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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:41 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:19:41 +0000 |
| commit | 4f9fe856a25ab29345b90e7725509e9ee38a37be (patch) | |
| tree | e4ffd8a9374cae7b21f7cbfb352927e0e074aff6 /library/core/src/iter/traits/exact_size.rs | |
| parent | Adding upstream version 1.68.2+dfsg1. (diff) | |
| download | rustc-4f9fe856a25ab29345b90e7725509e9ee38a37be.tar.xz rustc-4f9fe856a25ab29345b90e7725509e9ee38a37be.zip | |
Adding upstream version 1.69.0+dfsg1.upstream/1.69.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
| -rw-r--r-- | library/core/src/iter/traits/exact_size.rs | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/library/core/src/iter/traits/exact_size.rs b/library/core/src/iter/traits/exact_size.rs index 1757e37ec..908830d8a 100644 --- a/library/core/src/iter/traits/exact_size.rs +++ b/library/core/src/iter/traits/exact_size.rs @@ -21,6 +21,16 @@ /// /// [`len`]: ExactSizeIterator::len /// +/// # When *shouldn't* an adapter be `ExactSizeIterator`? +/// +/// If an adapter makes an iterator *longer*, then it's usually incorrect for +/// that adapter to implement `ExactSizeIterator`. The inner exact-sized +/// iterator might already be `usize::MAX`-long, and thus the length of the +/// longer adapted iterator would no longer be exactly representable in `usize`. +/// +/// This is why [`Chain<A, B>`](crate::iter::Chain) isn't `ExactSizeIterator`, +/// even when `A` and `B` are both `ExactSizeIterator`. +/// /// # Examples /// /// Basic usage: |