Fix doc links in core::iter::sources

Author: WaffleLapkin

library/core/src/iter/sources/from_fn.rs

@@ -15,6 +15,7 @@ use crate::fmt;
 /// how the iterator is used, this may require specifying the [`move`] keyword on the closure.
 ///
 /// [`move`]: ../../std/keyword.move.html
+/// [`FusedIterator`]: crate::iter::FusedIterator
 ///
 /// # Examples
 ///

library/core/src/iter/sources/once_with.rs

@@ -11,6 +11,7 @@ use crate::iter::{FusedIterator, TrustedLen};
 /// Unlike [`once()`], this function will lazily generate the value on request.
 ///
 /// [`chain()`]: Iterator::chain
+/// [`once()`]: crate::iter::once
 ///
 /// # Examples
 ///

library/core/src/iter/sources/repeat.rs

@@ -11,6 +11,8 @@ use crate::iter::{FusedIterator, TrustedLen};
 /// or if you do not want to keep the repeated element in memory, you can
 /// instead use the [`repeat_with()`] function.
 ///
+/// [`repeat_with()`]: crate::iter::repeat_with
+///
 /// # Examples
 ///
 /// Basic usage:

library/core/src/iter/sources/repeat_with.rs

@@ -16,6 +16,7 @@ use crate::iter::{FusedIterator, TrustedLen};
 /// If you need `repeat_with()` to return a [`DoubleEndedIterator`],
 /// please open a GitHub issue explaining your use case.
 ///
+/// [`repeat()`]: crate::iter::repeat
 /// [`DoubleEndedIterator`]: crate::iter::DoubleEndedIterator
 ///
 /// # Examples