1 files changed, 19 insertions, 14 deletions

diff --git a/libcollections/string.rs b/libcollections/string.rs
index c84d849..306fad2 100644
--- a/libcollections/string.rs
+++ b/libcollections/string.rs
@@ -992,10 +992,12 @@ impl String {
 
     /// Shortens this `String` to the specified length.
     ///
+    /// If `new_len` is greater than the string's current length, this has no
+    /// effect.
+    ///
     /// # Panics
     ///
-    /// Panics if `new_len` > current length, or if `new_len` does not lie on a
-    /// [`char`] boundary.
+    /// Panics if `new_len` does not lie on a [`char`] boundary.
     ///
     /// [`char`]: ../../std/primitive.char.html
     ///
@@ -1013,8 +1015,10 @@ impl String {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn truncate(&mut self, new_len: usize) {
-        assert!(self.is_char_boundary(new_len));
-        self.vec.truncate(new_len)
+        if new_len <= self.len() {
+            assert!(self.is_char_boundary(new_len));
+            self.vec.truncate(new_len)
+        }
     }
 
     /// Removes the last character from the string buffer and returns it.
@@ -1037,14 +1041,13 @@ impl String {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn pop(&mut self) -> Option<char> {
-        let len = self.len();
-        if len == 0 {
-            return None;
-        }
-
-        let ch = self.char_at_reverse(len);
+        let ch = match self.chars().rev().next() {
+            Some(ch) => ch,
+            None => return None,
+        };
+        let newlen = self.len() - ch.len_utf8();
         unsafe {
-            self.vec.set_len(len - ch.len_utf8());
+            self.vec.set_len(newlen);
         }
         Some(ch)
     }
@@ -1075,11 +1078,13 @@ impl String {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn remove(&mut self, idx: usize) -> char {
-        let len = self.len();
-        assert!(idx < len);
+        let ch = match self[idx..].chars().next() {
+            Some(ch) => ch,
+            None => panic!("cannot remove a char from the end of a string"),
+        };
 
-        let ch = self.char_at(idx);
         let next = idx + ch.len_utf8();
+        let len = self.len();
         unsafe {
             ptr::copy(self.vec.as_ptr().offset(next as isize),
                       self.vec.as_mut_ptr().offset(idx as isize),