Implement TrustedLen for Take<Repeat> and Take<RangeFrom>

src/libcore/iter/mod.rs

@@ -2322,6 +2322,9 @@ impl<I> ExactSizeIterator for Take<I> where I: ExactSizeIterator {}
 #[unstable(feature = "fused", issue = "35602")]
 impl<I> FusedIterator for Take<I> where I: FusedIterator {}
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<I: TrustedLen> TrustedLen for Take<I> {}
+
 /// An iterator to maintain state while iterating another iterator.
 ///
 /// This `struct` is created by the [`scan`] method on [`Iterator`]. See its

src/libcore/iter/range.rs

@@ -325,6 +325,9 @@ impl<A: Step> Iterator for ops::RangeFrom<A> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<A: Step> FusedIterator for ops::RangeFrom<A> {}
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<A: Step> TrustedLen for ops::RangeFrom<A> {}
+
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]
 impl<A: Step> Iterator for ops::RangeInclusive<A> {
     type Item = A;

src/libcore/iter/sources.rs

@@ -44,6 +44,9 @@ impl<A: Clone> DoubleEndedIterator for Repeat<A> {
 #[unstable(feature = "fused", issue = "35602")]
 impl<A: Clone> FusedIterator for Repeat<A> {}
 
+#[unstable(feature = "trusted_len", issue = "37572")]
+unsafe impl<A: Clone> TrustedLen for Repeat<A> {}
+
 /// Creates a new iterator that endlessly repeats a single element.
 ///
 /// The `repeat()` function repeats a single value over and over and over and