32::MAXthe subtraction wraps to a negative value that sign-extends into a bogusu64, solen(range(-2147483648, 2147483647, 1000))reports 1271310320 rather than 4294968 and5 in range(-2147483648, 2147483647, 7)comes back False. Doing the distance and step-magnitude maths ini64(the wayrem_range_at_iteralready does) keeps the values honest and reads a bit more obviously correct.