Better size_hint and documentation

Author: slerpyyy

library/core/src/iter/adapters/dedup.rs

@@ -50,7 +50,9 @@ where
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        (0, self.inner.size_hint().1)
+        let min = self.last.as_ref().map(|_| 1).unwrap_or(0);
+        let max = self.inner.size_hint().1;
+        (min, max)
     }
 }
 
@@ -105,7 +107,9 @@ where
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        (0, self.inner.size_hint().1)
+        let min = self.last.as_ref().map(|_| 1).unwrap_or(0);
+        let max = self.inner.size_hint().1;
+        (min, max)
     }
 }
 
@@ -161,6 +165,8 @@ where
     }
 
     fn size_hint(&self) -> (usize, Option<usize>) {
-        (0, self.inner.size_hint().1)
+        let min = self.last.as_ref().map(|_| 1).unwrap_or(0);
+        let max = self.inner.size_hint().1;
+        (min, max)
     }
 }

library/core/src/iter/traits/iterator.rs

@@ -1693,6 +1693,9 @@ pub trait Iterator {
     /// Removes all but the first of consecutive elements in the iterator according to the
     /// [`PartialEq`] trait implementation.
     ///
+    /// For an iterator yielding infinitely many consecutive duplicates,
+    /// this may result in an infinite loop.
+    ///
     /// If the iterator is sorted, this removes all duplicates.
     ///
     /// # Examples
@@ -1726,6 +1729,9 @@ pub trait Iterator {
     /// The `same_bucket` function is passed a references to two elements from the iterator and
     /// must determine if the elements compare equal.
     ///
+    /// For an iterator yielding infinitely many consecutive duplicates,
+    /// this may result in an infinite loop.
+    ///
     /// If the iterator is sorted, this removes all duplicates.
     ///
     /// # Examples
@@ -1756,6 +1762,9 @@ pub trait Iterator {
     /// Removes all but the first of consecutive elements in the iterator that
     /// resolve to the same key.
     ///
+    /// For an iterator yielding infinitely many consecutive duplicates,
+    /// this may result in an infinite loop.
+    ///
     /// If the iterator is sorted, this removes all duplicates.
     ///
     /// # Examples