Fix behaviour after iterator exhaustion

src/libcore/iter/range.rs

@@ -377,17 +377,23 @@ impl<A: Step> Iterator for ops::RangeInclusive<A> {
 
     #[inline]
     fn last(self) -> Option<A> {
-        Some(self.end)
+        if self.start <= self.end {
+            Some(self.end)
+        } else { None }
     }
 
     #[inline]
     fn min(self) -> Option<A> {
-        Some(self.start)
+        if self.start <= self.end {
+            Some(self.start)
+        } else { None }
     }
 
     #[inline]
     fn max(self) -> Option<A> {
-        Some(self.end)
+        if self.start <= self.end {
+            Some(self.end)
+        } else { None }
     }
 }
 

src/libcore/tests/iter.rs

@@ -1360,21 +1360,30 @@ fn test_range_max() {
 }
 
 #[test]
-fn test_range_inc_last_max() {
+fn test_range_inclusive_last_max() {
     assert_eq!((0..=20).last(), Some(20));
     assert_eq!((-20..=0).last(), Some(0));
     assert_eq!((5..=5).last(), Some(5));
+    let mut r = 10..=10;
+    r.next();
+    assert_eq!(r.last(), None);
 
     assert_eq!((0..=20).max(), Some(20));
     assert_eq!((-20..=0).max(), Some(0));
     assert_eq!((5..=5).max(), Some(5));
+    let mut r = 10..=10;
+    r.next();
+    assert_eq!(r.max(), None);
 }
 
 #[test]
-fn test_range_inc_min() {
+fn test_range_inclusive_min() {
     assert_eq!((0..=20).min(), Some(0));
     assert_eq!((-20..=0).min(), Some(-20));
     assert_eq!((5..=5).min(), Some(5));
+    let mut r = 10..=10;
+    r.next();
+    assert_eq!(r.min(), None);
 }
 
 #[test]