Make RangeError.toString use the name field that it inherits from ArgumentError.

sdk/lib/core/errors.dart

Index: sdk/lib/core/errors.dart
diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
index 0ac18808e643191f51e96665a57656df8ad4e2bf..0244ea91753d4e98bf7f9d9ff093520e27a22b5d 100644
--- a/sdk/lib/core/errors.dart
+++ b/sdk/lib/core/errors.dart
@@ -157,7 +157,7 @@ class ArgumentError extends Error {
    */
   ArgumentError.value(value,
                       [String this.name,
-                       String this.message = "Invalid argument"])
+                       String this.message])
       : invalidValue = value,
         _hasValue = true;
 
@@ -170,19 +170,22 @@ class ArgumentError extends Error {
   ArgumentError.notNull([String name])
       : this.value(null, name, "Must not be null");
 
+  // Helper functions for toString overridden in subclasses.
+  String get _errorName => "Invalid argument${name == null ? "(s)" : ""}";

[Søren Gjesse, 2015/01/27 15:27:59]

Maybe use ''s for either the outer string or the strings in the ${} expression.

+  String get _errorExplanation => "";
+
   String toString() {
-    if (!_hasValue) {
-      var result = "Invalid arguments(s)";
-      if (message != null) {
-        result = "$result: $message";
-      }
-      return result;
-    }
     String nameString = "";
     if (name != null) {
       nameString = " ($name)";
     }
-    return "$message$nameString: ${Error.safeToString(invalidValue)}";
+    var message = this.message == null ? "" : ": ${this.message}";
+    String prefix = "$_errorName$nameString$message";
+    if (invalidValue == null) return prefix;
+    // If we know the invalid value, we can try to describe the problem.
+    String explanation = _errorExplanation;
+    String errorValue = Error.safeToString(invalidValue);
+    return "$prefix$explanation: $errorValue";
   }
 }
 
@@ -274,7 +277,7 @@ class RangeError extends ArgumentError {
    * `[]` that accepts an index if `0 <= index < length`.
    *
    * If [length] is provided, it is used as the length of the indexable object,
-   * otherwise the length is found as `idexable.length`.
+   * otherwise the length is found as `indexable.length`.
    */
   static void checkValidIndex(int index, var indexable,
                               [String name, int length, String message]) {
@@ -320,9 +323,9 @@ class RangeError extends ArgumentError {
     if (value < 0) throw new RangeError.range(value, 0, null, name, message);
   }
 
-  String toString() {
-    if (!_hasValue) return "RangeError: $message";
-    String value = Error.safeToString(invalidValue);
+  String get _errorName => "RangeError";
+  String get _errorExplanation {
+    assert(_hasValue);
     String explanation = "";
     if (start == null) {
       if (end != null) {
@@ -332,14 +335,14 @@ class RangeError extends ArgumentError {
     } else if (end == null) {
       explanation = ": Not greater than or equal to $start";
     } else if (end > start) {
-      explanation = ": Not in range $start..$end, inclusive.";
+      explanation = ": Not in range $start..$end, inclusive";
     } else if (end < start) {
       explanation = ": Valid value range is empty";
     } else {
       // end == start.
       explanation = ": Only valid value is $start";
     }
-    return "RangeError: $message ($value)$explanation";
+    return explanation;
   }
 }
 
@@ -376,14 +379,15 @@ class IndexError extends ArgumentError implements RangeError {
   int get start => 0;
   int get end => length - 1;
 
-  String toString() {
+  String get _errorName => "RangeError";
+  String get _errorExplanation {
     assert(_hasValue);
     String target = Error.safeToString(indexable);
-    var explanation = "index should be less than $length";
+    var explanation = ": index should be less than $length";
     if (invalidValue < 0) {
-      explanation = "index must not be negative";
+      explanation = ": index must not be negative";
     }
-    return "RangeError: $message ($target[$invalidValue]): $explanation";
+    return explanation;
   }
 }