Fix ill-formatted error messages in analyzer.

pkg/analyzer/lib/src/generated/java_core.dart

 library java.core;
 
 const int LONG_MAX_VALUE = 0x7fffffffffffffff;
 
 final Stopwatch nanoTimeStopwatch = new Stopwatch();
 
 /**
  * Inserts the given arguments into [pattern].
  *
  *     format('Hello, {0}!', 'John') = 'Hello, John!'
  *     format('{0} are you {1}ing?', 'How', 'do') = 'How are you doing?'
  *     format('{0} are you {1}ing?', 'What', 'read') = 'What are you reading?'
  */
 String format(String pattern,
     [arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7]) {
   return formatList(pattern, [arg0, arg1, arg2, arg3, arg4, arg5, arg6, arg7]);
 }
 
 /**
  * Inserts the given [args] into [pattern].
  *
  *     format('Hello, {0}!', ['John']) = 'Hello, John!'
  *     format('{0} are you {1}ing?', ['How', 'do']) = 'How are you doing?'
  *     format('{0} are you {1}ing?', ['What', 'read']) = 'What are you reading?'
  */
 String formatList(String pattern, List<Object> arguments) {
   if (arguments == null || arguments.isEmpty) {
+    assert(!pattern.contains(new RegExp(r'\{(\d+)\}')));
     return pattern;
   }
   return pattern.replaceAllMapped(new RegExp(r'\{(\d+)\}'), (match) {
     String indexStr = match.group(1);
     int index = int.parse(indexStr);
     Object arg = arguments[index];
+    assert(arg != null);
     return arg != null ? arg.toString() : null;
   });
 }
 
 bool javaCollectionContainsAll(Iterable list, Iterable c) {
   return c.fold(true, (bool prev, e) => prev && list.contains(e));
 }
 
 javaListSet(List list, int index, newValue) {
   var oldValue = list[index];
@@ skipping 385 matching lines @@
 
 class UnsupportedOperationException extends JavaException {
   UnsupportedOperationException([message = ""]) : super(message);
 }
 
 class URISyntaxException implements Exception {
   final String message;
   URISyntaxException(this.message);
   String toString() => "URISyntaxException: $message";
 }