Better messages for optimized index errors.

sdk/lib/_internal/compiler/js_lib/js_string.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of _interceptors;
 
 /**
  * The interceptor class for [String]. The compiler recognizes this
  * class as an interceptor, and changes references to [:this:] to
  * actually use the receiver of the method, which is generated as an extra
  * argument added to each member.
  */
 class JSString extends Interceptor implements String, JSIndexable {
   const JSString();
 
   int codeUnitAt(int index) {
-    if (index is !int) throw new ArgumentError(index);
-    if (index < 0) throw new RangeError.value(index);
-    if (index >= length) throw new RangeError.value(index);
+    if (index is !int) throw diagnoseIndexError(this, index);
+    if (index < 0) throw diagnoseIndexError(this, index);
+    if (index >= length) throw diagnoseIndexError(this, index);
     return JS('JSUInt31', r'#.charCodeAt(#)', this, index);
   }
 
   Iterable<Match> allMatches(String string, [int start = 0]) {
     checkString(string);
     checkInt(start);
     if (0 > start || start > string.length) {
       throw new RangeError.range(start, 0, string.length);
     }
     return allMatchesInStringUnchecked(this, string, start);
   }
 
   Match matchAsPrefix(String string, [int start = 0]) {
     if (start < 0 || start > string.length) {
       throw new RangeError.range(start, 0, string.length);
     }
     if (start + this.length > string.length) return null;
     // TODO(lrn): See if this can be optimized.
     for (int i = 0; i < this.length; i++) {
       if (string.codeUnitAt(start + i) != this.codeUnitAt(i)) {
         return null;
       }
     }
     return new StringMatch(start, string, this);
   }
 
   String operator +(String other) {
-    if (other is !String) throw new ArgumentError(other);
+    if (other is !String) throw new ArgumentError.value(other);
     return JS('String', r'# + #', this, other);
   }
 
   bool endsWith(String other) {
     checkString(other);
     int otherLength = other.length;
     if (otherLength > length) return false;
     return other == substring(length - otherLength);
   }
 
@@ skipping 404 matching lines @@
     hash = 0x1fffffff & (hash + ((0x03ffffff & hash) <<  3));
     hash = JS('int', '# ^ (# >> 11)', hash, hash);
     return 0x1fffffff & (hash + ((0x00003fff & hash) << 15));
   }
 
   Type get runtimeType => String;
 
   int get length => JS('int', r'#.length', this);
 
   String operator [](int index) {
-    if (index is !int) throw new ArgumentError(index);
-    if (index >= length || index < 0) throw new RangeError.value(index);
+    if (index is !int) throw diagnoseIndexError(this, index);
+    if (index >= length || index < 0) throw diagnoseIndexError(this, index);
     return JS('String', '#[#]', this, index);
   }
 }