Rollup merge of rust-lang#68800 - JohnTitor:stabilize-once-with, r=Centril

Stabilize `core::iter::once_with()`

Fixes rust-lang#57581

FCP: rust-lang#57581 (comment)

r? @SimonSapin

Author: Dylan-DPC

src/libcore/iter/mod.rs

@@ -327,7 +327,7 @@ pub use self::sources::{empty, Empty};
 pub use self::sources::{from_fn, FromFn};
 #[stable(feature = "iter_once", since = "1.2.0")]
 pub use self::sources::{once, Once};
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 pub use self::sources::{once_with, OnceWith};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::sources::{repeat, Repeat};

src/libcore/iter/sources.rs

@@ -399,12 +399,12 @@ pub fn once<T>(value: T) -> Once<T> {
 ///
 /// [`once_with`]: fn.once_with.html
 #[derive(Copy, Clone, Debug)]
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 pub struct OnceWith<F> {
     gen: Option<F>,
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> Iterator for OnceWith<F> {
     type Item = A;
 
@@ -420,24 +420,24 @@ impl<A, F: FnOnce() -> A> Iterator for OnceWith<F> {
     }
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> DoubleEndedIterator for OnceWith<F> {
     fn next_back(&mut self) -> Option<A> {
         self.next()
     }
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> ExactSizeIterator for OnceWith<F> {
     fn len(&self) -> usize {
         self.gen.iter().len()
     }
 }
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 impl<A, F: FnOnce() -> A> FusedIterator for OnceWith<F> {}
 
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 
 /// Creates an iterator that lazily generates a value exactly once by invoking
@@ -458,8 +458,6 @@ unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 /// Basic usage:
 ///
 /// ```
-/// #![feature(iter_once_with)]
-///
 /// use std::iter;
 ///
 /// // one is the loneliest number
@@ -476,8 +474,6 @@ unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 /// `.foorc`:
 ///
 /// ```no_run
-/// #![feature(iter_once_with)]
-///
 /// use std::iter;
 /// use std::fs;
 /// use std::path::PathBuf;
@@ -500,7 +496,7 @@ unsafe impl<A, F: FnOnce() -> A> TrustedLen for OnceWith<F> {}
 /// }
 /// ```
 #[inline]
-#[unstable(feature = "iter_once_with", issue = "57581")]
+#[stable(feature = "iter_once_with", since = "1.43.0")]
 pub fn once_with<A, F: FnOnce() -> A>(gen: F) -> OnceWith<F> {
     OnceWith { gen: Some(gen) }
 }

src/libcore/lib.rs

@@ -87,7 +87,6 @@
 #![feature(intrinsics)]
 #![feature(try_find)]
 #![feature(is_sorted)]
-#![feature(iter_once_with)]
 #![feature(lang_items)]
 #![feature(link_llvm_intrinsics)]
 #![feature(never_type)]

src/libcore/tests/lib.rs

@@ -13,7 +13,6 @@
 #![feature(hashmap_internals)]
 #![feature(try_find)]
 #![feature(is_sorted)]
-#![feature(iter_once_with)]
 #![feature(pattern)]
 #![feature(range_is_empty)]
 #![feature(raw)]