Move constant implementation out of generated

pkg/analyzer/lib/src/generated/constant.dart

 // Copyright (c) 2014, 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 analyzer.src.generated.constant;
 
-import 'dart:collection';
-
+import 'package:analyzer/context/declared_variables.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/token.dart';
-import 'package:analyzer/dart/ast/visitor.dart';
-import 'package:analyzer/dart/constant/value.dart';
-import 'package:analyzer/dart/element/element.dart';
-import 'package:analyzer/dart/element/type.dart';
-import 'package:analyzer/src/dart/ast/utilities.dart';
-import 'package:analyzer/src/dart/element/element.dart';
-import 'package:analyzer/src/dart/element/handle.dart'
-    show ConstructorElementHandle;
-import 'package:analyzer/src/dart/element/member.dart';
+import 'package:analyzer/src/dart/constant/evaluation.dart';
+import 'package:analyzer/src/dart/constant/value.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/engine.dart'
     show AnalysisEngine, RecordingErrorListener;
 import 'package:analyzer/src/generated/error.dart';
-import 'package:analyzer/src/generated/java_core.dart';
 import 'package:analyzer/src/generated/resolver.dart' show TypeProvider;
 import 'package:analyzer/src/generated/source.dart' show Source;
 import 'package:analyzer/src/generated/type_system.dart'
     show TypeSystem, TypeSystemImpl;
-import 'package:analyzer/src/generated/utilities_collection.dart';
-import 'package:analyzer/src/generated/utilities_dart.dart' show ParameterKind;
-import 'package:analyzer/src/generated/utilities_general.dart';
-import 'package:analyzer/src/task/dart.dart';
 
+export 'package:analyzer/context/declared_variables.dart';
 export 'package:analyzer/dart/constant/value.dart';
-
-ConstructorElementImpl _getConstructorImpl(ConstructorElement constructor) {
-  while (constructor is ConstructorMember) {
-    constructor = (constructor as ConstructorMember).baseElement;
-  }
-  if (constructor is ConstructorElementHandle) {
-    constructor = (constructor as ConstructorElementHandle).actualElement;
-  }
-  return constructor;
-}
-
-/**
- * Callback used by [ReferenceFinder] to report that a dependency was found.
- */
-typedef void ReferenceFinderCallback(ConstantEvaluationTarget dependency);
-
-/**
- * The state of an object representing a boolean value.
- */
-class BoolState extends InstanceState {
-  /**
-   * An instance representing the boolean value 'false'.
-   */
-  static BoolState FALSE_STATE = new BoolState(false);
-
-  /**
-   * An instance representing the boolean value 'true'.
-   */
-  static BoolState TRUE_STATE = new BoolState(true);
-
-  /**
-   * A state that can be used to represent a boolean whose value is not known.
-   */
-  static BoolState UNKNOWN_VALUE = new BoolState(null);
-
-  /**
-   * The value of this instance.
-   */
-  final bool value;
-
-  /**
-   * Initialize a newly created state to represent the given [value].
-   */
-  BoolState(this.value);
-
-  @override
-  int get hashCode => value == null ? 0 : (value ? 2 : 3);
-
-  @override
-  bool get isBool => true;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  bool get isUnknown => value == null;
-
-  @override
-  String get typeName => "bool";
-
-  @override
-  bool operator ==(Object object) =>
-      object is BoolState && identical(value, object.value);
-
-  @override
-  BoolState convertToBool() => this;
-
-  @override
-  StringState convertToString() {
-    if (value == null) {
-      return StringState.UNKNOWN_VALUE;
-    }
-    return new StringState(value ? "true" : "false");
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is BoolState) {
-      bool rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return BoolState.from(identical(value, rightValue));
-    } else if (rightOperand is DynamicState) {
-      return UNKNOWN_VALUE;
-    }
-    return FALSE_STATE;
-  }
-
-  @override
-  BoolState logicalAnd(InstanceState rightOperand) {
-    assertBool(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    return value ? rightOperand.convertToBool() : FALSE_STATE;
-  }
-
-  @override
-  BoolState logicalNot() {
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    return value ? FALSE_STATE : TRUE_STATE;
-  }
-
-  @override
-  BoolState logicalOr(InstanceState rightOperand) {
-    assertBool(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    return value ? TRUE_STATE : rightOperand.convertToBool();
-  }
-
-  @override
-  String toString() => value == null ? "-unknown-" : (value ? "true" : "false");
-
-  /**
-   * Return the boolean state representing the given boolean [value].
-   */
-  static BoolState from(bool value) =>
-      value ? BoolState.TRUE_STATE : BoolState.FALSE_STATE;
-}
-
-/**
- * An [AstCloner] that copies the necessary information from the AST to allow
- * constants to be evaluated.
- */
-class ConstantAstCloner extends AstCloner {
-  ConstantAstCloner() : super(true);
-
-  @override
-  ConstructorName visitConstructorName(ConstructorName node) {
-    ConstructorName name = super.visitConstructorName(node);
-    name.staticElement = node.staticElement;
-    return name;
-  }
-
-  @override
-  InstanceCreationExpression visitInstanceCreationExpression(
-      InstanceCreationExpression node) {
-    InstanceCreationExpression expression =
-        super.visitInstanceCreationExpression(node);
-    expression.staticElement = node.staticElement;
-    return expression;
-  }
-
-  @override
-  RedirectingConstructorInvocation visitRedirectingConstructorInvocation(
-      RedirectingConstructorInvocation node) {
-    RedirectingConstructorInvocation invocation =
-        super.visitRedirectingConstructorInvocation(node);
-    invocation.staticElement = node.staticElement;
-    return invocation;
-  }
-
-  @override
-  SimpleIdentifier visitSimpleIdentifier(SimpleIdentifier node) {
-    SimpleIdentifier identifier = super.visitSimpleIdentifier(node);
-    identifier.staticElement = node.staticElement;
-    return identifier;
-  }
-
-  @override
-  SuperConstructorInvocation visitSuperConstructorInvocation(
-      SuperConstructorInvocation node) {
-    SuperConstructorInvocation invocation =
-        super.visitSuperConstructorInvocation(node);
-    invocation.staticElement = node.staticElement;
-    return invocation;
-  }
-
-  @override
-  TypeName visitTypeName(TypeName node) {
-    TypeName typeName = super.visitTypeName(node);
-    typeName.type = node.type;
-    return typeName;
-  }
-}
-
-/**
- * Helper class encapsulating the methods for evaluating constants and
- * constant instance creation expressions.
- */
-class ConstantEvaluationEngine {
-  /**
-   * Parameter to "fromEnvironment" methods that denotes the default value.
-   */
-  static String _DEFAULT_VALUE_PARAM = "defaultValue";
-
-  /**
-   * Source of RegExp matching any public identifier.
-   * From sdk/lib/internal/symbol.dart.
-   */
-  static String _PUBLIC_IDENTIFIER_RE =
-      "(?!${ConstantValueComputer._RESERVED_WORD_RE}\\b(?!\\\$))[a-zA-Z\$][\\w\$]*";
-
-  /**
-   * RegExp that validates a non-empty non-private symbol.
-   * From sdk/lib/internal/symbol.dart.
-   */
-  static RegExp _PUBLIC_SYMBOL_PATTERN = new RegExp(
-      "^(?:${ConstantValueComputer._OPERATOR_RE}\$|$_PUBLIC_IDENTIFIER_RE(?:=?\$|[.](?!\$)))+?\$");
-
-  /**
-   * The type provider used to access the known types.
-   */
-  final TypeProvider typeProvider;
-
-  /**
-   * The type system.  This is used to guess the types of constants when their
-   * exact value is unknown.
-   */
-  final TypeSystem typeSystem;
-
-  /**
-   * The set of variables declared on the command line using '-D'.
-   */
-  final DeclaredVariables _declaredVariables;
-
-  /**
-   * Validator used to verify correct dependency analysis when running unit
-   * tests.
-   */
-  final ConstantEvaluationValidator validator;
-
-  /**
-   * Initialize a newly created [ConstantEvaluationEngine].  The [typeProvider]
-   * is used to access known types.  [_declaredVariables] is the set of
-   * variables declared on the command line using '-D'.  The [validator], if
-   * given, is used to verify correct dependency analysis when running unit
-   * tests.
-   */
-  ConstantEvaluationEngine(this.typeProvider, this._declaredVariables,
-      {ConstantEvaluationValidator validator, TypeSystem typeSystem})
-      : validator = validator != null
-            ? validator
-            : new ConstantEvaluationValidator_ForProduction(),
-        typeSystem = typeSystem != null ? typeSystem : new TypeSystemImpl();
-
-  /**
-   * Check that the arguments to a call to fromEnvironment() are correct. The
-   * [arguments] are the AST nodes of the arguments. The [argumentValues] are
-   * the values of the unnamed arguments. The [namedArgumentValues] are the
-   * values of the named arguments. The [expectedDefaultValueType] is the
-   * allowed type of the "defaultValue" parameter (if present). Note:
-   * "defaultValue" is always allowed to be null. Return `true` if the arguments
-   * are correct, `false` if there is an error.
-   */
-  bool checkFromEnvironmentArguments(
-      NodeList<Expression> arguments,
-      List<DartObjectImpl> argumentValues,
-      HashMap<String, DartObjectImpl> namedArgumentValues,
-      InterfaceType expectedDefaultValueType) {
-    int argumentCount = arguments.length;
-    if (argumentCount < 1 || argumentCount > 2) {
-      return false;
-    }
-    if (arguments[0] is NamedExpression) {
-      return false;
-    }
-    if (!identical(argumentValues[0].type, typeProvider.stringType)) {
-      return false;
-    }
-    if (argumentCount == 2) {
-      if (arguments[1] is! NamedExpression) {
-        return false;
-      }
-      if (!((arguments[1] as NamedExpression).name.label.name ==
-          _DEFAULT_VALUE_PARAM)) {
-        return false;
-      }
-      ParameterizedType defaultValueType =
-          namedArgumentValues[_DEFAULT_VALUE_PARAM].type;
-      if (!(identical(defaultValueType, expectedDefaultValueType) ||
-          identical(defaultValueType, typeProvider.nullType))) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  /**
-   * Check that the arguments to a call to Symbol() are correct. The [arguments]
-   * are the AST nodes of the arguments. The [argumentValues] are the values of
-   * the unnamed arguments. The [namedArgumentValues] are the values of the
-   * named arguments. Return `true` if the arguments are correct, `false` if
-   * there is an error.
-   */
-  bool checkSymbolArguments(
-      NodeList<Expression> arguments,
-      List<DartObjectImpl> argumentValues,
-      HashMap<String, DartObjectImpl> namedArgumentValues) {
-    if (arguments.length != 1) {
-      return false;
-    }
-    if (arguments[0] is NamedExpression) {
-      return false;
-    }
-    if (!identical(argumentValues[0].type, typeProvider.stringType)) {
-      return false;
-    }
-    String name = argumentValues[0].toStringValue();
-    return isValidPublicSymbol(name);
-  }
-
-  /**
-   * Compute the constant value associated with the given [constant].
-   */
-  void computeConstantValue(ConstantEvaluationTarget constant) {
-    validator.beforeComputeValue(constant);
-    if (constant is ParameterElementImpl) {
-      Expression defaultValue = constant.constantInitializer;
-      if (defaultValue != null) {
-        RecordingErrorListener errorListener = new RecordingErrorListener();
-        ErrorReporter errorReporter =
-            new ErrorReporter(errorListener, constant.source);
-        DartObjectImpl dartObject =
-            defaultValue.accept(new ConstantVisitor(this, errorReporter));
-        constant.evaluationResult =
-            new EvaluationResultImpl(dartObject, errorListener.errors);
-      }
-    } else if (constant is VariableElementImpl) {
-      Expression constantInitializer = constant.constantInitializer;
-      if (constantInitializer != null) {
-        RecordingErrorListener errorListener = new RecordingErrorListener();
-        ErrorReporter errorReporter =
-            new ErrorReporter(errorListener, constant.source);
-        DartObjectImpl dartObject = constantInitializer
-            .accept(new ConstantVisitor(this, errorReporter));
-        // Only check the type for truly const declarations (don't check final
-        // fields with initializers, since their types may be generic.  The type
-        // of the final field will be checked later, when the constructor is
-        // invoked).
-        if (dartObject != null && constant.isConst) {
-          if (!runtimeTypeMatch(dartObject, constant.type)) {
-            errorReporter.reportErrorForElement(
-                CheckedModeCompileTimeErrorCode.VARIABLE_TYPE_MISMATCH,
-                constant,
-                [dartObject.type, constant.type]);
-          }
-        }
-        constant.evaluationResult =
-            new EvaluationResultImpl(dartObject, errorListener.errors);
-      }
-    } else if (constant is ConstructorElement) {
-      if (constant.isConst) {
-        // No evaluation needs to be done; constructor declarations are only in
-        // the dependency graph to ensure that any constants referred to in
-        // initializer lists and parameter defaults are evaluated before
-        // invocations of the constructor.  However we do need to annotate the
-        // element as being free of constant evaluation cycles so that later
-        // code will know that it is safe to evaluate.
-        (constant as ConstructorElementImpl).isCycleFree = true;
-      }
-    } else if (constant is ElementAnnotationImpl) {
-      Annotation constNode = constant.annotationAst;
-      Element element = constant.element;
-      if (element is PropertyAccessorElement &&
-          element.variable is VariableElementImpl) {
-        // The annotation is a reference to a compile-time constant variable.
-        // Just copy the evaluation result.
-        VariableElementImpl variableElement =
-            element.variable as VariableElementImpl;
-        if (variableElement.evaluationResult != null) {
-          constant.evaluationResult = variableElement.evaluationResult;
-        } else {
-          // This could happen in the event that the annotation refers to a
-          // non-constant.  The error is detected elsewhere, so just silently
-          // ignore it here.
-          constant.evaluationResult = new EvaluationResultImpl(null);
-        }
-      } else if (element is ConstructorElementImpl &&
-          element.isConst &&
-          constNode.arguments != null) {
-        RecordingErrorListener errorListener = new RecordingErrorListener();
-        ErrorReporter errorReporter =
-            new ErrorReporter(errorListener, constant.source);
-        ConstantVisitor constantVisitor =
-            new ConstantVisitor(this, errorReporter);
-        DartObjectImpl result = evaluateConstructorCall(
-            constNode,
-            constNode.arguments.arguments,
-            element,
-            constantVisitor,
-            errorReporter);
-        constant.evaluationResult =
-            new EvaluationResultImpl(result, errorListener.errors);
-      } else {
-        // This may happen for invalid code (e.g. failing to pass arguments
-        // to an annotation which references a const constructor).  The error
-        // is detected elsewhere, so just silently ignore it here.
-        constant.evaluationResult = new EvaluationResultImpl(null);
-      }
-    } else if (constant is VariableElement) {
-      // constant is a VariableElement but not a VariableElementImpl.  This can
-      // happen sometimes in the case of invalid user code (for example, a
-      // constant expression that refers to a non-static field inside a generic
-      // class will wind up referring to a FieldMember).  The error is detected
-      // elsewhere, so just silently ignore it here.
-    } else {
-      // Should not happen.
-      assert(false);
-      AnalysisEngine.instance.logger.logError(
-          "Constant value computer trying to compute the value of a node of type ${constant.runtimeType}");
-      return;
-    }
-  }
-
-  /**
-   * Determine which constant elements need to have their values computed
-   * prior to computing the value of [constant], and report them using
-   * [callback].
-   */
-  void computeDependencies(
-      ConstantEvaluationTarget constant, ReferenceFinderCallback callback) {
-    ReferenceFinder referenceFinder = new ReferenceFinder(callback);
-    if (constant is ConstructorElement) {
-      constant = _getConstructorImpl(constant);
-    }
-    if (constant is VariableElementImpl) {
-      Expression initializer = constant.constantInitializer;
-      if (initializer != null) {
-        initializer.accept(referenceFinder);
-      }
-    } else if (constant is ConstructorElementImpl) {
-      if (constant.isConst) {
-        constant.isCycleFree = false;
-        ConstructorElement redirectedConstructor =
-            getConstRedirectedConstructor(constant);
-        if (redirectedConstructor != null) {
-          ConstructorElement redirectedConstructorBase =
-              _getConstructorImpl(redirectedConstructor);
-          callback(redirectedConstructorBase);
-          return;
-        } else if (constant.isFactory) {
-          // Factory constructor, but getConstRedirectedConstructor returned
-          // null.  This can happen if we're visiting one of the special external
-          // const factory constructors in the SDK, or if the code contains
-          // errors (such as delegating to a non-const constructor, or delegating
-          // to a constructor that can't be resolved).  In any of these cases,
-          // we'll evaluate calls to this constructor without having to refer to
-          // any other constants.  So we don't need to report any dependencies.
-          return;
-        }
-        bool superInvocationFound = false;
-        List<ConstructorInitializer> initializers =
-            constant.constantInitializers;
-        for (ConstructorInitializer initializer in initializers) {
-          if (initializer is SuperConstructorInvocation) {
-            superInvocationFound = true;
-          }
-          initializer.accept(referenceFinder);
-        }
-        if (!superInvocationFound) {
-          // No explicit superconstructor invocation found, so we need to
-          // manually insert a reference to the implicit superconstructor.
-          InterfaceType superclass =
-              (constant.returnType as InterfaceType).superclass;
-          if (superclass != null && !superclass.isObject) {
-            ConstructorElement unnamedConstructor =
-                _getConstructorImpl(superclass.element.unnamedConstructor);
-            if (unnamedConstructor != null) {
-              callback(unnamedConstructor);
-            }
-          }
-        }
-        for (FieldElement field in constant.enclosingElement.fields) {
-          // Note: non-static const isn't allowed but we handle it anyway so
-          // that we won't be confused by incorrect code.
-          if ((field.isFinal || field.isConst) &&
-              !field.isStatic &&
-              field.initializer != null) {
-            callback(field);
-          }
-        }
-        for (ParameterElement parameterElement in constant.parameters) {
-          callback(parameterElement);
-        }
-      }
-    } else if (constant is ElementAnnotationImpl) {
-      Annotation constNode = constant.annotationAst;
-      Element element = constant.element;
-      if (element is PropertyAccessorElement &&
-          element.variable is VariableElementImpl) {
-        // The annotation is a reference to a compile-time constant variable,
-        // so it depends on the variable.
-        callback(element.variable);
-      } else if (element is ConstructorElementImpl) {
-        // The annotation is a constructor invocation, so it depends on the
-        // constructor.
-        callback(element);
-      } else {
-        // This could happen in the event of invalid code.  The error will be
-        // reported at constant evaluation time.
-      }
-      if (constNode.arguments != null) {
-        constNode.arguments.accept(referenceFinder);
-      }
-    } else if (constant is VariableElement) {
-      // constant is a VariableElement but not a VariableElementImpl.  This can
-      // happen sometimes in the case of invalid user code (for example, a
-      // constant expression that refers to a non-static field inside a generic
-      // class will wind up referring to a FieldMember).  So just don't bother
-      // computing any dependencies.
-    } else {
-      // Should not happen.
-      assert(false);
-      AnalysisEngine.instance.logger.logError(
-          "Constant value computer trying to compute the value of a node of type ${constant.runtimeType}");
-    }
-  }
-
-  /**
-   * Evaluate a call to fromEnvironment() on the bool, int, or String class. The
-   * [environmentValue] is the value fetched from the environment. The
-   * [builtInDefaultValue] is the value that should be used as the default if no
-   * "defaultValue" argument appears in [namedArgumentValues]. The
-   * [namedArgumentValues] are the values of the named parameters passed to
-   * fromEnvironment(). Return a [DartObjectImpl] object corresponding to the
-   * evaluated result.
-   */
-  DartObjectImpl computeValueFromEnvironment(
-      DartObject environmentValue,
-      DartObjectImpl builtInDefaultValue,
-      HashMap<String, DartObjectImpl> namedArgumentValues) {
-    DartObjectImpl value = environmentValue as DartObjectImpl;
-    if (value.isUnknown || value.isNull) {
-      // The name either doesn't exist in the environment or we couldn't parse
-      // the corresponding value.
-      // If the code supplied an explicit default, use it.
-      if (namedArgumentValues.containsKey(_DEFAULT_VALUE_PARAM)) {
-        value = namedArgumentValues[_DEFAULT_VALUE_PARAM];
-      } else if (value.isNull) {
-        // The code didn't supply an explicit default.
-        // The name exists in the environment but we couldn't parse the
-        // corresponding value.
-        // So use the built-in default value, because this is what the VM does.
-        value = builtInDefaultValue;
-      } else {
-        // The code didn't supply an explicit default.
-        // The name doesn't exist in the environment.
-        // The VM would use the built-in default value, but we don't want to do
-        // that for analysis because it's likely to lead to cascading errors.
-        // So just leave [value] in the unknown state.
-      }
-    }
-    return value;
-  }
-
-  DartObjectImpl evaluateConstructorCall(
-      AstNode node,
-      NodeList<Expression> arguments,
-      ConstructorElement constructor,
-      ConstantVisitor constantVisitor,
-      ErrorReporter errorReporter) {
-    if (!_getConstructorImpl(constructor).isCycleFree) {
-      // It's not safe to evaluate this constructor, so bail out.
-      // TODO(paulberry): ensure that a reasonable error message is produced
-      // in this case, as well as other cases involving constant expression
-      // circularities (e.g. "compile-time constant expression depends on
-      // itself")
-      return new DartObjectImpl.validWithUnknownValue(constructor.returnType);
-    }
-    int argumentCount = arguments.length;
-    List<DartObjectImpl> argumentValues =
-        new List<DartObjectImpl>(argumentCount);
-    List<Expression> argumentNodes = new List<Expression>(argumentCount);
-    HashMap<String, DartObjectImpl> namedArgumentValues =
-        new HashMap<String, DartObjectImpl>();
-    HashMap<String, NamedExpression> namedArgumentNodes =
-        new HashMap<String, NamedExpression>();
-    for (int i = 0; i < argumentCount; i++) {
-      Expression argument = arguments[i];
-      if (argument is NamedExpression) {
-        String name = argument.name.label.name;
-        namedArgumentValues[name] =
-            constantVisitor._valueOf(argument.expression);
-        namedArgumentNodes[name] = argument;
-        argumentValues[i] = typeProvider.nullObject;
-      } else {
-        argumentValues[i] = constantVisitor._valueOf(argument);
-        argumentNodes[i] = argument;
-      }
-    }
-    constructor = followConstantRedirectionChain(constructor);
-    InterfaceType definingClass = constructor.returnType as InterfaceType;
-    if (constructor.isFactory) {
-      // We couldn't find a non-factory constructor.
-      // See if it's because we reached an external const factory constructor
-      // that we can emulate.
-      if (constructor.name == "fromEnvironment") {
-        if (!checkFromEnvironmentArguments(
-            arguments, argumentValues, namedArgumentValues, definingClass)) {
-          errorReporter.reportErrorForNode(
-              CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
-          return null;
-        }
-        String variableName =
-            argumentCount < 1 ? null : argumentValues[0].toStringValue();
-        if (identical(definingClass, typeProvider.boolType)) {
-          DartObject valueFromEnvironment;
-          valueFromEnvironment =
-              _declaredVariables.getBool(typeProvider, variableName);
-          return computeValueFromEnvironment(
-              valueFromEnvironment,
-              new DartObjectImpl(typeProvider.boolType, BoolState.FALSE_STATE),
-              namedArgumentValues);
-        } else if (identical(definingClass, typeProvider.intType)) {
-          DartObject valueFromEnvironment;
-          valueFromEnvironment =
-              _declaredVariables.getInt(typeProvider, variableName);
-          return computeValueFromEnvironment(
-              valueFromEnvironment,
-              new DartObjectImpl(typeProvider.nullType, NullState.NULL_STATE),
-              namedArgumentValues);
-        } else if (identical(definingClass, typeProvider.stringType)) {
-          DartObject valueFromEnvironment;
-          valueFromEnvironment =
-              _declaredVariables.getString(typeProvider, variableName);
-          return computeValueFromEnvironment(
-              valueFromEnvironment,
-              new DartObjectImpl(typeProvider.nullType, NullState.NULL_STATE),
-              namedArgumentValues);
-        }
-      } else if (constructor.name == "" &&
-          identical(definingClass, typeProvider.symbolType) &&
-          argumentCount == 1) {
-        if (!checkSymbolArguments(
-            arguments, argumentValues, namedArgumentValues)) {
-          errorReporter.reportErrorForNode(
-              CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
-          return null;
-        }
-        String argumentValue = argumentValues[0].toStringValue();
-        return new DartObjectImpl(
-            definingClass, new SymbolState(argumentValue));
-      }
-      // Either it's an external const factory constructor that we can't
-      // emulate, or an error occurred (a cycle, or a const constructor trying
-      // to delegate to a non-const constructor).
-      // In the former case, the best we can do is consider it an unknown value.
-      // In the latter case, the error has already been reported, so considering
-      // it an unknown value will suppress further errors.
-      return new DartObjectImpl.validWithUnknownValue(definingClass);
-    }
-    ConstructorElementImpl constructorBase = _getConstructorImpl(constructor);
-    validator.beforeGetConstantInitializers(constructorBase);
-    List<ConstructorInitializer> initializers =
-        constructorBase.constantInitializers;
-    if (initializers == null) {
-      // This can happen in some cases where there are compile errors in the
-      // code being analyzed (for example if the code is trying to create a
-      // const instance using a non-const constructor, or the node we're
-      // visiting is involved in a cycle).  The error has already been reported,
-      // so consider it an unknown value to suppress further errors.
-      return new DartObjectImpl.validWithUnknownValue(definingClass);
-    }
-    HashMap<String, DartObjectImpl> fieldMap =
-        new HashMap<String, DartObjectImpl>();
-    // Start with final fields that are initialized at their declaration site.
-    for (FieldElement field in constructor.enclosingElement.fields) {
-      if ((field.isFinal || field.isConst) &&
-          !field.isStatic &&
-          field is ConstFieldElementImpl) {
-        validator.beforeGetFieldEvaluationResult(field);
-        EvaluationResultImpl evaluationResult = field.evaluationResult;
-        // It is possible that the evaluation result is null.
-        // This happens for example when we have duplicate fields.
-        // class Test {final x = 1; final x = 2; const Test();}
-        if (evaluationResult == null) {
-          continue;
-        }
-        // Match the value and the type.
-        DartType fieldType =
-            FieldMember.from(field, constructor.returnType).type;
-        DartObjectImpl fieldValue = evaluationResult.value;
-        if (fieldValue != null && !runtimeTypeMatch(fieldValue, fieldType)) {
-          errorReporter.reportErrorForNode(
-              CheckedModeCompileTimeErrorCode
-                  .CONST_CONSTRUCTOR_FIELD_TYPE_MISMATCH,
-              node,
-              [fieldValue.type, field.name, fieldType]);
-        }
-        fieldMap[field.name] = fieldValue;
-      }
-    }
-    // Now evaluate the constructor declaration.
-    HashMap<String, DartObjectImpl> parameterMap =
-        new HashMap<String, DartObjectImpl>();
-    List<ParameterElement> parameters = constructor.parameters;
-    int parameterCount = parameters.length;
-    for (int i = 0; i < parameterCount; i++) {
-      ParameterElement parameter = parameters[i];
-      ParameterElement baseParameter = parameter;
-      while (baseParameter is ParameterMember) {
-        baseParameter = (baseParameter as ParameterMember).baseElement;
-      }
-      DartObjectImpl argumentValue = null;
-      AstNode errorTarget = null;
-      if (baseParameter.parameterKind == ParameterKind.NAMED) {
-        argumentValue = namedArgumentValues[baseParameter.name];
-        errorTarget = namedArgumentNodes[baseParameter.name];
-      } else if (i < argumentCount) {
-        argumentValue = argumentValues[i];
-        errorTarget = argumentNodes[i];
-      }
-      if (errorTarget == null) {
-        // No argument node that we can direct error messages to, because we
-        // are handling an optional parameter that wasn't specified.  So just
-        // direct error messages to the constructor call.
-        errorTarget = node;
-      }
-      if (argumentValue == null && baseParameter is ParameterElementImpl) {
-        // The parameter is an optional positional parameter for which no value
-        // was provided, so use the default value.
-        validator.beforeGetParameterDefault(baseParameter);
-        EvaluationResultImpl evaluationResult = baseParameter.evaluationResult;
-        if (evaluationResult == null) {
-          // No default was provided, so the default value is null.
-          argumentValue = typeProvider.nullObject;
-        } else if (evaluationResult.value != null) {
-          argumentValue = evaluationResult.value;
-        }
-      }
-      if (argumentValue != null) {
-        if (!runtimeTypeMatch(argumentValue, parameter.type)) {
-          errorReporter.reportErrorForNode(
-              CheckedModeCompileTimeErrorCode
-                  .CONST_CONSTRUCTOR_PARAM_TYPE_MISMATCH,
-              errorTarget,
-              [argumentValue.type, parameter.type]);
-        }
-        if (baseParameter.isInitializingFormal) {
-          FieldElement field = (parameter as FieldFormalParameterElement).field;
-          if (field != null) {
-            DartType fieldType = field.type;
-            if (fieldType != parameter.type) {
-              // We've already checked that the argument can be assigned to the
-              // parameter; we also need to check that it can be assigned to
-              // the field.
-              if (!runtimeTypeMatch(argumentValue, fieldType)) {
-                errorReporter.reportErrorForNode(
-                    CheckedModeCompileTimeErrorCode
-                        .CONST_CONSTRUCTOR_PARAM_TYPE_MISMATCH,
-                    errorTarget,
-                    [argumentValue.type, fieldType]);
-              }
-            }
-            String fieldName = field.name;
-            if (fieldMap.containsKey(fieldName)) {
-              errorReporter.reportErrorForNode(
-                  CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
-            }
-            fieldMap[fieldName] = argumentValue;
-          }
-        } else {
-          String name = baseParameter.name;
-          parameterMap[name] = argumentValue;
-        }
-      }
-    }
-    ConstantVisitor initializerVisitor = new ConstantVisitor(
-        this, errorReporter,
-        lexicalEnvironment: parameterMap);
-    String superName = null;
-    NodeList<Expression> superArguments = null;
-    for (ConstructorInitializer initializer in initializers) {
-      if (initializer is ConstructorFieldInitializer) {
-        ConstructorFieldInitializer constructorFieldInitializer = initializer;
-        Expression initializerExpression =
-            constructorFieldInitializer.expression;
-        DartObjectImpl evaluationResult =
-            initializerExpression.accept(initializerVisitor);
-        if (evaluationResult != null) {
-          String fieldName = constructorFieldInitializer.fieldName.name;
-          if (fieldMap.containsKey(fieldName)) {
-            errorReporter.reportErrorForNode(
-                CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION, node);
-          }
-          fieldMap[fieldName] = evaluationResult;
-          PropertyAccessorElement getter = definingClass.getGetter(fieldName);
-          if (getter != null) {
-            PropertyInducingElement field = getter.variable;
-            if (!runtimeTypeMatch(evaluationResult, field.type)) {
-              errorReporter.reportErrorForNode(
-                  CheckedModeCompileTimeErrorCode
-                      .CONST_CONSTRUCTOR_FIELD_TYPE_MISMATCH,
-                  node,
-                  [evaluationResult.type, fieldName, field.type]);
-            }
-          }
-        }
-      } else if (initializer is SuperConstructorInvocation) {
-        SuperConstructorInvocation superConstructorInvocation = initializer;
-        SimpleIdentifier name = superConstructorInvocation.constructorName;
-        if (name != null) {
-          superName = name.name;
-        }
-        superArguments = superConstructorInvocation.argumentList.arguments;
-      } else if (initializer is RedirectingConstructorInvocation) {
-        // This is a redirecting constructor, so just evaluate the constructor
-        // it redirects to.
-        ConstructorElement constructor = initializer.staticElement;
-        if (constructor != null && constructor.isConst) {
-          return evaluateConstructorCall(
-              node,
-              initializer.argumentList.arguments,
-              constructor,
-              initializerVisitor,
-              errorReporter);
-        }
-      }
-    }
-    // Evaluate explicit or implicit call to super().
-    InterfaceType superclass = definingClass.superclass;
-    if (superclass != null && !superclass.isObject) {
-      ConstructorElement superConstructor =
-          superclass.lookUpConstructor(superName, constructor.library);
-      if (superConstructor != null) {
-        if (superArguments == null) {
-          superArguments = new NodeList<Expression>(null);
-        }
-        evaluateSuperConstructorCall(node, fieldMap, superConstructor,
-            superArguments, initializerVisitor, errorReporter);
-      }
-    }
-    return new DartObjectImpl(definingClass, new GenericState(fieldMap));
-  }
-
-  void evaluateSuperConstructorCall(
-      AstNode node,
-      HashMap<String, DartObjectImpl> fieldMap,
-      ConstructorElement superConstructor,
-      NodeList<Expression> superArguments,
-      ConstantVisitor initializerVisitor,
-      ErrorReporter errorReporter) {
-    if (superConstructor != null && superConstructor.isConst) {
-      DartObjectImpl evaluationResult = evaluateConstructorCall(node,
-          superArguments, superConstructor, initializerVisitor, errorReporter);
-      if (evaluationResult != null) {
-        fieldMap[GenericState.SUPERCLASS_FIELD] = evaluationResult;
-      }
-    }
-  }
-
-  /**
-   * Attempt to follow the chain of factory redirections until a constructor is
-   * reached which is not a const factory constructor. Return the constant
-   * constructor which terminates the chain of factory redirections, if the
-   * chain terminates. If there is a problem (e.g. a redirection can't be found,
-   * or a cycle is encountered), the chain will be followed as far as possible
-   * and then a const factory constructor will be returned.
-   */
-  ConstructorElement followConstantRedirectionChain(
-      ConstructorElement constructor) {
-    HashSet<ConstructorElement> constructorsVisited =
-        new HashSet<ConstructorElement>();
-    while (true) {
-      ConstructorElement redirectedConstructor =
-          getConstRedirectedConstructor(constructor);
-      if (redirectedConstructor == null) {
-        break;
-      } else {
-        ConstructorElement constructorBase = _getConstructorImpl(constructor);
-        constructorsVisited.add(constructorBase);
-        ConstructorElement redirectedConstructorBase =
-            _getConstructorImpl(redirectedConstructor);
-        if (constructorsVisited.contains(redirectedConstructorBase)) {
-          // Cycle in redirecting factory constructors--this is not allowed
-          // and is checked elsewhere--see
-          // [ErrorVerifier.checkForRecursiveFactoryRedirect()]).
-          break;
-        }
-      }
-      constructor = redirectedConstructor;
-    }
-    return constructor;
-  }
-
-  /**
-   * Generate an error indicating that the given [constant] is not a valid
-   * compile-time constant because it references at least one of the constants
-   * in the given [cycle], each of which directly or indirectly references the
-   * constant.
-   */
-  void generateCycleError(Iterable<ConstantEvaluationTarget> cycle,
-      ConstantEvaluationTarget constant) {
-    if (constant is VariableElement) {
-      RecordingErrorListener errorListener = new RecordingErrorListener();
-      ErrorReporter errorReporter =
-          new ErrorReporter(errorListener, constant.source);
-      // TODO(paulberry): It would be really nice if we could extract enough
-      // information from the 'cycle' argument to provide the user with a
-      // description of the cycle.
-      errorReporter.reportErrorForElement(
-          CompileTimeErrorCode.RECURSIVE_COMPILE_TIME_CONSTANT, constant, []);
-      (constant as VariableElementImpl).evaluationResult =
-          new EvaluationResultImpl(null, errorListener.errors);
-    } else if (constant is ConstructorElement) {
-      // We don't report cycle errors on constructor declarations since there
-      // is nowhere to put the error information.
-    } else {
-      // Should not happen.  Formal parameter defaults and annotations should
-      // never appear as part of a cycle because they can't be referred to.
-      assert(false);
-      AnalysisEngine.instance.logger.logError(
-          "Constant value computer trying to report a cycle error for a node of type ${constant.runtimeType}");
-    }
-  }
-
-  /**
-   * If [constructor] redirects to another const constructor, return the
-   * const constructor it redirects to.  Otherwise return `null`.
-   */
-  ConstructorElement getConstRedirectedConstructor(
-      ConstructorElement constructor) {
-    if (!constructor.isFactory) {
-      return null;
-    }
-    if (identical(constructor.enclosingElement.type, typeProvider.symbolType)) {
-      // The dart:core.Symbol has a const factory constructor that redirects
-      // to dart:_internal.Symbol.  That in turn redirects to an external
-      // const constructor, which we won't be able to evaluate.
-      // So stop following the chain of redirections at dart:core.Symbol, and
-      // let [evaluateInstanceCreationExpression] handle it specially.
-      return null;
-    }
-    ConstructorElement redirectedConstructor =
-        constructor.redirectedConstructor;
-    if (redirectedConstructor == null) {
-      // This can happen if constructor is an external factory constructor.
-      return null;
-    }
-    if (!redirectedConstructor.isConst) {
-      // Delegating to a non-const constructor--this is not allowed (and
-      // is checked elsewhere--see
-      // [ErrorVerifier.checkForRedirectToNonConstConstructor()]).
-      return null;
-    }
-    return redirectedConstructor;
-  }
-
-  /**
-   * Check if the object [obj] matches the type [type] according to runtime type
-   * checking rules.
-   */
-  bool runtimeTypeMatch(DartObjectImpl obj, DartType type) {
-    if (obj.isNull) {
-      return true;
-    }
-    if (type.isUndefined) {
-      return false;
-    }
-    return obj.type.isSubtypeOf(type);
-  }
-
-  /**
-   * Determine whether the given string is a valid name for a public symbol
-   * (i.e. whether it is allowed for a call to the Symbol constructor).
-   */
-  static bool isValidPublicSymbol(String name) =>
-      name.isEmpty ||
-      name == "void" ||
-      new JavaPatternMatcher(_PUBLIC_SYMBOL_PATTERN, name).matches();
-}
-
-/**
- * Interface used by unit tests to verify correct dependency analysis during
- * constant evaluation.
- */
-abstract class ConstantEvaluationValidator {
-  /**
-   * This method is called just before computing the constant value associated
-   * with [constant]. Unit tests will override this method to introduce
-   * additional error checking.
-   */
-  void beforeComputeValue(ConstantEvaluationTarget constant);
-
-  /**
-   * This method is called just before getting the constant initializers
-   * associated with the [constructor]. Unit tests will override this method to
-   * introduce additional error checking.
-   */
-  void beforeGetConstantInitializers(ConstructorElement constructor);
-
-  /**
-   * This method is called just before retrieving an evaluation result from an
-   * element. Unit tests will override it to introduce additional error
-   * checking.
-   */
-  void beforeGetEvaluationResult(ConstantEvaluationTarget constant);
-
-  /**
-   * This method is called just before getting the constant value of a field
-   * with an initializer.  Unit tests will override this method to introduce
-   * additional error checking.
-   */
-  void beforeGetFieldEvaluationResult(FieldElementImpl field);
-
-  /**
-   * This method is called just before getting a parameter's default value. Unit
-   * tests will override this method to introduce additional error checking.
-   */
-  void beforeGetParameterDefault(ParameterElement parameter);
-}
-
-/**
- * Implementation of [ConstantEvaluationValidator] used in production; does no
- * validation.
- */
-class ConstantEvaluationValidator_ForProduction
-    implements ConstantEvaluationValidator {
-  @override
-  void beforeComputeValue(ConstantEvaluationTarget constant) {}
-
-  @override
-  void beforeGetConstantInitializers(ConstructorElement constructor) {}
-
-  @override
-  void beforeGetEvaluationResult(ConstantEvaluationTarget constant) {}
-
-  @override
-  void beforeGetFieldEvaluationResult(FieldElementImpl field) {}
-
-  @override
-  void beforeGetParameterDefault(ParameterElement parameter) {}
-}
+export 'package:analyzer/src/dart/constant/evaluation.dart';
+export 'package:analyzer/src/dart/constant/utilities.dart';
+export 'package:analyzer/src/dart/constant/value.dart';
 
 /// Instances of the class [ConstantEvaluator] evaluate constant expressions to
 /// produce their compile-time value.
 ///
 /// According to the Dart Language Specification:
 ///
 /// > A constant expression is one of the following:
 /// >
 /// > * A literal number.
 /// > * A literal boolean.
@@ skipping 56 matching lines @@
 /// >   evaluates to a boolean value.
 /// >   </span>
 ///
 /// The values returned by instances of this class are therefore `null` and
 /// instances of the classes `Boolean`, `BigInteger`, `Double`, `String`, and
 /// `DartObject`.
 ///
 /// In addition, this class defines several values that can be returned to
 /// indicate various conditions encountered during evaluation. These are
 /// documented with the static fields that define those values.
+@deprecated
 class ConstantEvaluator {
   /**
    * The source containing the expression(s) that will be evaluated.
    */
   final Source _source;
 
   /**
    * The type provider used to access the known types.
    */
   final TypeProvider _typeProvider;
@@ skipping 17 matching lines @@
     DartObjectImpl result = expression.accept(new ConstantVisitor(
         new ConstantEvaluationEngine(_typeProvider, new DeclaredVariables(),
             typeSystem: _typeSystem),
         errorReporter));
     if (result != null) {
       return EvaluationResult.forValue(result);
     }
     return EvaluationResult.forErrors(errorListener.errors);
   }
 }
-
-/**
- * A visitor used to traverse the AST structures of all of the compilation units
- * being resolved and build the full set of dependencies for all constant
- * expressions.
- */
-class ConstantExpressionsDependenciesFinder extends RecursiveAstVisitor {
-  /**
-   * The constants whose values need to be computed.
-   */
-  HashSet<ConstantEvaluationTarget> dependencies =
-      new HashSet<ConstantEvaluationTarget>();
-
-  @override
-  void visitInstanceCreationExpression(InstanceCreationExpression node) {
-    if (node.isConst) {
-      _find(node);
-    } else {
-      super.visitInstanceCreationExpression(node);
-    }
-  }
-
-  @override
-  void visitListLiteral(ListLiteral node) {
-    if (node.constKeyword != null) {
-      _find(node);
-    } else {
-      super.visitListLiteral(node);
-    }
-  }
-
-  @override
-  void visitMapLiteral(MapLiteral node) {
-    if (node.constKeyword != null) {
-      _find(node);
-    } else {
-      super.visitMapLiteral(node);
-    }
-  }
-
-  @override
-  void visitSwitchCase(SwitchCase node) {
-    _find(node.expression);
-    node.statements.accept(this);
-  }
-
-  void _find(Expression node) {
-    if (node != null) {
-      ReferenceFinder referenceFinder = new ReferenceFinder(dependencies.add);
-      node.accept(referenceFinder);
-    }
-  }
-}
-
-/**
- * A visitor used to traverse the AST structures of all of the compilation units
- * being resolved and build tables of the constant variables, constant
- * constructors, constant constructor invocations, and annotations found in
- * those compilation units.
- */
-class ConstantFinder extends RecursiveAstVisitor<Object> {
-  final AnalysisContext context;
-  final Source source;
-  final Source librarySource;
-
-  /**
-   * The elements and AST nodes whose constant values need to be computed.
-   */
-  List<ConstantEvaluationTarget> constantsToCompute =
-      <ConstantEvaluationTarget>[];
-
-  /**
-   * True if instance variables marked as "final" should be treated as "const".
-   */
-  bool treatFinalInstanceVarAsConst = false;
-
-  ConstantFinder(this.context, this.source, this.librarySource);
-
-  @override
-  Object visitAnnotation(Annotation node) {
-    super.visitAnnotation(node);
-    ElementAnnotation elementAnnotation = node.elementAnnotation;
-    if (elementAnnotation == null) {
-      // Analyzer ignores annotations on "part of" directives.
-      assert(node.parent is PartOfDirective);
-    } else {
-      constantsToCompute.add(elementAnnotation);
-    }
-    return null;
-  }
-
-  @override
-  Object visitClassDeclaration(ClassDeclaration node) {
-    bool prevTreatFinalInstanceVarAsConst = treatFinalInstanceVarAsConst;
-    if (node.element.constructors.any((ConstructorElement e) => e.isConst)) {
-      // Instance vars marked "final" need to be included in the dependency
-      // graph, since constant constructors implicitly use the values in their
-      // initializers.
-      treatFinalInstanceVarAsConst = true;
-    }
-    try {
-      return super.visitClassDeclaration(node);
-    } finally {
-      treatFinalInstanceVarAsConst = prevTreatFinalInstanceVarAsConst;
-    }
-  }
-
-  @override
-  Object visitConstructorDeclaration(ConstructorDeclaration node) {
-    super.visitConstructorDeclaration(node);
-    if (node.constKeyword != null) {
-      ConstructorElement element = node.element;
-      if (element != null) {
-        constantsToCompute.add(element);
-        constantsToCompute.addAll(element.parameters);
-      }
-    }
-    return null;
-  }
-
-  @override
-  Object visitDefaultFormalParameter(DefaultFormalParameter node) {
-    super.visitDefaultFormalParameter(node);
-    Expression defaultValue = node.defaultValue;
-    if (defaultValue != null && node.element != null) {
-      constantsToCompute.add(node.element);
-    }
-    return null;
-  }
-
-  @override
-  Object visitVariableDeclaration(VariableDeclaration node) {
-    super.visitVariableDeclaration(node);
-    Expression initializer = node.initializer;
-    VariableElement element = node.element;
-    if (initializer != null &&
-        (node.isConst ||
-            treatFinalInstanceVarAsConst &&
-                element is FieldElement &&
-                node.isFinal &&
-                !element.isStatic)) {
-      if (element != null) {
-        constantsToCompute.add(element);
-      }
-    }
-    return null;
-  }
-}
-
-/**
- * An object used to compute the values of constant variables and constant
- * constructor invocations in one or more compilation units. The expected usage
- * pattern is for the compilation units to be added to this computer using the
- * method [add] and then for the method [computeValues] to be invoked exactly
- * once. Any use of an instance after invoking the method [computeValues] will
- * result in unpredictable behavior.
- */
-class ConstantValueComputer {
-  /**
-   * Source of RegExp matching declarable operator names.
-   * From sdk/lib/internal/symbol.dart.
-   */
-  static String _OPERATOR_RE =
-      "(?:[\\-+*/%&|^]|\\[\\]=?|==|~/?|<[<=]?|>[>=]?|unary-)";
-
-  /**
-   * Source of RegExp matching Dart reserved words.
-   * From sdk/lib/internal/symbol.dart.
-   */
-  static String _RESERVED_WORD_RE =
-      "(?:assert|break|c(?:a(?:se|tch)|lass|on(?:st|tinue))|d(?:efault|o)|e(?:lse|num|xtends)|f(?:alse|inal(?:ly)?|or)|i[fns]|n(?:ew|ull)|ret(?:hrow|urn)|s(?:uper|witch)|t(?:h(?:is|row)|r(?:ue|y))|v(?:ar|oid)|w(?:hile|ith))";
-
-  /**
-   * A graph in which the nodes are the constants, and the edges are from each
-   * constant to the other constants that are referenced by it.
-   */
-  DirectedGraph<ConstantEvaluationTarget> referenceGraph =
-      new DirectedGraph<ConstantEvaluationTarget>();
-
-  /**
-   * The elements whose constant values need to be computed.  Any elements
-   * which appear in [referenceGraph] but not in this set either belong to a
-   * different library cycle (and hence don't need to be recomputed) or were
-   * computed during a previous stage of resolution stage (e.g. constants
-   * associated with enums).
-   */
-  HashSet<ConstantEvaluationTarget> _constantsToCompute =
-      new HashSet<ConstantEvaluationTarget>();
-
-  /**
-   * The evaluation engine that does the work of evaluating instance creation
-   * expressions.
-   */
-  final ConstantEvaluationEngine evaluationEngine;
-
-  final AnalysisContext _context;
-
-  /**
-   * Initialize a newly created constant value computer. The [typeProvider] is
-   * the type provider used to access known types. The [declaredVariables] is
-   * the set of variables declared on the command line using '-D'.
-   */
-  ConstantValueComputer(this._context, TypeProvider typeProvider,
-      DeclaredVariables declaredVariables,
-      [ConstantEvaluationValidator validator, TypeSystem typeSystem])
-      : evaluationEngine = new ConstantEvaluationEngine(
-            typeProvider, declaredVariables,
-            validator: validator, typeSystem: typeSystem);
-
-  /**
-   * Add the constants in the given compilation [unit] to the list of constants
-   * whose value needs to be computed.
-   */
-  void add(CompilationUnit unit, Source source, Source librarySource) {
-    ConstantFinder constantFinder =
-        new ConstantFinder(_context, source, librarySource);
-    unit.accept(constantFinder);
-    _constantsToCompute.addAll(constantFinder.constantsToCompute);
-  }
-
-  /**
-   * Compute values for all of the constants in the compilation units that were
-   * added.
-   */
-  void computeValues() {
-    for (ConstantEvaluationTarget constant in _constantsToCompute) {
-      referenceGraph.addNode(constant);
-      evaluationEngine.computeDependencies(constant,
-          (ConstantEvaluationTarget dependency) {
-        referenceGraph.addEdge(constant, dependency);
-      });
-    }
-    List<List<ConstantEvaluationTarget>> topologicalSort =
-        referenceGraph.computeTopologicalSort();
-    for (List<ConstantEvaluationTarget> constantsInCycle in topologicalSort) {
-      if (constantsInCycle.length == 1) {
-        ConstantEvaluationTarget constant = constantsInCycle[0];
-        if (!referenceGraph.getTails(constant).contains(constant)) {
-          _computeValueFor(constant);
-          continue;
-        }
-      }
-      for (ConstantEvaluationTarget constant in constantsInCycle) {
-        evaluationEngine.generateCycleError(constantsInCycle, constant);
-      }
-    }
-  }
-
-  /**
-   * Compute a value for the given [constant].
-   */
-  void _computeValueFor(ConstantEvaluationTarget constant) {
-    if (!_constantsToCompute.contains(constant)) {
-      // Element is in the dependency graph but should have been computed by
-      // a previous stage of analysis.
-      // TODO(paulberry): once we have moved over to the new task model, this
-      // should only occur for constants associated with enum members.  Once
-      // that happens we should add an assertion to verify that it doesn't
-      // occur in any other cases.
-      return;
-    }
-    evaluationEngine.computeConstantValue(constant);
-  }
-}
-
-/**
- * A visitor used to evaluate constant expressions to produce their compile-time
- * value. According to the Dart Language Specification: <blockquote> A constant
- * expression is one of the following:
- *
- * * A literal number.
- * * A literal boolean.
- * * A literal string where any interpolated expression is a compile-time
- *   constant that evaluates to a numeric, string or boolean value or to
- *   <b>null</b>.
- * * A literal symbol.
- * * <b>null</b>.
- * * A qualified reference to a static constant variable.
- * * An identifier expression that denotes a constant variable, class or type
- *   alias.
- * * A constant constructor invocation.
- * * A constant list literal.
- * * A constant map literal.
- * * A simple or qualified identifier denoting a top-level function or a static
- *   method.
- * * A parenthesized expression <i>(e)</i> where <i>e</i> is a constant
- *   expression.
- * * An expression of the form <i>identical(e<sub>1</sub>, e<sub>2</sub>)</i>
- *   where <i>e<sub>1</sub></i> and <i>e<sub>2</sub></i> are constant
- *   expressions and <i>identical()</i> is statically bound to the predefined
- *   dart function <i>identical()</i> discussed above.
- * * An expression of one of the forms <i>e<sub>1</sub> == e<sub>2</sub></i> or
- *   <i>e<sub>1</sub> != e<sub>2</sub></i> where <i>e<sub>1</sub></i> and
- *   <i>e<sub>2</sub></i> are constant expressions that evaluate to a numeric,
- *   string or boolean value.
- * * An expression of one of the forms <i>!e</i>, <i>e<sub>1</sub> &amp;&amp;
- *   e<sub>2</sub></i> or <i>e<sub>1</sub> || e<sub>2</sub></i>, where <i>e</i>,
- *   <i>e1</sub></i> and <i>e2</sub></i> are constant expressions that evaluate
- *   to a boolean value.
- * * An expression of one of the forms <i>~e</i>, <i>e<sub>1</sub> ^
- *   e<sub>2</sub></i>, <i>e<sub>1</sub> &amp; e<sub>2</sub></i>,
- *   <i>e<sub>1</sub> | e<sub>2</sub></i>, <i>e<sub>1</sub> &gt;&gt;
- *   e<sub>2</sub></i> or <i>e<sub>1</sub> &lt;&lt; e<sub>2</sub></i>, where
- *   <i>e</i>, <i>e<sub>1</sub></i> and <i>e<sub>2</sub></i> are constant
- *   expressions that evaluate to an integer value or to <b>null</b>.
- * * An expression of one of the forms <i>-e</i>, <i>e<sub>1</sub> +
- *   e<sub>2</sub></i>, <i>e<sub>1</sub> - e<sub>2</sub></i>, <i>e<sub>1</sub> *
- *   e<sub>2</sub></i>, <i>e<sub>1</sub> / e<sub>2</sub></i>, <i>e<sub>1</sub>
- *   ~/ e<sub>2</sub></i>, <i>e<sub>1</sub> &gt; e<sub>2</sub></i>,
- *   <i>e<sub>1</sub> &lt; e<sub>2</sub></i>, <i>e<sub>1</sub> &gt;=
- *   e<sub>2</sub></i>, <i>e<sub>1</sub> &lt;= e<sub>2</sub></i> or
- *   <i>e<sub>1</sub> % e<sub>2</sub></i>, where <i>e</i>, <i>e<sub>1</sub></i>
- *   and <i>e<sub>2</sub></i> are constant expressions that evaluate to a
- *   numeric value or to <b>null</b>.
- * * An expression of the form <i>e<sub>1</sub> ? e<sub>2</sub> :
- *   e<sub>3</sub></i> where <i>e<sub>1</sub></i>, <i>e<sub>2</sub></i> and
- *   <i>e<sub>3</sub></i> are constant expressions, and <i>e<sub>1</sub></i>
- *   evaluates to a boolean value.
- * </blockquote>
- */
-class ConstantVisitor extends UnifyingAstVisitor<DartObjectImpl> {
-  /**
-   * The type provider used to access the known types.
-   */
-  final ConstantEvaluationEngine evaluationEngine;
-
-  final HashMap<String, DartObjectImpl> _lexicalEnvironment;
-
-  /**
-   * Error reporter that we use to report errors accumulated while computing the
-   * constant.
-   */
-  final ErrorReporter _errorReporter;
-
-  /**
-   * Helper class used to compute constant values.
-   */
-  DartObjectComputer _dartObjectComputer;
-
-  /**
-   * Initialize a newly created constant visitor. The [evaluationEngine] is
-   * used to evaluate instance creation expressions. The [lexicalEnvironment]
-   * is a map containing values which should override identifiers, or `null` if
-   * no overriding is necessary. The [_errorReporter] is used to report errors
-   * found during evaluation.  The [validator] is used by unit tests to verify
-   * correct dependency analysis.
-   */
-  ConstantVisitor(this.evaluationEngine, this._errorReporter,
-      {HashMap<String, DartObjectImpl> lexicalEnvironment})
-      : _lexicalEnvironment = lexicalEnvironment {
-    this._dartObjectComputer =
-        new DartObjectComputer(_errorReporter, evaluationEngine.typeProvider);
-  }
-
-  /**
-   * Convenience getter to gain access to the [evalationEngine]'s type
-   * provider.
-   */
-  TypeProvider get _typeProvider => evaluationEngine.typeProvider;
-
-  /**
-   * Convenience getter to gain access to the [evaluationEngine]'s type system.
-   */
-  TypeSystem get _typeSystem => evaluationEngine.typeSystem;
-
-  @override
-  DartObjectImpl visitAdjacentStrings(AdjacentStrings node) {
-    DartObjectImpl result = null;
-    for (StringLiteral string in node.strings) {
-      if (result == null) {
-        result = string.accept(this);
-      } else {
-        result =
-            _dartObjectComputer.concatenate(node, result, string.accept(this));
-      }
-    }
-    return result;
-  }
-
-  @override
-  DartObjectImpl visitBinaryExpression(BinaryExpression node) {
-    DartObjectImpl leftResult = node.leftOperand.accept(this);
-    DartObjectImpl rightResult = node.rightOperand.accept(this);
-    TokenType operatorType = node.operator.type;
-    // 'null' is almost never good operand
-    if (operatorType != TokenType.BANG_EQ &&
-        operatorType != TokenType.EQ_EQ &&
-        operatorType != TokenType.QUESTION_QUESTION) {
-      if (leftResult != null && leftResult.isNull ||
-          rightResult != null && rightResult.isNull) {
-        _error(node, CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-        return null;
-      }
-    }
-    // evaluate operator
-    while (true) {
-      if (operatorType == TokenType.AMPERSAND) {
-        return _dartObjectComputer.bitAnd(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.AMPERSAND_AMPERSAND) {
-        return _dartObjectComputer.logicalAnd(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.BANG_EQ) {
-        return _dartObjectComputer.notEqual(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.BAR) {
-        return _dartObjectComputer.bitOr(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.BAR_BAR) {
-        return _dartObjectComputer.logicalOr(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.CARET) {
-        return _dartObjectComputer.bitXor(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.EQ_EQ) {
-        return _dartObjectComputer.equalEqual(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.GT) {
-        return _dartObjectComputer.greaterThan(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.GT_EQ) {
-        return _dartObjectComputer.greaterThanOrEqual(
-            node, leftResult, rightResult);
-      } else if (operatorType == TokenType.GT_GT) {
-        return _dartObjectComputer.shiftRight(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.LT) {
-        return _dartObjectComputer.lessThan(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.LT_EQ) {
-        return _dartObjectComputer.lessThanOrEqual(
-            node, leftResult, rightResult);
-      } else if (operatorType == TokenType.LT_LT) {
-        return _dartObjectComputer.shiftLeft(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.MINUS) {
-        return _dartObjectComputer.minus(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.PERCENT) {
-        return _dartObjectComputer.remainder(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.PLUS) {
-        return _dartObjectComputer.add(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.STAR) {
-        return _dartObjectComputer.times(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.SLASH) {
-        return _dartObjectComputer.divide(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.TILDE_SLASH) {
-        return _dartObjectComputer.integerDivide(node, leftResult, rightResult);
-      } else if (operatorType == TokenType.QUESTION_QUESTION) {
-        return _dartObjectComputer.questionQuestion(
-            node, leftResult, rightResult);
-      } else {
-        // TODO(brianwilkerson) Figure out which error to report.
-        _error(node, null);
-        return null;
-      }
-      break;
-    }
-  }
-
-  @override
-  DartObjectImpl visitBooleanLiteral(BooleanLiteral node) =>
-      new DartObjectImpl(_typeProvider.boolType, BoolState.from(node.value));
-
-  @override
-  DartObjectImpl visitConditionalExpression(ConditionalExpression node) {
-    Expression condition = node.condition;
-    DartObjectImpl conditionResult = condition.accept(this);
-    DartObjectImpl thenResult = node.thenExpression.accept(this);
-    DartObjectImpl elseResult = node.elseExpression.accept(this);
-    if (conditionResult == null) {
-      return conditionResult;
-    } else if (!conditionResult.isBool) {
-      _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.CONST_EVAL_TYPE_BOOL, condition);
-      return null;
-    } else if (thenResult == null) {
-      return thenResult;
-    } else if (elseResult == null) {
-      return elseResult;
-    }
-    conditionResult =
-        _dartObjectComputer.applyBooleanConversion(condition, conditionResult);
-    if (conditionResult == null) {
-      return conditionResult;
-    }
-    if (conditionResult.toBoolValue() == true) {
-      return thenResult;
-    } else if (conditionResult.toBoolValue() == false) {
-      return elseResult;
-    }
-    ParameterizedType thenType = thenResult.type;
-    ParameterizedType elseType = elseResult.type;
-    return new DartObjectImpl.validWithUnknownValue(
-        _typeSystem.getLeastUpperBound(_typeProvider, thenType, elseType)
-        as InterfaceType);
-  }
-
-  @override
-  DartObjectImpl visitDoubleLiteral(DoubleLiteral node) =>
-      new DartObjectImpl(_typeProvider.doubleType, new DoubleState(node.value));
-
-  @override
-  DartObjectImpl visitInstanceCreationExpression(
-      InstanceCreationExpression node) {
-    if (!node.isConst) {
-      // TODO(brianwilkerson) Figure out which error to report.
-      _error(node, null);
-      return null;
-    }
-    ConstructorElement constructor = node.staticElement;
-    if (constructor == null) {
-      // Couldn't resolve the constructor so we can't compute a value.  No
-      // problem - the error has already been reported.
-      return null;
-    }
-    return evaluationEngine.evaluateConstructorCall(
-        node, node.argumentList.arguments, constructor, this, _errorReporter);
-  }
-
-  @override
-  DartObjectImpl visitIntegerLiteral(IntegerLiteral node) =>
-      new DartObjectImpl(_typeProvider.intType, new IntState(node.value));
-
-  @override
-  DartObjectImpl visitInterpolationExpression(InterpolationExpression node) {
-    DartObjectImpl result = node.expression.accept(this);
-    if (result != null && !result.isBoolNumStringOrNull) {
-      _error(node, CompileTimeErrorCode.CONST_EVAL_TYPE_BOOL_NUM_STRING);
-      return null;
-    }
-    return _dartObjectComputer.performToString(node, result);
-  }
-
-  @override
-  DartObjectImpl visitInterpolationString(InterpolationString node) =>
-      new DartObjectImpl(_typeProvider.stringType, new StringState(node.value));
-
-  @override
-  DartObjectImpl visitListLiteral(ListLiteral node) {
-    if (node.constKeyword == null) {
-      _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.MISSING_CONST_IN_LIST_LITERAL, node);
-      return null;
-    }
-    bool errorOccurred = false;
-    List<DartObjectImpl> elements = new List<DartObjectImpl>();
-    for (Expression element in node.elements) {
-      DartObjectImpl elementResult = element.accept(this);
-      if (elementResult == null) {
-        errorOccurred = true;
-      } else {
-        elements.add(elementResult);
-      }
-    }
-    if (errorOccurred) {
-      return null;
-    }
-    DartType elementType = _typeProvider.dynamicType;
-    if (node.typeArguments != null &&
-        node.typeArguments.arguments.length == 1) {
-      DartType type = node.typeArguments.arguments[0].type;
-      if (type != null) {
-        elementType = type;
-      }
-    }
-    InterfaceType listType = _typeProvider.listType.instantiate([elementType]);
-    return new DartObjectImpl(listType, new ListState(elements));
-  }
-
-  @override
-  DartObjectImpl visitMapLiteral(MapLiteral node) {
-    if (node.constKeyword == null) {
-      _errorReporter.reportErrorForNode(
-          CompileTimeErrorCode.MISSING_CONST_IN_MAP_LITERAL, node);
-      return null;
-    }
-    bool errorOccurred = false;
-    LinkedHashMap<DartObjectImpl, DartObjectImpl> map =
-        new LinkedHashMap<DartObjectImpl, DartObjectImpl>();
-    for (MapLiteralEntry entry in node.entries) {
-      DartObjectImpl keyResult = entry.key.accept(this);
-      DartObjectImpl valueResult = entry.value.accept(this);
-      if (keyResult == null || valueResult == null) {
-        errorOccurred = true;
-      } else {
-        map[keyResult] = valueResult;
-      }
-    }
-    if (errorOccurred) {
-      return null;
-    }
-    DartType keyType = _typeProvider.dynamicType;
-    DartType valueType = _typeProvider.dynamicType;
-    if (node.typeArguments != null &&
-        node.typeArguments.arguments.length == 2) {
-      DartType keyTypeCandidate = node.typeArguments.arguments[0].type;
-      if (keyTypeCandidate != null) {
-        keyType = keyTypeCandidate;
-      }
-      DartType valueTypeCandidate = node.typeArguments.arguments[1].type;
-      if (valueTypeCandidate != null) {
-        valueType = valueTypeCandidate;
-      }
-    }
-    InterfaceType mapType =
-        _typeProvider.mapType.instantiate([keyType, valueType]);
-    return new DartObjectImpl(mapType, new MapState(map));
-  }
-
-  @override
-  DartObjectImpl visitMethodInvocation(MethodInvocation node) {
-    Element element = node.methodName.staticElement;
-    if (element is FunctionElement) {
-      FunctionElement function = element;
-      if (function.name == "identical") {
-        NodeList<Expression> arguments = node.argumentList.arguments;
-        if (arguments.length == 2) {
-          Element enclosingElement = function.enclosingElement;
-          if (enclosingElement is CompilationUnitElement) {
-            LibraryElement library = enclosingElement.library;
-            if (library.isDartCore) {
-              DartObjectImpl leftArgument = arguments[0].accept(this);
-              DartObjectImpl rightArgument = arguments[1].accept(this);
-              return _dartObjectComputer.isIdentical(
-                  node, leftArgument, rightArgument);
-            }
-          }
-        }
-      }
-    }
-    // TODO(brianwilkerson) Figure out which error to report.
-    _error(node, null);
-    return null;
-  }
-
-  @override
-  DartObjectImpl visitNamedExpression(NamedExpression node) =>
-      node.expression.accept(this);
-
-  @override
-  DartObjectImpl visitNode(AstNode node) {
-    // TODO(brianwilkerson) Figure out which error to report.
-    _error(node, null);
-    return null;
-  }
-
-  @override
-  DartObjectImpl visitNullLiteral(NullLiteral node) => _typeProvider.nullObject;
-
-  @override
-  DartObjectImpl visitParenthesizedExpression(ParenthesizedExpression node) =>
-      node.expression.accept(this);
-
-  @override
-  DartObjectImpl visitPrefixedIdentifier(PrefixedIdentifier node) {
-    SimpleIdentifier prefixNode = node.prefix;
-    Element prefixElement = prefixNode.staticElement;
-    // String.length
-    if (prefixElement is! PrefixElement && prefixElement is! ClassElement) {
-      DartObjectImpl prefixResult = node.prefix.accept(this);
-      if (_isStringLength(prefixResult, node.identifier)) {
-        return prefixResult.stringLength(_typeProvider);
-      }
-    }
-    // importPrefix.CONST
-    if (prefixElement is! PrefixElement) {
-      DartObjectImpl prefixResult = prefixNode.accept(this);
-      if (prefixResult == null) {
-        // The error has already been reported.
-        return null;
-      }
-    }
-    // validate prefixed identifier
-    return _getConstantValue(node, node.staticElement);
-  }
-
-  @override
-  DartObjectImpl visitPrefixExpression(PrefixExpression node) {
-    DartObjectImpl operand = node.operand.accept(this);
-    if (operand != null && operand.isNull) {
-      _error(node, CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-      return null;
-    }
-    while (true) {
-      if (node.operator.type == TokenType.BANG) {
-        return _dartObjectComputer.logicalNot(node, operand);
-      } else if (node.operator.type == TokenType.TILDE) {
-        return _dartObjectComputer.bitNot(node, operand);
-      } else if (node.operator.type == TokenType.MINUS) {
-        return _dartObjectComputer.negated(node, operand);
-      } else {
-        // TODO(brianwilkerson) Figure out which error to report.
-        _error(node, null);
-        return null;
-      }
-      break;
-    }
-  }
-
-  @override
-  DartObjectImpl visitPropertyAccess(PropertyAccess node) {
-    if (node.target != null) {
-      DartObjectImpl prefixResult = node.target.accept(this);
-      if (_isStringLength(prefixResult, node.propertyName)) {
-        return prefixResult.stringLength(_typeProvider);
-      }
-    }
-    return _getConstantValue(node, node.propertyName.staticElement);
-  }
-
-  @override
-  DartObjectImpl visitSimpleIdentifier(SimpleIdentifier node) {
-    if (_lexicalEnvironment != null &&
-        _lexicalEnvironment.containsKey(node.name)) {
-      return _lexicalEnvironment[node.name];
-    }
-    return _getConstantValue(node, node.staticElement);
-  }
-
-  @override
-  DartObjectImpl visitSimpleStringLiteral(SimpleStringLiteral node) =>
-      new DartObjectImpl(_typeProvider.stringType, new StringState(node.value));
-
-  @override
-  DartObjectImpl visitStringInterpolation(StringInterpolation node) {
-    DartObjectImpl result = null;
-    bool first = true;
-    for (InterpolationElement element in node.elements) {
-      if (first) {
-        result = element.accept(this);
-        first = false;
-      } else {
-        result =
-            _dartObjectComputer.concatenate(node, result, element.accept(this));
-      }
-    }
-    return result;
-  }
-
-  @override
-  DartObjectImpl visitSymbolLiteral(SymbolLiteral node) {
-    StringBuffer buffer = new StringBuffer();
-    List<Token> components = node.components;
-    for (int i = 0; i < components.length; i++) {
-      if (i > 0) {
-        buffer.writeCharCode(0x2E);
-      }
-      buffer.write(components[i].lexeme);
-    }
-    return new DartObjectImpl(
-        _typeProvider.symbolType, new SymbolState(buffer.toString()));
-  }
-
-  /**
-   * Create an error associated with the given [node]. The error will have the
-   * given error [code].
-   */
-  void _error(AstNode node, ErrorCode code) {
-    _errorReporter.reportErrorForNode(
-        code == null ? CompileTimeErrorCode.INVALID_CONSTANT : code, node);
-  }
-
-  /**
-   * Return the constant value of the static constant represented by the given
-   * [element]. The [node] is the node to be used if an error needs to be
-   * reported.
-   */
-  DartObjectImpl _getConstantValue(AstNode node, Element element) {
-    if (element is PropertyAccessorElement) {
-      element = (element as PropertyAccessorElement).variable;
-    }
-    if (element is VariableElementImpl) {
-      VariableElementImpl variableElementImpl = element;
-      evaluationEngine.validator.beforeGetEvaluationResult(element);
-      EvaluationResultImpl value = variableElementImpl.evaluationResult;
-      if (variableElementImpl.isConst && value != null) {
-        return value.value;
-      }
-    } else if (element is ExecutableElement) {
-      ExecutableElement function = element;
-      if (function.isStatic) {
-        ParameterizedType functionType = function.type;
-        if (functionType == null) {
-          functionType = _typeProvider.functionType;
-        }
-        return new DartObjectImpl(functionType, new FunctionState(function));
-      }
-    } else if (element is ClassElement ||
-        element is FunctionTypeAliasElement ||
-        element is DynamicElementImpl) {
-      return new DartObjectImpl(_typeProvider.typeType, new TypeState(element));
-    }
-    // TODO(brianwilkerson) Figure out which error to report.
-    _error(node, null);
-    return null;
-  }
-
-  /**
-   * Return `true` if the given [targetResult] represents a string and the
-   * [identifier] is "length".
-   */
-  bool _isStringLength(
-      DartObjectImpl targetResult, SimpleIdentifier identifier) {
-    if (targetResult == null || targetResult.type != _typeProvider.stringType) {
-      return false;
-    }
-    return identifier.name == 'length';
-  }
-
-  /**
-   * Return the value of the given [expression], or a representation of 'null'
-   * if the expression cannot be evaluated.
-   */
-  DartObjectImpl _valueOf(Expression expression) {
-    DartObjectImpl expressionValue = expression.accept(this);
-    if (expressionValue != null) {
-      return expressionValue;
-    }
-    return _typeProvider.nullObject;
-  }
-}
-
-/**
- * A utility class that contains methods for manipulating instances of a Dart
- * class and for collecting errors during evaluation.
- */
-class DartObjectComputer {
-  /**
-   * The error reporter that we are using to collect errors.
-   */
-  final ErrorReporter _errorReporter;
-
-  /**
-   * The type provider used to create objects of the appropriate types, and to
-   * identify when an object is of a built-in type.
-   */
-  final TypeProvider _typeProvider;
-
-  DartObjectComputer(this._errorReporter, this._typeProvider);
-
-  DartObjectImpl add(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.add(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-        return null;
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Return the result of applying boolean conversion to the [evaluationResult].
-   * The [node] is the node against which errors should be reported.
-   */
-  DartObjectImpl applyBooleanConversion(
-      AstNode node, DartObjectImpl evaluationResult) {
-    if (evaluationResult != null) {
-      try {
-        return evaluationResult.convertToBool(_typeProvider);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl bitAnd(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.bitAnd(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl bitNot(Expression node, DartObjectImpl evaluationResult) {
-    if (evaluationResult != null) {
-      try {
-        return evaluationResult.bitNot(_typeProvider);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl bitOr(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.bitOr(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl bitXor(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.bitXor(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl concatenate(Expression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.concatenate(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl divide(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.divide(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl equalEqual(Expression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.equalEqual(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl greaterThan(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.greaterThan(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl greaterThanOrEqual(BinaryExpression node,
-      DartObjectImpl leftOperand, DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.greaterThanOrEqual(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl integerDivide(BinaryExpression node,
-      DartObjectImpl leftOperand, DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.integerDivide(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl isIdentical(Expression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.isIdentical(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl lessThan(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.lessThan(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl lessThanOrEqual(BinaryExpression node,
-      DartObjectImpl leftOperand, DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.lessThanOrEqual(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl logicalAnd(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.logicalAnd(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl logicalNot(Expression node, DartObjectImpl evaluationResult) {
-    if (evaluationResult != null) {
-      try {
-        return evaluationResult.logicalNot(_typeProvider);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl logicalOr(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.logicalOr(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl minus(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.minus(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl negated(Expression node, DartObjectImpl evaluationResult) {
-    if (evaluationResult != null) {
-      try {
-        return evaluationResult.negated(_typeProvider);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl notEqual(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.notEqual(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl performToString(
-      AstNode node, DartObjectImpl evaluationResult) {
-    if (evaluationResult != null) {
-      try {
-        return evaluationResult.performToString(_typeProvider);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl questionQuestion(Expression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      if (leftOperand.isNull) {
-        return rightOperand;
-      }
-      return leftOperand;
-    }
-    return null;
-  }
-
-  DartObjectImpl remainder(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.remainder(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl shiftLeft(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.shiftLeft(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  DartObjectImpl shiftRight(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.shiftRight(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-
-  /**
-   * Return the result of invoking the 'length' getter on the
-   * [evaluationResult]. The [node] is the node against which errors should be
-   * reported.
-   */
-  EvaluationResultImpl stringLength(
-      Expression node, EvaluationResultImpl evaluationResult) {
-    if (evaluationResult.value != null) {
-      try {
-        return new EvaluationResultImpl(
-            evaluationResult.value.stringLength(_typeProvider));
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return new EvaluationResultImpl(null);
-  }
-
-  DartObjectImpl times(BinaryExpression node, DartObjectImpl leftOperand,
-      DartObjectImpl rightOperand) {
-    if (leftOperand != null && rightOperand != null) {
-      try {
-        return leftOperand.times(_typeProvider, rightOperand);
-      } on EvaluationException catch (exception) {
-        _errorReporter.reportErrorForNode(exception.errorCode, node);
-      }
-    }
-    return null;
-  }
-}
-
-/**
- * An instance of a Dart class.
- */
-class DartObjectImpl implements DartObject {
-  /**
-   * An empty list of objects.
-   */
-  static const List<DartObjectImpl> EMPTY_LIST = const <DartObjectImpl>[];
-
-  /**
-   * The run-time type of this object.
-   */
-  @override
-  final ParameterizedType type;
-
-  /**
-   * The state of the object.
-   */
-  final InstanceState _state;
-
-  /**
-   * Initialize a newly created object to have the given [type] and [_state].
-   */
-  DartObjectImpl(this.type, this._state);
-
-  /**
-   * Create an object to represent an unknown value.
-   */
-  factory DartObjectImpl.validWithUnknownValue(InterfaceType type) {
-    if (type.element.library.isDartCore) {
-      String typeName = type.name;
-      if (typeName == "bool") {
-        return new DartObjectImpl(type, BoolState.UNKNOWN_VALUE);
-      } else if (typeName == "double") {
-        return new DartObjectImpl(type, DoubleState.UNKNOWN_VALUE);
-      } else if (typeName == "int") {
-        return new DartObjectImpl(type, IntState.UNKNOWN_VALUE);
-      } else if (typeName == "String") {
-        return new DartObjectImpl(type, StringState.UNKNOWN_VALUE);
-      }
-    }
-    return new DartObjectImpl(type, GenericState.UNKNOWN_VALUE);
-  }
-
-  HashMap<String, DartObjectImpl> get fields => _state.fields;
-
-  @override
-  int get hashCode => JenkinsSmiHash.hash2(type.hashCode, _state.hashCode);
-
-  @override
-  bool get hasKnownValue => !_state.isUnknown;
-
-  /**
-   * Return `true` if this object represents an object whose type is 'bool'.
-   */
-  bool get isBool => _state.isBool;
-
-  /**
-   * Return `true` if this object represents an object whose type is either
-   * 'bool', 'num', 'String', or 'Null'.
-   */
-  bool get isBoolNumStringOrNull => _state.isBoolNumStringOrNull;
-
-  @override
-  bool get isNull => _state is NullState;
-
-  /**
-   * Return `true` if this object represents an unknown value.
-   */
-  bool get isUnknown => _state.isUnknown;
-
-  /**
-   * Return `true` if this object represents an instance of a user-defined
-   * class.
-   */
-  bool get isUserDefinedObject => _state is GenericState;
-
-  @override
-  bool operator ==(Object object) {
-    if (object is! DartObjectImpl) {
-      return false;
-    }
-    DartObjectImpl dartObject = object as DartObjectImpl;
-    return type == dartObject.type && _state == dartObject._state;
-  }
-
-  /**
-   * Return the result of invoking the '+' operator on this object with the
-   * given [rightOperand]. The [typeProvider] is the type provider used to find
-   * known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl add(TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    InstanceState result = _state.add(rightOperand._state);
-    if (result is IntState) {
-      return new DartObjectImpl(typeProvider.intType, result);
-    } else if (result is DoubleState) {
-      return new DartObjectImpl(typeProvider.doubleType, result);
-    } else if (result is NumState) {
-      return new DartObjectImpl(typeProvider.numType, result);
-    } else if (result is StringState) {
-      return new DartObjectImpl(typeProvider.stringType, result);
-    }
-    // We should never get here.
-    throw new IllegalStateException("add returned a ${result.runtimeType}");
-  }
-
-  /**
-   * Return the result of invoking the '&' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl bitAnd(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.intType, _state.bitAnd(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '~' operator on this object. The
-   * [typeProvider] is the type provider used to find known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl bitNot(TypeProvider typeProvider) =>
-      new DartObjectImpl(typeProvider.intType, _state.bitNot());
-
-  /**
-   * Return the result of invoking the '|' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl bitOr(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.intType, _state.bitOr(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '^' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl bitXor(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.intType, _state.bitXor(rightOperand._state));
-
-  /**
-   * Return the result of invoking the ' ' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl concatenate(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.stringType, _state.concatenate(rightOperand._state));
-
-  /**
-   * Return the result of applying boolean conversion to this object. The
-   * [typeProvider] is the type provider used to find known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl convertToBool(TypeProvider typeProvider) {
-    InterfaceType boolType = typeProvider.boolType;
-    if (identical(type, boolType)) {
-      return this;
-    }
-    return new DartObjectImpl(boolType, _state.convertToBool());
-  }
-
-  /**
-   * Return the result of invoking the '/' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for
-   * an object of this kind.
-   */
-  DartObjectImpl divide(
-      TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    InstanceState result = _state.divide(rightOperand._state);
-    if (result is IntState) {
-      return new DartObjectImpl(typeProvider.intType, result);
-    } else if (result is DoubleState) {
-      return new DartObjectImpl(typeProvider.doubleType, result);
-    } else if (result is NumState) {
-      return new DartObjectImpl(typeProvider.numType, result);
-    }
-    // We should never get here.
-    throw new IllegalStateException("divide returned a ${result.runtimeType}");
-  }
-
-  /**
-   * Return the result of invoking the '==' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl equalEqual(
-      TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    if (type != rightOperand.type) {
-      String typeName = type.name;
-      if (!(typeName == "bool" ||
-          typeName == "double" ||
-          typeName == "int" ||
-          typeName == "num" ||
-          typeName == "String" ||
-          typeName == "Null" ||
-          type.isDynamic)) {
-        throw new EvaluationException(
-            CompileTimeErrorCode.CONST_EVAL_TYPE_BOOL_NUM_STRING);
-      }
-    }
-    return new DartObjectImpl(
-        typeProvider.boolType, _state.equalEqual(rightOperand._state));
-  }
-
-  @override
-  DartObject getField(String name) {
-    if (_state is GenericState) {
-      return (_state as GenericState).fields[name];
-    }
-    return null;
-  }
-
-  /**
-   * Return the result of invoking the '&gt;' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl greaterThan(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.boolType, _state.greaterThan(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '&gt;=' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl greaterThanOrEqual(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(typeProvider.boolType,
-          _state.greaterThanOrEqual(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '~/' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl integerDivide(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.intType, _state.integerDivide(rightOperand._state));
-
-  /**
-   * Return the result of invoking the identical function on this object with
-   * the [rightOperand]. The [typeProvider] is the type provider used to find
-   * known types.
-   */
-  DartObjectImpl isIdentical(
-      TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    return new DartObjectImpl(
-        typeProvider.boolType, _state.isIdentical(rightOperand._state));
-  }
-
-  /**
-   * Return the result of invoking the '&lt;' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl lessThan(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.boolType, _state.lessThan(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '&lt;=' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl lessThanOrEqual(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.boolType, _state.lessThanOrEqual(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '&&' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl logicalAnd(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.boolType, _state.logicalAnd(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '!' operator on this object. The
-   * [typeProvider] is the type provider used to find known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl logicalNot(TypeProvider typeProvider) =>
-      new DartObjectImpl(typeProvider.boolType, _state.logicalNot());
-
-  /**
-   * Return the result of invoking the '||' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl logicalOr(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.boolType, _state.logicalOr(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '-' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl minus(TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    InstanceState result = _state.minus(rightOperand._state);
-    if (result is IntState) {
-      return new DartObjectImpl(typeProvider.intType, result);
-    } else if (result is DoubleState) {
-      return new DartObjectImpl(typeProvider.doubleType, result);
-    } else if (result is NumState) {
-      return new DartObjectImpl(typeProvider.numType, result);
-    }
-    // We should never get here.
-    throw new IllegalStateException("minus returned a ${result.runtimeType}");
-  }
-
-  /**
-   * Return the result of invoking the '-' operator on this object. The
-   * [typeProvider] is the type provider used to find known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl negated(TypeProvider typeProvider) {
-    InstanceState result = _state.negated();
-    if (result is IntState) {
-      return new DartObjectImpl(typeProvider.intType, result);
-    } else if (result is DoubleState) {
-      return new DartObjectImpl(typeProvider.doubleType, result);
-    } else if (result is NumState) {
-      return new DartObjectImpl(typeProvider.numType, result);
-    }
-    // We should never get here.
-    throw new IllegalStateException("negated returned a ${result.runtimeType}");
-  }
-
-  /**
-   * Return the result of invoking the '!=' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl notEqual(
-      TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    if (type != rightOperand.type) {
-      String typeName = type.name;
-      if (typeName != "bool" &&
-          typeName != "double" &&
-          typeName != "int" &&
-          typeName != "num" &&
-          typeName != "String") {
-        return new DartObjectImpl(typeProvider.boolType, BoolState.TRUE_STATE);
-      }
-    }
-    return new DartObjectImpl(typeProvider.boolType,
-        _state.equalEqual(rightOperand._state).logicalNot());
-  }
-
-  /**
-   * Return the result of converting this object to a 'String'. The
-   * [typeProvider] is the type provider used to find known types.
-   *
-   * Throws an [EvaluationException] if the object cannot be converted to a
-   * 'String'.
-   */
-  DartObjectImpl performToString(TypeProvider typeProvider) {
-    InterfaceType stringType = typeProvider.stringType;
-    if (identical(type, stringType)) {
-      return this;
-    }
-    return new DartObjectImpl(stringType, _state.convertToString());
-  }
-
-  /**
-   * Return the result of invoking the '%' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl remainder(
-      TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    InstanceState result = _state.remainder(rightOperand._state);
-    if (result is IntState) {
-      return new DartObjectImpl(typeProvider.intType, result);
-    } else if (result is DoubleState) {
-      return new DartObjectImpl(typeProvider.doubleType, result);
-    } else if (result is NumState) {
-      return new DartObjectImpl(typeProvider.numType, result);
-    }
-    // We should never get here.
-    throw new IllegalStateException(
-        "remainder returned a ${result.runtimeType}");
-  }
-
-  /**
-   * Return the result of invoking the '&lt;&lt;' operator on this object with
-   * the [rightOperand]. The [typeProvider] is the type provider used to find
-   * known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl shiftLeft(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.intType, _state.shiftLeft(rightOperand._state));
-
-  /**
-   * Return the result of invoking the '&gt;&gt;' operator on this object with
-   * the [rightOperand]. The [typeProvider] is the type provider used to find
-   * known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl shiftRight(
-          TypeProvider typeProvider, DartObjectImpl rightOperand) =>
-      new DartObjectImpl(
-          typeProvider.intType, _state.shiftRight(rightOperand._state));
-
-  /**
-   * Return the result of invoking the 'length' getter on this object. The
-   * [typeProvider] is the type provider used to find known types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl stringLength(TypeProvider typeProvider) =>
-      new DartObjectImpl(typeProvider.intType, _state.stringLength());
-
-  /**
-   * Return the result of invoking the '*' operator on this object with the
-   * [rightOperand]. The [typeProvider] is the type provider used to find known
-   * types.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  DartObjectImpl times(TypeProvider typeProvider, DartObjectImpl rightOperand) {
-    InstanceState result = _state.times(rightOperand._state);
-    if (result is IntState) {
-      return new DartObjectImpl(typeProvider.intType, result);
-    } else if (result is DoubleState) {
-      return new DartObjectImpl(typeProvider.doubleType, result);
-    } else if (result is NumState) {
-      return new DartObjectImpl(typeProvider.numType, result);
-    }
-    // We should never get here.
-    throw new IllegalStateException("times returned a ${result.runtimeType}");
-  }
-
-  @override
-  bool toBoolValue() {
-    if (_state is BoolState) {
-      return (_state as BoolState).value;
-    }
-    return null;
-  }
-
-  @override
-  double toDoubleValue() {
-    if (_state is DoubleState) {
-      return (_state as DoubleState).value;
-    }
-    return null;
-  }
-
-  @override
-  int toIntValue() {
-    if (_state is IntState) {
-      return (_state as IntState).value;
-    }
-    return null;
-  }
-
-  @override
-  List<DartObject> toListValue() {
-    if (_state is ListState) {
-      return (_state as ListState)._elements;
-    }
-    return null;
-  }
-
-  @override
-  Map<DartObject, DartObject> toMapValue() {
-    if (_state is MapState) {
-      return (_state as MapState)._entries;
-    }
-    return null;
-  }
-
-  @override
-  String toString() => "${type.displayName} ($_state)";
-
-  @override
-  String toStringValue() {
-    if (_state is StringState) {
-      return (_state as StringState).value;
-    }
-    return null;
-  }
-
-  @override
-  String toSymbolValue() {
-    if (_state is SymbolState) {
-      return (_state as SymbolState).value;
-    }
-    return null;
-  }
-
-  @override
-  DartType toTypeValue() {
-    if (_state is TypeState) {
-      Element element = (_state as TypeState)._element;
-      if (element is TypeDefiningElement) {
-        return element.type;
-      }
-    }
-    return null;
-  }
-}
-
-/**
- * An object used to provide access to the values of variables that have been
- * defined on the command line using the `-D` option.
- */
-class DeclaredVariables {
-  /**
-   * A table mapping the names of declared variables to their values.
-   */
-  HashMap<String, String> _declaredVariables = new HashMap<String, String>();
-
-  /**
-   * Define a variable with the given [name] to have the given [value].
-   */
-  void define(String name, String value) {
-    _declaredVariables[name] = value;
-  }
-
-  /**
-   * Return the value of the variable with the given [name] interpreted as a
-   * 'boolean' value. If the variable is not defined (or [name] is `null`), a
-   * DartObject representing "unknown" is returned. If the value cannot be
-   * parsed as a boolean, a DartObject representing 'null' is returned. The
-   * [typeProvider] is the type provider used to find the type 'bool'.
-   */
-  DartObject getBool(TypeProvider typeProvider, String name) {
-    String value = _declaredVariables[name];
-    if (value == null) {
-      return new DartObjectImpl(typeProvider.boolType, BoolState.UNKNOWN_VALUE);
-    }
-    if (value == "true") {
-      return new DartObjectImpl(typeProvider.boolType, BoolState.TRUE_STATE);
-    } else if (value == "false") {
-      return new DartObjectImpl(typeProvider.boolType, BoolState.FALSE_STATE);
-    }
-    return new DartObjectImpl(typeProvider.nullType, NullState.NULL_STATE);
-  }
-
-  /**
-   * Return the value of the variable with the given [name] interpreted as an
-   * integer value. If the variable is not defined (or [name] is `null`), a
-   * DartObject representing "unknown" is returned. If the value cannot be
-   * parsed as an integer, a DartObject representing 'null' is returned.
-   */
-  DartObject getInt(TypeProvider typeProvider, String name) {
-    String value = _declaredVariables[name];
-    if (value == null) {
-      return new DartObjectImpl(typeProvider.intType, IntState.UNKNOWN_VALUE);
-    }
-    int bigInteger;
-    try {
-      bigInteger = int.parse(value);
-    } on FormatException {
-      return new DartObjectImpl(typeProvider.nullType, NullState.NULL_STATE);
-    }
-    return new DartObjectImpl(typeProvider.intType, new IntState(bigInteger));
-  }
-
-  /**
-   * Return the value of the variable with the given [name] interpreted as a
-   * String value, or `null` if the variable is not defined. Return the value of
-   * the variable with the given name interpreted as a String value. If the
-   * variable is not defined (or [name] is `null`), a DartObject representing
-   * "unknown" is returned. The [typeProvider] is the type provider used to find
-   * the type 'String'.
-   */
-  DartObject getString(TypeProvider typeProvider, String name) {
-    String value = _declaredVariables[name];
-    if (value == null) {
-      return new DartObjectImpl(
-          typeProvider.stringType, StringState.UNKNOWN_VALUE);
-    }
-    return new DartObjectImpl(typeProvider.stringType, new StringState(value));
-  }
-}
-
-/**
- * The state of an object representing a double.
- */
-class DoubleState extends NumState {
-  /**
-   * A state that can be used to represent a double whose value is not known.
-   */
-  static DoubleState UNKNOWN_VALUE = new DoubleState(null);
-
-  /**
-   * The value of this instance.
-   */
-  final double value;
-
-  /**
-   * Initialize a newly created state to represent a double with the given
-   * [value].
-   */
-  DoubleState(this.value);
-
-  @override
-  int get hashCode => value == null ? 0 : value.hashCode;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  bool get isUnknown => value == null;
-
-  @override
-  String get typeName => "double";
-
-  @override
-  bool operator ==(Object object) =>
-      object is DoubleState && (value == object.value);
-
-  @override
-  NumState add(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value + rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value + rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  StringState convertToString() {
-    if (value == null) {
-      return StringState.UNKNOWN_VALUE;
-    }
-    return new StringState(value.toString());
-  }
-
-  @override
-  NumState divide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value / rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value / rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState greaterThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value > rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value > rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState greaterThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value >= rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value >= rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState integerDivide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return IntState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return IntState.UNKNOWN_VALUE;
-      }
-      double result = value / rightValue.toDouble();
-      return new IntState(result.toInt());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return IntState.UNKNOWN_VALUE;
-      }
-      double result = value / rightValue;
-      return new IntState(result.toInt());
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return IntState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value == rightValue);
-    } else if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value == rightValue.toDouble());
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.FALSE_STATE;
-  }
-
-  @override
-  BoolState lessThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value < rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value < rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState lessThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value <= rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value <= rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  NumState minus(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value - rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value - rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  NumState negated() {
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    return new DoubleState(-(value));
-  }
-
-  @override
-  NumState remainder(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value % rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value % rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  NumState times(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value * rightValue.toDouble());
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new DoubleState(value * rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  String toString() => value == null ? "-unknown-" : value.toString();
-}
-
-/**
- * The state of an object representing a Dart object for which there is no type
- * information.
- */
-class DynamicState extends InstanceState {
-  /**
-   * The unique instance of this class.
-   */
-  static DynamicState DYNAMIC_STATE = new DynamicState();
-
-  @override
-  bool get isBool => true;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  String get typeName => "dynamic";
-
-  @override
-  NumState add(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return _unknownNum(rightOperand);
-  }
-
-  @override
-  IntState bitAnd(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  IntState bitNot() => IntState.UNKNOWN_VALUE;
-
-  @override
-  IntState bitOr(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  IntState bitXor(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  StringState concatenate(InstanceState rightOperand) {
-    assertString(rightOperand);
-    return StringState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState convertToBool() => BoolState.UNKNOWN_VALUE;
-
-  @override
-  StringState convertToString() => StringState.UNKNOWN_VALUE;
-
-  @override
-  NumState divide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return _unknownNum(rightOperand);
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState greaterThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState greaterThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  IntState integerDivide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState lessThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState lessThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState logicalAnd(InstanceState rightOperand) {
-    assertBool(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState logicalNot() => BoolState.UNKNOWN_VALUE;
-
-  @override
-  BoolState logicalOr(InstanceState rightOperand) {
-    assertBool(rightOperand);
-    return rightOperand.convertToBool();
-  }
-
-  @override
-  NumState minus(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return _unknownNum(rightOperand);
-  }
-
-  @override
-  NumState negated() => NumState.UNKNOWN_VALUE;
-
-  @override
-  NumState remainder(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return _unknownNum(rightOperand);
-  }
-
-  @override
-  IntState shiftLeft(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  IntState shiftRight(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  NumState times(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return _unknownNum(rightOperand);
-  }
-
-  /**
-   * Return an object representing an unknown numeric value whose type is based
-   * on the type of the [rightOperand].
-   */
-  NumState _unknownNum(InstanceState rightOperand) {
-    if (rightOperand is IntState) {
-      return IntState.UNKNOWN_VALUE;
-    } else if (rightOperand is DoubleState) {
-      return DoubleState.UNKNOWN_VALUE;
-    }
-    return NumState.UNKNOWN_VALUE;
-  }
-}
-
-/**
- * A run-time exception that would be thrown during the evaluation of Dart code.
- */
-class EvaluationException extends JavaException {
-  /**
-   * The error code associated with the exception.
-   */
-  final ErrorCode errorCode;
-
-  /**
-   * Initialize a newly created exception to have the given [errorCode].
-   */
-  EvaluationException(this.errorCode);
-}
-
-/**
- * The result of attempting to evaluate an expression.
- */
-class EvaluationResult {
-  /**
-   * The value of the expression.
-   */
-  final DartObject value;
-
-  /**
-   * The errors that should be reported for the expression(s) that were
-   * evaluated.
-   */
-  final List<AnalysisError> _errors;
-
-  /**
-   * Initialize a newly created result object with the given [value] and set of
-   * [_errors]. Clients should use one of the factory methods: [forErrors] and
-   * [forValue].
-   */
-  EvaluationResult(this.value, this._errors);
-
-  /**
-   * Return a list containing the errors that should be reported for the
-   * expression(s) that were evaluated. If there are no such errors, the list
-   * will be empty. The list can be empty even if the expression is not a valid
-   * compile time constant if the errors would have been reported by other parts
-   * of the analysis engine.
-   */
-  List<AnalysisError> get errors =>
-      _errors == null ? AnalysisError.NO_ERRORS : _errors;
-
-  /**
-   * Return `true` if the expression is a compile-time constant expression that
-   * would not throw an exception when evaluated.
-   */
-  bool get isValid => _errors == null;
-
-  /**
-   * Return an evaluation result representing the result of evaluating an
-   * expression that is not a compile-time constant because of the given
-   * [errors].
-   */
-  static EvaluationResult forErrors(List<AnalysisError> errors) =>
-      new EvaluationResult(null, errors);
-
-  /**
-   * Return an evaluation result representing the result of evaluating an
-   * expression that is a compile-time constant that evaluates to the given
-   * [value].
-   */
-  static EvaluationResult forValue(DartObject value) =>
-      new EvaluationResult(value, null);
-}
-
-/**
- * The result of attempting to evaluate a expression.
- */
-class EvaluationResultImpl {
-  /**
-   * The errors encountered while trying to evaluate the compile time constant.
-   * These errors may or may not have prevented the expression from being a
-   * valid compile time constant.
-   */
-  List<AnalysisError> _errors;
-
-  /**
-   * The value of the expression, or `null` if the value couldn't be computed
-   * due to errors.
-   */
-  final DartObjectImpl value;
-
-  EvaluationResultImpl(this.value, [List<AnalysisError> errors]) {
-    this._errors = errors == null ? <AnalysisError>[] : errors;
-  }
-
-  List<AnalysisError> get errors => _errors;
-
-  bool equalValues(TypeProvider typeProvider, EvaluationResultImpl result) {
-    if (this.value != null) {
-      if (result.value == null) {
-        return false;
-      }
-      return value == result.value;
-    } else {
-      return false;
-    }
-  }
-
-  @override
-  String toString() {
-    if (value == null) {
-      return "error";
-    }
-    return value.toString();
-  }
-}
-
-/**
- * The state of an object representing a function.
- */
-class FunctionState extends InstanceState {
-  /**
-   * The element representing the function being modeled.
-   */
-  final ExecutableElement _element;
-
-  /**
-   * Initialize a newly created state to represent the function with the given
-   * [element].
-   */
-  FunctionState(this._element);
-
-  @override
-  int get hashCode => _element == null ? 0 : _element.hashCode;
-
-  @override
-  String get typeName => "Function";
-
-  @override
-  bool operator ==(Object object) =>
-      object is FunctionState && (_element == object._element);
-
-  @override
-  StringState convertToString() {
-    if (_element == null) {
-      return StringState.UNKNOWN_VALUE;
-    }
-    return new StringState(_element.name);
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (_element == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is FunctionState) {
-      ExecutableElement rightElement = rightOperand._element;
-      if (rightElement == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(_element == rightElement);
-    } else if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.FALSE_STATE;
-  }
-
-  @override
-  String toString() => _element == null ? "-unknown-" : _element.name;
-}
-
-/**
- * The state of an object representing a Dart object for which there is no more
- * specific state.
- */
-class GenericState extends InstanceState {
-  /**
-   * Pseudo-field that we use to represent fields in the superclass.
-   */
-  static String SUPERCLASS_FIELD = "(super)";
-
-  /**
-   * A state that can be used to represent an object whose state is not known.
-   */
-  static GenericState UNKNOWN_VALUE =
-      new GenericState(new HashMap<String, DartObjectImpl>());
-
-  /**
-   * The values of the fields of this instance.
-   */
-  final HashMap<String, DartObjectImpl> _fieldMap;
-
-  /**
-   * Initialize a newly created state to represent a newly created object. The
-   * [fieldMap] contains the values of the fields of the instance.
-   */
-  GenericState(this._fieldMap);
-
-  @override
-  HashMap<String, DartObjectImpl> get fields => _fieldMap;
-
-  @override
-  int get hashCode {
-    int hashCode = 0;
-    for (DartObjectImpl value in _fieldMap.values) {
-      hashCode += value.hashCode;
-    }
-    return hashCode;
-  }
-
-  @override
-  bool get isUnknown => identical(this, UNKNOWN_VALUE);
-
-  @override
-  String get typeName => "user defined type";
-
-  @override
-  bool operator ==(Object object) {
-    if (object is! GenericState) {
-      return false;
-    }
-    GenericState state = object as GenericState;
-    HashSet<String> otherFields =
-        new HashSet<String>.from(state._fieldMap.keys.toSet());
-    for (String fieldName in _fieldMap.keys.toSet()) {
-      if (_fieldMap[fieldName] != state._fieldMap[fieldName]) {
-        return false;
-      }
-      otherFields.remove(fieldName);
-    }
-    for (String fieldName in otherFields) {
-      if (state._fieldMap[fieldName] != _fieldMap[fieldName]) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  @override
-  StringState convertToString() => StringState.UNKNOWN_VALUE;
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.from(this == rightOperand);
-  }
-
-  @override
-  String toString() {
-    StringBuffer buffer = new StringBuffer();
-    List<String> fieldNames = _fieldMap.keys.toList();
-    fieldNames.sort();
-    bool first = true;
-    for (String fieldName in fieldNames) {
-      if (first) {
-        first = false;
-      } else {
-        buffer.write('; ');
-      }
-      buffer.write(fieldName);
-      buffer.write(' = ');
-      buffer.write(_fieldMap[fieldName]);
-    }
-    return buffer.toString();
-  }
-}
-
-/**
- * The state of an object representing a Dart object.
- */
-abstract class InstanceState {
-  /**
-   * If this represents a generic dart object, return a map from its field names
-   * to their values. Otherwise return null.
-   */
-  HashMap<String, DartObjectImpl> get fields => null;
-
-  /**
-   * Return `true` if this object represents an object whose type is 'bool'.
-   */
-  bool get isBool => false;
-
-  /**
-   * Return `true` if this object represents an object whose type is either
-   * 'bool', 'num', 'String', or 'Null'.
-   */
-  bool get isBoolNumStringOrNull => false;
-
-  /**
-   * Return `true` if this object represents an unknown value.
-   */
-  bool get isUnknown => false;
-
-  /**
-   * Return the name of the type of this value.
-   */
-  String get typeName;
-
-  /**
-   * Return the result of invoking the '+' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  InstanceState add(InstanceState rightOperand) {
-    if (this is StringState && rightOperand is StringState) {
-      return concatenate(rightOperand);
-    }
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Throw an exception if the given [state] does not represent a boolean value.
-   */
-  void assertBool(InstanceState state) {
-    if (!(state is BoolState || state is DynamicState)) {
-      throw new EvaluationException(CompileTimeErrorCode.CONST_EVAL_TYPE_BOOL);
-    }
-  }
-
-  /**
-   * Throw an exception if the given [state] does not represent a boolean,
-   * numeric, string or null value.
-   */
-  void assertBoolNumStringOrNull(InstanceState state) {
-    if (!(state is BoolState ||
-        state is DoubleState ||
-        state is IntState ||
-        state is NumState ||
-        state is StringState ||
-        state is NullState ||
-        state is DynamicState)) {
-      throw new EvaluationException(
-          CompileTimeErrorCode.CONST_EVAL_TYPE_BOOL_NUM_STRING);
-    }
-  }
-
-  /**
-   * Throw an exception if the given [state] does not represent an integer or
-   * null value.
-   */
-  void assertIntOrNull(InstanceState state) {
-    if (!(state is IntState ||
-        state is NumState ||
-        state is NullState ||
-        state is DynamicState)) {
-      throw new EvaluationException(CompileTimeErrorCode.CONST_EVAL_TYPE_INT);
-    }
-  }
-
-  /**
-   * Throw an exception if the given [state] does not represent a boolean,
-   * numeric, string or null value.
-   */
-  void assertNumOrNull(InstanceState state) {
-    if (!(state is DoubleState ||
-        state is IntState ||
-        state is NumState ||
-        state is NullState ||
-        state is DynamicState)) {
-      throw new EvaluationException(CompileTimeErrorCode.CONST_EVAL_TYPE_NUM);
-    }
-  }
-
-  /**
-   * Throw an exception if the given [state] does not represent a String value.
-   */
-  void assertString(InstanceState state) {
-    if (!(state is StringState || state is DynamicState)) {
-      throw new EvaluationException(CompileTimeErrorCode.CONST_EVAL_TYPE_BOOL);
-    }
-  }
-
-  /**
-   * Return the result of invoking the '&' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState bitAnd(InstanceState rightOperand) {
-    assertIntOrNull(this);
-    assertIntOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '~' operator on this object.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState bitNot() {
-    assertIntOrNull(this);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '|' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState bitOr(InstanceState rightOperand) {
-    assertIntOrNull(this);
-    assertIntOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '^' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState bitXor(InstanceState rightOperand) {
-    assertIntOrNull(this);
-    assertIntOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the ' ' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  StringState concatenate(InstanceState rightOperand) {
-    assertString(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of applying boolean conversion to this object.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState convertToBool() => BoolState.FALSE_STATE;
-
-  /**
-   * Return the result of converting this object to a String.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  StringState convertToString();
-
-  /**
-   * Return the result of invoking the '/' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  NumState divide(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '==' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState equalEqual(InstanceState rightOperand);
-
-  /**
-   * Return the result of invoking the '&gt;' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState greaterThan(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '&gt;=' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState greaterThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '~/' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState integerDivide(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the identical function on this object with
-   * the [rightOperand].
-   */
-  BoolState isIdentical(InstanceState rightOperand);
-
-  /**
-   * Return the result of invoking the '&lt;' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState lessThan(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '&lt;=' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState lessThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '&&' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState logicalAnd(InstanceState rightOperand) {
-    assertBool(this);
-    assertBool(rightOperand);
-    return BoolState.FALSE_STATE;
-  }
-
-  /**
-   * Return the result of invoking the '!' operator on this object.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState logicalNot() {
-    assertBool(this);
-    return BoolState.TRUE_STATE;
-  }
-
-  /**
-   * Return the result of invoking the '||' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  BoolState logicalOr(InstanceState rightOperand) {
-    assertBool(this);
-    assertBool(rightOperand);
-    return rightOperand.convertToBool();
-  }
-
-  /**
-   * Return the result of invoking the '-' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  NumState minus(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '-' operator on this object.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  NumState negated() {
-    assertNumOrNull(this);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '%' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  NumState remainder(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '&lt;&lt;' operator on this object with
-   * the [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState shiftLeft(InstanceState rightOperand) {
-    assertIntOrNull(this);
-    assertIntOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '&gt;&gt;' operator on this object with
-   * the [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState shiftRight(InstanceState rightOperand) {
-    assertIntOrNull(this);
-    assertIntOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the 'length' getter on this object.
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  IntState stringLength() {
-    assertString(this);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-
-  /**
-   * Return the result of invoking the '*' operator on this object with the
-   * [rightOperand].
-   *
-   * Throws an [EvaluationException] if the operator is not appropriate for an
-   * object of this kind.
-   */
-  NumState times(InstanceState rightOperand) {
-    assertNumOrNull(this);
-    assertNumOrNull(rightOperand);
-    throw new EvaluationException(CompileTimeErrorCode.INVALID_CONSTANT);
-  }
-}
-
-/**
- * The state of an object representing an int.
- */
-class IntState extends NumState {
-  /**
-   * A state that can be used to represent an int whose value is not known.
-   */
-  static IntState UNKNOWN_VALUE = new IntState(null);
-
-  /**
-   * The value of this instance.
-   */
-  final int value;
-
-  /**
-   * Initialize a newly created state to represent an int with the given
-   * [value].
-   */
-  IntState(this.value);
-
-  @override
-  int get hashCode => value == null ? 0 : value.hashCode;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  bool get isUnknown => value == null;
-
-  @override
-  String get typeName => "int";
-
-  @override
-  bool operator ==(Object object) =>
-      object is IntState && (value == object.value);
-
-  @override
-  NumState add(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      if (rightOperand is DoubleState) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value + rightValue);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return new DoubleState(value.toDouble() + rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState bitAnd(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value & rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState bitNot() {
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    return new IntState(~value);
-  }
-
-  @override
-  IntState bitOr(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value | rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState bitXor(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value ^ rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  StringState convertToString() {
-    if (value == null) {
-      return StringState.UNKNOWN_VALUE;
-    }
-    return new StringState(value.toString());
-  }
-
-  @override
-  NumState divide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return DoubleState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return DoubleState.UNKNOWN_VALUE;
-      } else {
-        return new DoubleState(value.toDouble() / rightValue.toDouble());
-      }
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return new DoubleState(value.toDouble() / rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return DoubleState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState greaterThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.compareTo(rightValue) > 0);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.toDouble() > rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState greaterThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.compareTo(rightValue) >= 0);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.toDouble() >= rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState integerDivide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      } else if (rightValue == 0) {
-        throw new EvaluationException(
-            CompileTimeErrorCode.CONST_EVAL_THROWS_IDBZE);
-      }
-      return new IntState(value ~/ rightValue);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      double result = value.toDouble() / rightValue;
-      return new IntState(result.toInt());
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value == rightValue);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(rightValue == value.toDouble());
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.FALSE_STATE;
-  }
-
-  @override
-  BoolState lessThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.compareTo(rightValue) < 0);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.toDouble() < rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  BoolState lessThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.compareTo(rightValue) <= 0);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value.toDouble() <= rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  NumState minus(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      if (rightOperand is DoubleState) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value - rightValue);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return new DoubleState(value.toDouble() - rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  NumState negated() {
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    return new IntState(-value);
-  }
-
-  @override
-  NumState remainder(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      if (rightOperand is DoubleState) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      } else if (rightValue == 0) {
-        return new DoubleState(value.toDouble() % rightValue.toDouble());
-      }
-      return new IntState(value.remainder(rightValue));
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return new DoubleState(value.toDouble() % rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState shiftLeft(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      } else if (rightValue.bitLength > 31) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value << rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  IntState shiftRight(InstanceState rightOperand) {
-    assertIntOrNull(rightOperand);
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      } else if (rightValue.bitLength > 31) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value >> rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  NumState times(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (value == null) {
-      if (rightOperand is DoubleState) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new IntState(value * rightValue);
-    } else if (rightOperand is DoubleState) {
-      double rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return DoubleState.UNKNOWN_VALUE;
-      }
-      return new DoubleState(value.toDouble() * rightValue);
-    } else if (rightOperand is DynamicState || rightOperand is NumState) {
-      return UNKNOWN_VALUE;
-    }
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  String toString() => value == null ? "-unknown-" : value.toString();
-}
-
-/**
- * The state of an object representing a list.
- */
-class ListState extends InstanceState {
-  /**
-   * The elements of the list.
-   */
-  final List<DartObjectImpl> _elements;
-
-  /**
-   * Initialize a newly created state to represent a list with the given
-   * [elements].
-   */
-  ListState(this._elements);
-
-  @override
-  int get hashCode {
-    int value = 0;
-    int count = _elements.length;
-    for (int i = 0; i < count; i++) {
-      value = (value << 3) ^ _elements[i].hashCode;
-    }
-    return value;
-  }
-
-  @override
-  String get typeName => "List";
-
-  @override
-  bool operator ==(Object object) {
-    if (object is! ListState) {
-      return false;
-    }
-    List<DartObjectImpl> otherElements = (object as ListState)._elements;
-    int count = _elements.length;
-    if (otherElements.length != count) {
-      return false;
-    } else if (count == 0) {
-      return true;
-    }
-    for (int i = 0; i < count; i++) {
-      if (_elements[i] != otherElements[i]) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  @override
-  StringState convertToString() => StringState.UNKNOWN_VALUE;
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.from(this == rightOperand);
-  }
-
-  @override
-  String toString() {
-    StringBuffer buffer = new StringBuffer();
-    buffer.write('[');
-    bool first = true;
-    _elements.forEach((DartObjectImpl element) {
-      if (first) {
-        first = false;
-      } else {
-        buffer.write(', ');
-      }
-      buffer.write(element);
-    });
-    buffer.write(']');
-    return buffer.toString();
-  }
-}
-
-/**
- * The state of an object representing a map.
- */
-class MapState extends InstanceState {
-  /**
-   * The entries in the map.
-   */
-  final HashMap<DartObjectImpl, DartObjectImpl> _entries;
-
-  /**
-   * Initialize a newly created state to represent a map with the given
-   * [entries].
-   */
-  MapState(this._entries);
-
-  @override
-  int get hashCode {
-    int value = 0;
-    for (DartObjectImpl key in _entries.keys.toSet()) {
-      value = (value << 3) ^ key.hashCode;
-    }
-    return value;
-  }
-
-  @override
-  String get typeName => "Map";
-
-  @override
-  bool operator ==(Object object) {
-    if (object is! MapState) {
-      return false;
-    }
-    HashMap<DartObjectImpl, DartObjectImpl> otherElements =
-        (object as MapState)._entries;
-    int count = _entries.length;
-    if (otherElements.length != count) {
-      return false;
-    } else if (count == 0) {
-      return true;
-    }
-    for (DartObjectImpl key in _entries.keys) {
-      DartObjectImpl value = _entries[key];
-      DartObjectImpl otherValue = otherElements[key];
-      if (value != otherValue) {
-        return false;
-      }
-    }
-    return true;
-  }
-
-  @override
-  StringState convertToString() => StringState.UNKNOWN_VALUE;
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.from(this == rightOperand);
-  }
-
-  @override
-  String toString() {
-    StringBuffer buffer = new StringBuffer();
-    buffer.write('{');
-    bool first = true;
-    _entries.forEach((DartObjectImpl key, DartObjectImpl value) {
-      if (first) {
-        first = false;
-      } else {
-        buffer.write(', ');
-      }
-      buffer.write(key);
-      buffer.write(' = ');
-      buffer.write(value);
-    });
-    buffer.write('}');
-    return buffer.toString();
-  }
-}
-
-/**
- * The state of an object representing the value 'null'.
- */
-class NullState extends InstanceState {
-  /**
-   * An instance representing the boolean value 'null'.
-   */
-  static NullState NULL_STATE = new NullState();
-
-  @override
-  int get hashCode => 0;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  String get typeName => "Null";
-
-  @override
-  bool operator ==(Object object) => object is NullState;
-
-  @override
-  BoolState convertToBool() {
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  StringState convertToString() => new StringState("null");
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.from(rightOperand is NullState);
-  }
-
-  @override
-  BoolState logicalNot() {
-    throw new EvaluationException(
-        CompileTimeErrorCode.CONST_EVAL_THROWS_EXCEPTION);
-  }
-
-  @override
-  String toString() => "null";
-}
-
-/**
- * The state of an object representing a number of an unknown type (a 'num').
- */
-class NumState extends InstanceState {
-  /**
-   * A state that can be used to represent a number whose value is not known.
-   */
-  static NumState UNKNOWN_VALUE = new NumState();
-
-  @override
-  int get hashCode => 7;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  bool get isUnknown => identical(this, UNKNOWN_VALUE);
-
-  @override
-  String get typeName => "num";
-
-  @override
-  bool operator ==(Object object) => object is NumState;
-
-  @override
-  NumState add(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return UNKNOWN_VALUE;
-  }
-
-  @override
-  StringState convertToString() => StringState.UNKNOWN_VALUE;
-
-  @override
-  NumState divide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return DoubleState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState greaterThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState greaterThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  IntState integerDivide(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    if (rightOperand is IntState) {
-      int rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return IntState.UNKNOWN_VALUE;
-      } else if (rightValue == 0) {
-        throw new EvaluationException(
-            CompileTimeErrorCode.CONST_EVAL_THROWS_IDBZE);
-      }
-    } else if (rightOperand is DynamicState) {
-      return IntState.UNKNOWN_VALUE;
-    }
-    return IntState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState lessThan(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  BoolState lessThanOrEqual(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return BoolState.UNKNOWN_VALUE;
-  }
-
-  @override
-  NumState minus(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return UNKNOWN_VALUE;
-  }
-
-  @override
-  NumState negated() => UNKNOWN_VALUE;
-
-  @override
-  NumState remainder(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return UNKNOWN_VALUE;
-  }
-
-  @override
-  NumState times(InstanceState rightOperand) {
-    assertNumOrNull(rightOperand);
-    return UNKNOWN_VALUE;
-  }
-
-  @override
-  String toString() => "-unknown-";
-}
-
-/**
- * An object used to add reference information for a given variable to the
- * bi-directional mapping used to order the evaluation of constants.
- */
-class ReferenceFinder extends RecursiveAstVisitor<Object> {
-  /**
-   * The callback which should be used to report any dependencies that were
-   * found.
-   */
-  final ReferenceFinderCallback _callback;
-
-  /**
-   * Initialize a newly created reference finder to find references from a given
-   * variable to other variables and to add those references to the given graph.
-   * The [_callback] will be invoked for every dependency found.
-   */
-  ReferenceFinder(this._callback);
-
-  @override
-  Object visitInstanceCreationExpression(InstanceCreationExpression node) {
-    if (node.isConst) {
-      ConstructorElement constructor = _getConstructorImpl(node.staticElement);
-      if (constructor != null) {
-        _callback(constructor);
-      }
-    }
-    return super.visitInstanceCreationExpression(node);
-  }
-
-  @override
-  Object visitLabel(Label node) {
-    // We are visiting the "label" part of a named expression in a function
-    // call (presumably a constructor call), e.g. "const C(label: ...)".  We
-    // don't want to visit the SimpleIdentifier for the label because that's a
-    // reference to a function parameter that needs to be filled in; it's not a
-    // constant whose value we depend on.
-    return null;
-  }
-
-  @override
-  Object visitRedirectingConstructorInvocation(
-      RedirectingConstructorInvocation node) {
-    super.visitRedirectingConstructorInvocation(node);
-    ConstructorElement target = _getConstructorImpl(node.staticElement);
-    if (target != null) {
-      _callback(target);
-    }
-    return null;
-  }
-
-  @override
-  Object visitSimpleIdentifier(SimpleIdentifier node) {
-    Element element = node.staticElement;
-    if (element is PropertyAccessorElement) {
-      element = (element as PropertyAccessorElement).variable;
-    }
-    if (element is VariableElement && element.isConst) {
-      _callback(element);
-    }
-    return null;
-  }
-
-  @override
-  Object visitSuperConstructorInvocation(SuperConstructorInvocation node) {
-    super.visitSuperConstructorInvocation(node);
-    ConstructorElement constructor = _getConstructorImpl(node.staticElement);
-    if (constructor != null) {
-      _callback(constructor);
-    }
-    return null;
-  }
-}
-
-/**
- * The state of an object representing a string.
- */
-class StringState extends InstanceState {
-  /**
-   * A state that can be used to represent a double whose value is not known.
-   */
-  static StringState UNKNOWN_VALUE = new StringState(null);
-
-  /**
-   * The value of this instance.
-   */
-  final String value;
-
-  /**
-   * Initialize a newly created state to represent the given [value].
-   */
-  StringState(this.value);
-
-  @override
-  int get hashCode => value == null ? 0 : value.hashCode;
-
-  @override
-  bool get isBoolNumStringOrNull => true;
-
-  @override
-  bool get isUnknown => value == null;
-
-  @override
-  String get typeName => "String";
-
-  @override
-  bool operator ==(Object object) =>
-      object is StringState && (value == object.value);
-
-  @override
-  StringState concatenate(InstanceState rightOperand) {
-    if (value == null) {
-      return UNKNOWN_VALUE;
-    }
-    if (rightOperand is StringState) {
-      String rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return UNKNOWN_VALUE;
-      }
-      return new StringState("$value$rightValue");
-    } else if (rightOperand is DynamicState) {
-      return UNKNOWN_VALUE;
-    }
-    return super.concatenate(rightOperand);
-  }
-
-  @override
-  StringState convertToString() => this;
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is StringState) {
-      String rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value == rightValue);
-    } else if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.FALSE_STATE;
-  }
-
-  @override
-  IntState stringLength() {
-    if (value == null) {
-      return IntState.UNKNOWN_VALUE;
-    }
-    return new IntState(value.length);
-  }
-
-  @override
-  String toString() => value == null ? "-unknown-" : "'$value'";
-}
-
-/**
- * The state of an object representing a symbol.
- */
-class SymbolState extends InstanceState {
-  /**
-   * The value of this instance.
-   */
-  final String value;
-
-  /**
-   * Initialize a newly created state to represent the given [value].
-   */
-  SymbolState(this.value);
-
-  @override
-  int get hashCode => value == null ? 0 : value.hashCode;
-
-  @override
-  String get typeName => "Symbol";
-
-  @override
-  bool operator ==(Object object) =>
-      object is SymbolState && (value == object.value);
-
-  @override
-  StringState convertToString() {
-    if (value == null) {
-      return StringState.UNKNOWN_VALUE;
-    }
-    return new StringState(value);
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (value == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is SymbolState) {
-      String rightValue = rightOperand.value;
-      if (rightValue == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(value == rightValue);
-    } else if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.FALSE_STATE;
-  }
-
-  @override
-  String toString() => value == null ? "-unknown-" : "#$value";
-}
-
-/**
- * The state of an object representing a type.
- */
-class TypeState extends InstanceState {
-  /**
-   * The element representing the type being modeled.
-   */
-  final Element _element;
-
-  /**
-   * Initialize a newly created state to represent the given [value].
-   */
-  TypeState(this._element);
-
-  @override
-  int get hashCode => _element == null ? 0 : _element.hashCode;
-
-  @override
-  String get typeName => "Type";
-
-  @override
-  bool operator ==(Object object) =>
-      object is TypeState && (_element == object._element);
-
-  @override
-  StringState convertToString() {
-    if (_element == null) {
-      return StringState.UNKNOWN_VALUE;
-    }
-    return new StringState(_element.name);
-  }
-
-  @override
-  BoolState equalEqual(InstanceState rightOperand) {
-    assertBoolNumStringOrNull(rightOperand);
-    return isIdentical(rightOperand);
-  }
-
-  @override
-  BoolState isIdentical(InstanceState rightOperand) {
-    if (_element == null) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    if (rightOperand is TypeState) {
-      Element rightElement = rightOperand._element;
-      if (rightElement == null) {
-        return BoolState.UNKNOWN_VALUE;
-      }
-      return BoolState.from(_element == rightElement);
-    } else if (rightOperand is DynamicState) {
-      return BoolState.UNKNOWN_VALUE;
-    }
-    return BoolState.FALSE_STATE;
-  }
-
-  @override
-  String toString() => _element == null ? "-unknown-" : _element.name;
-}