Deprecated for the std: link to the documentation.

Strictly similar to what is done for our free function `zip`.

src/lib.rs

@@ -2426,7 +2426,10 @@ pub trait Itertools: Iterator {
     /// assert_eq!((0..10).fold1(|x, y| x + y).unwrap_or(0), 45);
     /// assert_eq!((0..0).fold1(|x, y| x * y), None);
     /// ```
-    #[deprecated(since = "0.10.2", note = "Use `Iterator::reduce` instead")]
+    #[deprecated(
+        note = "Use [`Iterator::reduce`](https://doc.rust-lang.org/std/iter/trait.Iterator.html#method.reduce) instead",
+        since = "0.10.2"
+    )]
     fn fold1<F>(mut self, f: F) -> Option<Self::Item>
     where
         F: FnMut(Self::Item, Self::Item) -> Self::Item,

src/sources.rs

@@ -41,7 +41,10 @@ use std::mem;
 ///                         vec![1, 1, 2, 3, 5, 8, 13, 21]);
 /// assert_eq!(fibonacci.last(), Some(2_971_215_073))
 /// ```
-#[deprecated(note = "Use std from_fn() instead", since = "0.13.0")]
+#[deprecated(
+    note = "Use [std::iter::from_fn](https://doc.rust-lang.org/std/iter/fn.from_fn.html) instead",
+    since = "0.13.0"
+)]
 pub fn unfold<A, St, F>(initial_state: St, f: F) -> Unfold<St, F>
 where
     F: FnMut(&mut St) -> Option<A>,
@@ -62,7 +65,10 @@ where
 /// See [`unfold`](crate::unfold) for more information.
 #[derive(Clone)]
 #[must_use = "iterators are lazy and do nothing unless consumed"]
-#[deprecated(note = "Use std from_fn() instead", since = "0.13.0")]
+#[deprecated(
+    note = "Use [std::iter::FromFn](https://doc.rust-lang.org/std/iter/struct.FromFn.html) instead",
+    since = "0.13.0"
+)]
 pub struct Unfold<St, F> {
     f: F,
     /// Internal state that will be passed to the closure on the next iteration