Remove DartString from constants.

pkg/compiler/lib/src/ssa/optimize.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.
 
 import '../common/codegen.dart' show CodegenRegistry, CodegenWorkItem;
 import '../common/names.dart' show Selectors;
 import '../common/tasks.dart' show CompilerTask;
 import '../compiler.dart' show Compiler;
 import '../constants/constant_system.dart';
 import '../constants/values.dart';
 import '../common_elements.dart' show CommonElements;
 import '../elements/elements.dart'
     show ClassElement, FieldElement, MethodElement;
 import '../elements/entities.dart';
 import '../elements/resolution_types.dart';
 import '../js/js.dart' as js;
 import '../js_backend/js_backend.dart';
 import '../js_backend/interceptor_data.dart' show InterceptorData;
 import '../js_backend/native_data.dart' show NativeData;
 import '../native/native.dart' as native;
 import '../options.dart';
-import '../tree/dartstring.dart' as ast;
 import '../types/types.dart';
 import '../universe/selector.dart' show Selector;
 import '../universe/side_effects.dart' show SideEffects;
 import '../util/util.dart';
 import '../world.dart' show ClosedWorld;
 import 'interceptor_simplifier.dart';
 import 'nodes.dart';
 import 'types.dart';
 import 'types_propagation.dart';
 import 'value_range_analyzer.dart';
@@ skipping 1095 matching lines @@
       leftString = getString(leftConcat.right);
       if (leftString == null) return node;
     }
 
     if (leftString.primitiveValue.length + rightString.primitiveValue.length >
         MAX_SHARED_CONSTANT_FOLDED_STRING_LENGTH) {
       if (node.usedBy.length > 1) return node;
     }
 
     HInstruction folded = _graph.addConstant(
-        constantSystem.createString(new ast.DartString.concat(
-            leftString.primitiveValue, rightString.primitiveValue)),
+        constantSystem.createString(
+            leftString.primitiveValue + rightString.primitiveValue),
         _closedWorld);
     if (prefix == null) return folded;
     return new HStringConcat(
         prefix, folded, _closedWorld.commonMasks.stringType);
   }
 
   HInstruction visitStringify(HStringify node) {
     HInstruction input = node.inputs[0];
     if (input.isString(_closedWorld)) return input;
 
     HInstruction tryConstant() {
       if (!input.isConstant()) return null;
       HConstant constant = input;
       if (!constant.constant.isPrimitive) return null;
       if (constant.constant.isInt) {
         // Only constant-fold int.toString() when Dart and JS results the same.
         // TODO(18103): We should be able to remove this work-around when issue
         // 18103 is resolved by providing the correct string.
         IntConstantValue intConstant = constant.constant;
         // Very conservative range.
         if (!intConstant.isUInt32()) return null;
       }
       PrimitiveConstantValue primitive = constant.constant;
       return _graph.addConstant(
-          constantSystem.createString(primitive.toDartString()), _closedWorld);
+          constantSystem.createString('${primitive.primitiveValue}'),
+          _closedWorld);
     }
 
     HInstruction tryToString() {
       // If the `toString` method is guaranteed to return a string we can call
       // it directly. Keep the stringifier for primitives (since they have fast
       // path code in the stringifier) and for classes requiring interceptors
       // (since SsaInstructionSimplifier runs after SsaSimplifyInterceptors).
       if (input.canBePrimitive(_closedWorld)) return null;
       if (input.canBeNull()) return null;
       Selector selector = Selectors.toString_;
@@ skipping 1818 matching lines @@
 
     keyedValues.forEach((receiver, values) {
       result.keyedValues[receiver] =
           new Map<HInstruction, HInstruction>.from(values);
     });
 
     result.nonEscapingReceivers.addAll(nonEscapingReceivers);
     return result;
   }
 }