Merging upstream version 1.75.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 59 insertions, 0 deletions

diff --git a/library/core/src/iter/sources/from_coroutine.rs b/library/core/src/iter/sources/from_coroutine.rs
new file mode 100644
index 000000000..16fbca9b6
--- /dev/null
+++ b/library/core/src/iter/sources/from_coroutine.rs
@@ -0,0 +1,59 @@
+use crate::fmt;
+use crate::ops::{Coroutine, CoroutineState};
+use crate::pin::Pin;
+
+/// Creates a new iterator where each iteration calls the provided coroutine.
+///
+/// Similar to [`iter::from_fn`].
+///
+/// [`iter::from_fn`]: crate::iter::from_fn
+///
+/// # Examples
+///
+/// ```
+/// #![cfg_attr(bootstrap, feature(generators))]
+/// #![cfg_attr(not(bootstrap), feature(coroutines))]
+/// #![feature(iter_from_coroutine)]
+///
+/// let it = std::iter::from_coroutine(|| {
+///     yield 1;
+///     yield 2;
+///     yield 3;
+/// });
+/// let v: Vec<_> = it.collect();
+/// assert_eq!(v, [1, 2, 3]);
+/// ```
+#[inline]
+#[unstable(feature = "iter_from_coroutine", issue = "43122", reason = "coroutines are unstable")]
+pub fn from_coroutine<G: Coroutine<Return = ()> + Unpin>(coroutine: G) -> FromCoroutine<G> {
+    FromCoroutine(coroutine)
+}
+
+/// An iterator over the values yielded by an underlying coroutine.
+///
+/// This `struct` is created by the [`iter::from_coroutine()`] function. See its documentation for
+/// more.
+///
+/// [`iter::from_coroutine()`]: from_coroutine
+#[unstable(feature = "iter_from_coroutine", issue = "43122", reason = "coroutines are unstable")]
+#[derive(Clone)]
+pub struct FromCoroutine<G>(G);
+
+#[unstable(feature = "iter_from_coroutine", issue = "43122", reason = "coroutines are unstable")]
+impl<G: Coroutine<Return = ()> + Unpin> Iterator for FromCoroutine<G> {
+    type Item = G::Yield;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        match Pin::new(&mut self.0).resume(()) {
+            CoroutineState::Yielded(n) => Some(n),
+            CoroutineState::Complete(()) => None,
+        }
+    }
+}
+
+#[unstable(feature = "iter_from_coroutine", issue = "43122", reason = "coroutines are unstable")]
+impl<G> fmt::Debug for FromCoroutine<G> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("FromCoroutine").finish()
+    }
+}