Add iterator method specialisations to Range*

src/libcore/iter/range.rs

@@ -251,6 +251,13 @@ impl<A: Step> Iterator for ops::Range<A> {
         self.start = self.end.clone();
         None
     }
+
+    #[inline]
+    fn max(self) -> Option<A> {
+        if self.start != self.end {
+            Some(self.end.sub_one())
+        } else { None }
+    }
 }
 
 // These macros generate `ExactSizeIterator` impls for various range types.
@@ -305,6 +312,11 @@ impl<A: Step> Iterator for ops::RangeFrom<A> {
         self.start = plus_n.add_one();
         Some(plus_n)
     }
+
+    #[inline]
+    fn min(self) -> Option<A> {
+        Some(self.start)
+    }
 }
 
 #[unstable(feature = "fused", issue = "35602")]
@@ -367,6 +379,21 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
         self.end.replace_zero();
         None
     }
+
+    #[inline]
+    fn last(self) -> Option<A> {
+        Some(self.end)
+    }
+
+    #[inline]
+    fn min(self) -> Option<A> {
+        Some(self.start)
+    }
+
+    #[inline]
+    fn max(self) -> Option<A> {
+        Some(self.end)
+    }
 }
 
 #[unstable(feature = "inclusive_range", reason = "recently added, follows RFC", issue = "28237")]

src/libcore/tests/iter.rs

@@ -1352,6 +1352,38 @@ fn test_range_step() {
     assert_eq!((isize::MIN..isize::MAX).step_by(1).size_hint(), (usize::MAX, Some(usize::MAX)));
 }
 
+#[test]
+fn test_range_max() {
+    assert_eq!((0..100).max(), Some(99));
+    assert_eq!((-20..-10).max(), Some(-11));
+    assert_eq!((1..1).max(), None);
+}
+
+#[test]
+fn test_range_from_min() {
+    assert_eq!((0..).min(), Some(0));
+    assert_eq!((-20..).min(), Some(-20));
+    assert_eq!((20..).min(), Some(20));
+}
+
+#[test]
+fn test_range_inc_last_max() {
+    assert_eq!((0..=20).last(), Some(20));
+    assert_eq!((-20..=0).last(), Some(0));
+    assert_eq!((5..=5).last(), Some(5));
+
+    assert_eq!((0..=20).max(), Some(20));
+    assert_eq!((-20..=0).max(), Some(0));
+    assert_eq!((5..=5).max(), Some(5));
+}
+
+#[test]
+fn test_range_inc_min() {
+    assert_eq!((0..=20).min(), Some(0));
+    assert_eq!((-20..=0).min(), Some(-20));
+    assert_eq!((5..=5).min(), Some(5));
+}
+
 #[test]
 fn test_repeat() {
     let mut it = repeat(42);