Fix operator handling.

sdk/lib/_internal/compiler/implementation/elements/elements.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.
 
 library elements;
 
 import 'dart:uri';
 
 // TODO(ahe): Rename prefix to 'api' when VM bug is fixed.
 import '../../compiler.dart' as api_e;
@@ skipping 1843 matching lines @@
       return const SourceString(r'operator$or');
     } else if (identical(value, '-')) {
       return const SourceString(r'operator$sub');
     } else if (identical(value, 'unary-')) {
       return const SourceString(r'operator$negate');
     } else {
       return name;
     }
   }
 
-  static SourceString constructOperatorName(SourceString op, bool isUnary) {
+  static SourceString constructOperatorNameOrNull(SourceString op,
+                                                  bool isUnary) {
     String value = op.stringValue;
     if ((value === '==') ||
         (value === '~') ||
         (value === '[]') ||
         (value === '[]=') ||
         (value === '*') ||
         (value === '/') ||
         (value === '%') ||
         (value === '~/') ||
         (value === '+') ||
         (value === '<<') ||
         (value === '>>>') ||
         (value === '>>') ||
         (value === '>=') ||
         (value === '>') ||
         (value === '<=') ||
         (value === '<') ||
         (value === '&') ||
         (value === '^') ||
         (value === '|')) {
       return op;
     } else if (value === '-') {
       return isUnary ? const SourceString('unary-') : op;
     } else {
-      throw 'Unhandled operator: ${op.slowToString()}';
+      return null;
     }
   }
 
-  static SourceString mapToUserOperator(SourceString op) {
+  static SourceString constructOperatorName(SourceString op, bool isUnary) {
+    SourceString operatorName = constructOperatorNameOrNull(op, isUnary);
+    if (operatorName == null) throw 'Unhandled operator: ${op.slowToString()}';
+    else return operatorName;
+  }
+
+  static SourceString mapToUserOperatorOrNull(SourceString op) {
     String value = op.stringValue;
 
     if (identical(value, '!=')) return const SourceString('==');
     if (identical(value, '*=')) return const SourceString('*');
     if (identical(value, '/=')) return const SourceString('/');
     if (identical(value, '%=')) return const SourceString('%');
     if (identical(value, '~/=')) return const SourceString('~/');
     if (identical(value, '+=')) return const SourceString('+');
     if (identical(value, '-=')) return const SourceString('-');
     if (identical(value, '<<=')) return const SourceString('<<');
     if (identical(value, '>>=')) return const SourceString('>>');
     if (identical(value, '&=')) return const SourceString('&');
     if (identical(value, '^=')) return const SourceString('^');
     if (identical(value, '|=')) return const SourceString('|');
 
-    throw 'Unhandled operator: ${op.slowToString()}';
+    return null;
+  }
+
+  static SourceString mapToUserOperator(SourceString op) {
+    SourceString userOperator = mapToUserOperatorOrNull(op);
+    if (userOperator == null) throw 'Unhandled operator: ${op.slowToString()}';
+    else return userOperator;
   }
 
   static bool isNumberOrStringSupertype(Element element, Compiler compiler) {
     LibraryElement coreLibrary = compiler.coreLibrary;
     return (element == coreLibrary.find(const SourceString('Comparable')));
   }
 
   static bool isStringOnlySupertype(Element element, Compiler compiler) {
     LibraryElement coreLibrary = compiler.coreLibrary;
     return element == coreLibrary.find(const SourceString('Pattern'));
@@ skipping 119 matching lines @@
 
   MetadataAnnotation ensureResolved(Compiler compiler) {
     if (resolutionState == STATE_NOT_STARTED) {
       compiler.resolver.resolveMetadataAnnotation(this);
     }
     return this;
   }
 
   String toString() => 'MetadataAnnotation($value, $resolutionState)';
 }