Add a test for char ranges

src/libcore/tests/iter.rs

@@ -1932,6 +1932,16 @@ fn test_range() {
     );
 }
 
+#[test]
+fn test_char_range() {
+    use std::char;
+    assert!(('\0'..=char::MAX).eq((0..=char::MAX as u32).filter_map(char::from_u32)));
+    assert!(('\0'..=char::MAX).rev().eq((0..=char::MAX as u32).filter_map(char::from_u32).rev()));
+
+    assert_eq!(('\u{D7FF}'..='\u{E000}').count(), 2);
+    assert_eq!(('\u{D7FF}'..'\u{E000}').count(), 1);
+}
+
 #[test]
 fn test_range_exhaustion() {
     let mut r = 10..10;