---

yaml
---
r: 276541
b: refs/heads/try
c: f621193
h: refs/heads/master
i:
  276539: 05dcd25

Author: bluss

[refs]

@@ -1,7 +1,7 @@
 ---
 refs/heads/master: 6dbb0e86aec11050480beb76eade6fb805010ba7
 refs/heads/snap-stage3: 235d77457d80b549dad3ac36d94f235208a1eafb
-refs/heads/try: 80e7a1be359fc0de4eb17056230ae2fc130b7090
+refs/heads/try: f621193e5ea7ac54fcd37f0e730e955fd9f61200
 refs/tags/release-0.1: 1f5c5126e96c79d22cb7862f75304136e204f105
 refs/tags/release-0.2: c870d2dffb391e14efb05aa27898f1f6333a9596
 refs/tags/release-0.3: b5f0d0f648d9a6153664837026ba1be43d3e2503

branches/try/src/libcore/str/mod.rs

@@ -1892,7 +1892,10 @@ impl StrExt for str {
 
     #[inline]
     fn is_char_boundary(&self, index: usize) -> bool {
-        if index == self.len() { return true; }
+        // 0 and len are always ok.
+        // Test for 0 explicitly so that it can optimize out the check
+        // easily and skip reading string data for that case.
+        if index == 0 || index == self.len() { return true; }
         match self.as_bytes().get(index) {
             None => false,
             Some(&b) => b < 128 || b >= 192,