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| -rw-r--r-- | library/core/src/iter/traits/exact_size.rs | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/library/core/src/iter/traits/exact_size.rs b/library/core/src/iter/traits/exact_size.rs index 996d62e2b4a..167db3359f2 100644 --- a/library/core/src/iter/traits/exact_size.rs +++ b/library/core/src/iter/traits/exact_size.rs @@ -13,6 +13,12 @@ /// implement it. However, you may be able to provide a more performant /// implementation than the default, so overriding it in this case makes sense. /// +/// Note that this trait is a safe trait and as such does *not* and *cannot* +/// guarantee that the returned length is correct. This means that `unsafe` +/// code **must not** rely on the correctness of [`Iterator::size_hint`]. The +/// unstable and unsafe [`TrustedLen`](super::marker::TrustedLen) trait gives +/// this additional guarantee. +/// /// [`len`]: ExactSizeIterator::len /// /// # Examples |