dart2js cps: Generate increment and compound operators.

pkg/compiler/lib/src/cps_ir/builtin_operator.dart

 // Copyright (c) 2015, 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 builtin_operator;
 // This is shared by the CPS and Tree IRs.
 // Both cps_ir_nodes and tree_ir_nodes import and re-export this file.
 
 /// An operator supported natively in the CPS and Tree IRs using the
 /// `ApplyBuiltinOperator` instructions.
 ///
@@ skipping 140 matching lines @@
   ///
   /// Precondition: Argument is a JavaScript Array.
   IsUnmodifiableJSArray,
 
   // TODO(sra): Remove this and replace with IsFalsy(IsUnmodifiableArray(x)).
   IsModifiableJSArray,
 }
 
 /// A method supported natively in the CPS and Tree IRs using the
 /// `ApplyBuiltinMethod` instructions.
-/// 
+///
 /// These methods all operate on a distinguished 'object' argument, and
 /// take zero or more additional arguments.
-/// 
+///
 /// These methods may mutate and depend on the state of the object argument,
 /// but may not depend on or mutate any other state. An exception is thrown
 /// if the object is null, but otherwise they cannot throw or diverge.
 enum BuiltinMethod {
   /// Add an item to a native list.
-  /// 
+  ///
   /// Takes any number of arguments, each argument will be added to the
   /// list on the order given (as per the JS `push` method).
-  /// 
+  ///
   /// Compiles to `object.push(x1, ..., xN)`.
   Push,
 
   /// Remove and return the last item from a native list.
-  /// 
+  ///
   /// Takes no arguments.
-  /// 
+  ///
   /// Compiles to `object.pop()`.
   Pop,
 }
+
+/// True for the built-in operators that may be used in a compound assignment.
+bool isCompoundableOperator(BuiltinOperator operator) {
+  switch(operator) {
+    case BuiltinOperator.NumAdd:
+    case BuiltinOperator.NumSubtract:
+    case BuiltinOperator.NumMultiply:
+    case BuiltinOperator.NumDivide:
+    case BuiltinOperator.NumRemainder:
+    case BuiltinOperator.StringConcatenate:
+      return true;
+    default:
+      return false;
+  }
+}