Add extra information to FormatException.

runtime/lib/integers_patch.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.
 // Dart core library.
 
 // VM implementation of int.
 
 patch class int {
 
   static bool _isWhitespace(int codePoint) {
@@ skipping 49 matching lines @@
   static int _parse(String str) {
     int res = _tryParseSmi(str);
     if (res == null) {
       res = _native_parse(str);
     }
     return res;
   }
 
   static int _native_parse(String str) native "Integer_parse";
 
-  static int _throwFormatException(String source) {
-    throw new FormatException(source);
+  static int _throwFormatException(String source, int position) {
+    throw new FormatException("", source, position);
   }
 
   /* patch */ static int parse(String source,
                                { int radix,
                                  int onError(String str) }) {
     if (radix == null) {
       int result = _parse(source);
       if (result == null) {
         if (onError == null) {
-          throw new FormatException(source);
+          throw new FormatException("", source);
         }
         return onError(source);
       }
       return result;
     }
     return _slowParse(source, radix, onError);
   }
 
   /* patch */ const factory int.fromEnvironment(String name,
                                                 {int defaultValue})
       native "Integer_fromEnvironment";
 
   static int _slowParse(String source, int radix, int onError(String str)) {
     if (source is! String) throw new ArgumentError(source);
     if (radix is! int) throw new ArgumentError("Radix is not an integer");
     if (radix < 2 || radix > 36) {
       throw new RangeError("Radix $radix not in range 2..36");
     }
-    if (onError == null) {
-      onError = _throwFormatException;
-    }
     // Remove leading and trailing white space.
-    source = source.trim();
-    if (source.isEmpty) return onError(source);
+    int start = source._firstNonWhitespace();
+    int i = start;
+    if (onError == null) onError = (source) {
+      throw new FormatException("Invalid radix-$radix number", source, i);
+    };
+    if (start == source.length) return onError(source);
+    int end = source._lastNonWhitespace() + 1;
 
     bool negative = false;
     int result = 0;
 
     // The value 99 is used to represent a non-digit. It is too large to be
     // a digit value in any of the used bases.
     const NA = 99;
     const List<int> digits = const <int>[
       00, 01, 02, 03, 04, 05, 06, 07, 08, 09, NA, NA, NA, NA, NA, NA,  // 0x30
       NA, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,  // 0x40
       25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, NA, NA, NA, NA, NA,  // 0x50
       NA, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,  // 0x60
       25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, NA, NA, NA, NA, NA,  // 0x70
     ];
 
-    int i = 0;
     int code = source.codeUnitAt(i);
     if (code == 0x2d || code == 0x2b) { // Starts with a plus or minus-sign.
       negative = (code == 0x2d);
-      if (source.length == 1) return onError(source);
-      i = 1;
+      i++;
+      if (i == end) return onError(source);
       code = source.codeUnitAt(i);
     }
     do {
       if (code < 0x30 || code > 0x7f) return onError(source);
       int digit = digits[code - 0x30];
       if (digit >= radix) return onError(source);
       result = result * radix + digit;
       i++;
-      if (i == source.length) break;
+      if (i == end) break;
       code = source.codeUnitAt(i);
     } while (true);
     return negative ? -result : result;
   }
 }