WIP: Compute constant expressions in resolution.

pkg/compiler/lib/src/js_backend/constant_system_javascript.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 dart2js.constant_system.js;
 
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../constant_system_dart.dart';
 import '../dart_types.dart';
-import '../elements/elements.dart' show ClassElement;
+import '../elements/elements.dart' show ClassElement, FieldElement;
 import '../tree/tree.dart' show DartString, LiteralDartString;
 import 'js_backend.dart';
 
 const JAVA_SCRIPT_CONSTANT_SYSTEM = const JavaScriptConstantSystem();
 
 class JavaScriptBitNotOperation extends BitNotOperation {
   const JavaScriptBitNotOperation();
 
   ConstantValue fold(ConstantValue constant) {
     if (JAVA_SCRIPT_CONSTANT_SYSTEM.isInt(constant)) {
@@ skipping 163 matching lines @@
   final greater = const GreaterOperation();
   final identity = const JavaScriptIdentityOperation();
   final lessEqual = const LessEqualOperation();
   final less = const LessOperation();
   final modulo =
       const JavaScriptBinaryArithmeticOperation(const ModuloOperation());
   final multiply =
       const JavaScriptBinaryArithmeticOperation(const MultiplyOperation());
   final negate = const JavaScriptNegateOperation();
   final not = const NotOperation();
+  final notEqual = const NotEqualsOperation();
   final shiftLeft =
       const JavaScriptBinaryBitOperation(const ShiftLeftOperation());
   final shiftRight = const JavaScriptShiftRightOperation();
   final subtract =
       const JavaScriptBinaryArithmeticOperation(const SubtractOperation());
   final truncatingDivide = const JavaScriptBinaryArithmeticOperation(
       const TruncatingDivideOperation());
   final codeUnitAt = const CodeUnitAtRuntimeOperation();
 
   const JavaScriptConstantSystem();
@@ skipping 54 matching lines @@
     return new ListConstantValue(type, values);
   }
 
   @override
   ConstantValue createType(Compiler compiler, DartType type) {
     return new TypeConstantValue(
         type,
         compiler.backend.typeImplementation.computeType(compiler.resolution));
   }
 
+  @override
+  ConstantValue createSymbol(Compiler compiler, String text) {
+    InterfaceType type = compiler.symbolClass.rawType;
+    ConstantValue argument = createString(new DartString.literal(text));
+    Map<FieldElement, ConstantValue> fields = <FieldElement, ConstantValue>{};
+    compiler.symbolImplementationClass.forEachInstanceField(
+        (ClassElement enclosingClass, FieldElement field) {
+      fields[field] = argument;
+    });
+    assert(fields.length == 1);
+    return new ConstructedConstantValue(type, fields);
+  }
+
   // Integer checks don't verify that the number is not -0.0.
   bool isInt(ConstantValue constant) => constant.isInt || constant.isMinusZero;
   bool isDouble(ConstantValue constant)
       => constant.isDouble && !constant.isMinusZero;
   bool isString(ConstantValue constant) => constant.isString;
   bool isBool(ConstantValue constant) => constant.isBool;
   bool isNull(ConstantValue constant) => constant.isNull;
 
   bool isSubtype(DartTypes types, DartType s, DartType t) {
     // At runtime, an integer is both an integer and a double: the
@@ skipping 94 matching lines @@
       result.add(keyList);
     } else {
       // Add the keys individually to avoid generating an unused list constant
       // for the keys.
       result.addAll(keys);
     }
     result.addAll(values);
     return result;
   }
 }