Remove DartString from constants.

pkg/compiler/lib/src/constant_system_dart.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.dart;
 
 import 'constants/constant_system.dart';
 import 'constants/values.dart';
 import 'common_elements.dart' show CommonElements;
 import 'elements/types.dart';
-import 'tree/dartstring.dart' show DartString;
 
 const DART_CONSTANT_SYSTEM = const DartConstantSystem();
 
 class BitNotOperation implements UnaryOperation {
   final String name = '~';
   const BitNotOperation();
   ConstantValue fold(ConstantValue constant) {
     if (constant.isInt) {
       IntConstantValue intConstant = constant;
       return DART_CONSTANT_SYSTEM.createInt(~intConstant.primitiveValue);
@@ skipping 225 matching lines @@
       int result = leftInt.primitiveValue + rightInt.primitiveValue;
       return DART_CONSTANT_SYSTEM.createInt(result);
     } else if (left.isNum && right.isNum) {
       NumConstantValue leftNum = left;
       NumConstantValue rightNum = right;
       double result = leftNum.primitiveValue + rightNum.primitiveValue;
       return DART_CONSTANT_SYSTEM.createDouble(result);
     } else if (left.isString && right.isString) {
       StringConstantValue leftString = left;
       StringConstantValue rightString = right;
-      DartString result = new DartString.concat(
-          leftString.primitiveValue, rightString.primitiveValue);
+      String result = leftString.primitiveValue + rightString.primitiveValue;
       return DART_CONSTANT_SYSTEM.createString(result);
     } else {
       return null;
     }
   }
 
   apply(left, right) => left + right;
 }
 
 abstract class RelationalNumOperation implements BinaryOperation {
@@ skipping 93 matching lines @@
   ConstantValue fold(ConstantValue left, ConstantValue right) => null;
   apply(left, right) => left.codeUnitAt(right);
 }
 
 class CodeUnitAtRuntimeOperation extends CodeUnitAtOperation {
   const CodeUnitAtRuntimeOperation();
   IntConstantValue fold(ConstantValue left, ConstantValue right) {
     if (left.isString && right.isInt) {
       StringConstantValue stringConstant = left;
       IntConstantValue indexConstant = right;
-      DartString dartString = stringConstant.primitiveValue;
+      String string = stringConstant.primitiveValue;
       int index = indexConstant.primitiveValue;
-      if (index < 0 || index >= dartString.length) return null;
-      String string = dartString.slowToString();
+      if (index < 0 || index >= string.length) return null;
       int value = string.codeUnitAt(index);
       return DART_CONSTANT_SYSTEM.createInt(value);
     }
     return null;
   }
 }
 
 class UnfoldedUnaryOperation implements UnaryOperation {
   final String name;
   const UnfoldedUnaryOperation(this.name);
@@ skipping 38 matching lines @@
 
   const DartConstantSystem();
 
   @override
   IntConstantValue createInt(int i) => new IntConstantValue(i);
 
   @override
   DoubleConstantValue createDouble(double d) => new DoubleConstantValue(d);
 
   @override
-  StringConstantValue createString(DartString string) {
+  StringConstantValue createString(String string) {
     return new StringConstantValue(string);
   }
 
   @override
   BoolConstantValue createBool(bool value) => new BoolConstantValue(value);
 
   @override
   NullConstantValue createNull() => new NullConstantValue();
 
   @override
@@ skipping 21 matching lines @@
   bool isInt(ConstantValue constant) => constant.isInt;
   bool isDouble(ConstantValue constant) => constant.isDouble;
   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) {
     return types.isSubtype(s, t);
   }
 }