New upstream version 1.48.0~beta.8+dfsg1

[rustc.git] / library / core / src / iter / traits / marker.rs

diff --git a/library/core/src/iter/traits/marker.rs b/library/core/src/iter/traits/marker.rs
index 3c893c039923ead483300501fbf4d8046b60f2e3..0900676146c0d7c63dd590bf1d96da2954dbecc1 100644 (file)
--- a/library/core/src/iter/traits/marker.rs
+++ b/library/core/src/iter/traits/marker.rs
@@ -2,14 +2,13 @@
 ///
 /// Calling next on a fused iterator that has returned `None` once is guaranteed
 /// to return [`None`] again. This trait should be implemented by all iterators
-/// that behave this way because it allows optimizing [`Iterator::fuse`].
+/// that behave this way because it allows optimizing [`Iterator::fuse()`].
 ///
 /// Note: In general, you should not use `FusedIterator` in generic bounds if
-/// you need a fused iterator. Instead, you should just call [`Iterator::fuse`]
+/// you need a fused iterator. Instead, you should just call [`Iterator::fuse()`]
 /// on the iterator. If the iterator is already fused, the additional [`Fuse`]
 /// wrapper will be a no-op with no performance penalty.
 ///
-/// [`Iterator::fuse`]: crate::iter::Iterator::fuse
 /// [`Fuse`]: crate::iter::Fuse
 #[stable(feature = "fused", since = "1.26.0")]
 #[rustc_unsafe_specialization_marker]
@@ -24,21 +23,34 @@ impl<I: FusedIterator + ?Sized> FusedIterator for &mut I {}
 /// (lower bound is equal to upper bound), or the upper bound is [`None`].
 /// The upper bound must only be [`None`] if the actual iterator length is
 /// larger than [`usize::MAX`]. In that case, the lower bound must be
-/// [`usize::MAX`], resulting in a [`.size_hint`] of `(usize::MAX, None)`.
+/// [`usize::MAX`], resulting in a [`Iterator::size_hint()`] of
+/// `(usize::MAX, None)`.
 ///
 /// The iterator must produce exactly the number of elements it reported
 /// or diverge before reaching the end.
 ///
 /// # Safety
 ///
-/// This trait must only be implemented when the contract is upheld.
-/// Consumers of this trait must inspect [`.size_hint`]’s upper bound.
+/// This trait must only be implemented when the contract is upheld. Consumers
+/// of this trait must inspect [`Iterator::size_hint()`]’s upper bound.
 ///
 /// [`usize::MAX`]: crate::usize::MAX
-/// [`.size_hint`]: crate::iter::Iterator::size_hint
 #[unstable(feature = "trusted_len", issue = "37572")]
 #[rustc_unsafe_specialization_marker]
 pub unsafe trait TrustedLen: Iterator {}
 
 #[unstable(feature = "trusted_len", issue = "37572")]
 unsafe impl<I: TrustedLen + ?Sized> TrustedLen for &mut I {}
+
+/// An iterator that when yielding an item will have taken at least one element
+/// from its underlying [`SourceIter`].
+///
+/// Calling [`next()`] guarantees that at least one value of the iterator's underlying source
+/// has been moved out and the result of the iterator chain could be inserted in its place,
+/// assuming structural constraints of the source allow such an insertion.
+/// In other words this trait indicates that an iterator pipeline can be collected in place.
+///
+/// [`SourceIter`]: crate::iter::SourceIter
+/// [`next()`]: Iterator::next
+#[unstable(issue = "none", feature = "inplace_iteration")]
+pub unsafe trait InPlaceIterable: Iterator {}