Stop running pub get at gclient sync time and fix build bugs

mojo/public/dart/third_party/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 engine.constant;
+
+import 'dart:collection';
+
+import 'package:analyzer/src/generated/engine.dart';
+import 'package:analyzer/src/generated/utilities_general.dart';
+import 'package:analyzer/src/task/dart.dart';
+
+import 'ast.dart';
+import 'element.dart';
+import 'engine.dart' show AnalysisEngine, RecordingErrorListener;
+import 'error.dart';
+import 'java_core.dart';
+import 'resolver.dart' show TypeProvider, TypeSystem, TypeSystemImpl;
+import 'scanner.dart' show Token, TokenType;
+import 'source.dart' show Source;
+import 'utilities_collection.dart';
+import 'utilities_dart.dart' show ParameterKind;
+
+/**
+ * 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
+  bool get hasExactValue => true;
+
+  @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
+  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;
+  }
+}
+
+/**
+ * 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 system.  This is used to gues 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(TypeProvider typeProvider, this._declaredVariables,
+      {ConstantEvaluationValidator validator})
+      : validator = validator != null
+          ? validator
+          : new ConstantEvaluationValidator_ForProduction(),
+        typeSystem = new TypeSystemImpl(typeProvider);
+
+  /**
+   * The type provider used to access the known types.
+   */
+  TypeProvider get typeProvider => typeSystem.typeProvider;
+
+  /**
+   * 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].stringValue;
+    return isValidPublicSymbol(name);
+  }
+
+  /**
+   * Compute the constant value associated with the given [constant].
+   */
+  void computeConstantValue(ConstantEvaluationTarget constant) {
+    validator.beforeComputeValue(constant);
+    if (constant is ParameterElement) {
+      if (constant.initializer != null) {
+        Expression defaultValue =
+            (constant as PotentiallyConstVariableElement).constantInitializer;
+        if (defaultValue != null) {
+          RecordingErrorListener errorListener = new RecordingErrorListener();
+          ErrorReporter errorReporter =
+              new ErrorReporter(errorListener, constant.source);
+          DartObjectImpl dartObject =
+              defaultValue.accept(new ConstantVisitor(this, errorReporter));
+          (constant as ParameterElementImpl).evaluationResult =
+              new EvaluationResultImpl(dartObject, errorListener.errors);
+        }
+      }
+    } else if (constant is VariableElement) {
+      Expression constantInitializer =
+          (constant as PotentiallyConstVariableElement).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 as VariableElementImpl).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 ConstantEvaluationTarget_Annotation) {
+      Annotation constNode = constant.annotation;
+      ElementAnnotationImpl elementAnnotation = constNode.elementAnnotation;
+      // elementAnnotation is null if the annotation couldn't be resolved, in
+      // which case we skip it.
+      if (elementAnnotation != null) {
+        Element element = elementAnnotation.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) {
+            elementAnnotation.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.
+            elementAnnotation.evaluationResult = new EvaluationResultImpl(null);
+          }
+        } else if (element is ConstructorElementImpl &&
+            element.isConst &&
+            constNode.arguments != null) {
+          RecordingErrorListener errorListener = new RecordingErrorListener();
+          CompilationUnit sourceCompilationUnit =
+              constNode.getAncestor((node) => node is CompilationUnit);
+          ErrorReporter errorReporter = new ErrorReporter(
+              errorListener, sourceCompilationUnit.element.source);
+          ConstantVisitor constantVisitor =
+              new ConstantVisitor(this, errorReporter);
+          DartObjectImpl result = evaluateConstructorCall(constNode,
+              constNode.arguments.arguments, element, constantVisitor,
+              errorReporter);
+          elementAnnotation.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.
+          elementAnnotation.evaluationResult = new EvaluationResultImpl(null);
+        }
+      }
+    } 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].
+   *
+   * Note that it's possible (in erroneous code) for a constant to depend on a
+   * non-constant.  When this happens, we report the dependency anyhow so that
+   * if the non-constant changes to a constant, we will know to recompute the
+   * thing that depends on it.  [computeDependencies] and
+   * [computeConstantValue] are responsible for ignoring the request if they
+   * are asked to act on a non-constant target.
+   */
+  void computeDependencies(
+      ConstantEvaluationTarget constant, ReferenceFinderCallback callback) {
+    ReferenceFinder referenceFinder = new ReferenceFinder(callback);
+    if (constant is ParameterElement) {
+      if (constant.initializer != null) {
+        Expression defaultValue =
+            (constant as ConstVariableElement).constantInitializer;
+        if (defaultValue != null) {
+          defaultValue.accept(referenceFinder);
+        }
+      }
+    } else if (constant is PotentiallyConstVariableElement) {
+      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 =
+              ConstantEvaluationEngine
+                  ._getConstructorBase(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 = ConstantEvaluationEngine
+                ._getConstructorBase(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 ConstantEvaluationTarget_Annotation) {
+      Annotation constNode = constant.annotation;
+      ElementAnnotationImpl elementAnnotation = constNode.elementAnnotation;
+      // elementAnnotation is null if the annotation couldn't be resolved, in
+      // which case we skip it.
+      if (elementAnnotation != null) {
+        Element element = elementAnnotation.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 {
+      // 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 (!_getConstructorBase(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].stringValue;
+        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].stringValue;
+        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 = _getConstructorBase(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;
+        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] = evaluationResult.value;
+      }
+    }
+    // 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 = _getConstructorBase(constructor);
+        constructorsVisited.add(constructorBase);
+        ConstructorElement redirectedConstructorBase =
+            _getConstructorBase(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();
+
+  static ConstructorElementImpl _getConstructorBase(
+      ConstructorElement constructor) {
+    while (constructor is ConstructorMember) {
+      constructor = (constructor as ConstructorMember).baseElement;
+    }
+    return constructor;
+  }
+}
+
+/**
+ * Wrapper around an [Annotation] which can be used as a
+ * [ConstantEvaluationTarget].
+ */
+class ConstantEvaluationTarget_Annotation implements ConstantEvaluationTarget {
+  final AnalysisContext context;
+  final Source source;
+  final Source librarySource;
+  final Annotation annotation;
+
+  ConstantEvaluationTarget_Annotation(
+      this.context, this.source, this.librarySource, this.annotation);
+
+  @override
+  int get hashCode => JenkinsSmiHash.hash3(
+      source.hashCode, librarySource.hashCode, annotation.hashCode);
+
+  @override
+  bool operator ==(other) {
+    if (other is ConstantEvaluationTarget_Annotation) {
+      return this.context == other.context &&
+          this.source == other.source &&
+          this.librarySource == other.librarySource &&
+          this.annotation == other.annotation;
+    } else {
+      return false;
+    }
+  }
+}
+
+/**
+ * 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) {}
+}
+
+/**
+ * Instances of the class `ConstantEvaluator` 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 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;
+
+  /**
+   * Initialize a newly created evaluator to evaluate expressions in the given
+   * [source]. The [typeProvider] is the type provider used to access known
+   * types.
+   */
+  ConstantEvaluator(this._source, this._typeProvider);
+
+  EvaluationResult evaluate(Expression expression) {
+    RecordingErrorListener errorListener = new RecordingErrorListener();
+    ErrorReporter errorReporter = new ErrorReporter(errorListener, _source);
+    DartObjectImpl result = expression.accept(new ConstantVisitor(
+        new ConstantEvaluationEngine(_typeProvider, new DeclaredVariables()),
+        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 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.
+   */
+  HashSet<ConstantEvaluationTarget> constantsToCompute =
+      new HashSet<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);
+    constantsToCompute.add(new ConstantEvaluationTarget_Annotation(
+        context, source, librarySource, node));
+    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 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 (node.element != null) {
+        constantsToCompute.add(node.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])
+      : evaluationEngine = new ConstantEvaluationEngine(
+          typeProvider, declaredVariables, validator: validator);
+
+  /**
+   * 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) {
+      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 {
+        // 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.isTrue) {
+      return thenResult;
+    } else if (conditionResult.isFalse) {
+      return elseResult;
+    }
+    ParameterizedType thenType = thenResult.type;
+    ParameterizedType elseType = elseResult.type;
+    return new DartObjectImpl.validWithUnknownValue(
+        _typeSystem.getLeastUpperBound(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.substitute4([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;
+    HashMap<DartObjectImpl, DartObjectImpl> map =
+        new HashMap<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.substitute4([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;
+  }
+}
+
+/**
+ * The state of a Dart object.
+ */
+abstract class DartObject {
+  /**
+   * Return the boolean value of this object, or `null` if either the value of
+   * this object is not known or this object is not of type 'bool'.
+   */
+  bool get boolValue;
+
+  /**
+   * Return the floating point value of this object, or `null` if either the
+   * value of this object is not known or this object is not of type 'double'.
+   */
+  double get doubleValue;
+
+  /**
+   * Return `true` if this object's value can be represented exactly.
+   */
+  bool get hasExactValue;
+
+  /**
+   * Return the integer value of this object, or `null` if either the value of
+   * this object is not known or this object is not of type 'int'.
+   */
+  int get intValue;
+
+  /**
+   * Return `true` if this object represents the value 'false'.
+   */
+  bool get isFalse;
+
+  /**
+   * Return `true` if this object represents the value 'null'.
+   */
+  bool get isNull;
+
+  /**
+   * Return `true` if this object represents the value 'true'.
+   */
+  bool get isTrue;
+
+  /**
+   * Return the string value of this object, or `null` if either the value of
+   * this object is not known or this object is not of type 'String'.
+   */
+  String get stringValue;
+
+  /**
+   * Return the run-time type of this object.
+   */
+  ParameterizedType get type;
+
+  /**
+   * Return this object's value if it can be represented exactly, or `null` if
+   * either the value cannot be represented exactly or if the value is `null`.
+   * Clients should use [hasExactValue] to distinguish between these two cases.
+   */
+  Object get value;
+}
+
+/**
+ * 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 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.
+   */
+  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);
+  }
+
+  @override
+  bool get boolValue {
+    if (_state is BoolState) {
+      return (_state as BoolState).value;
+    }
+    return null;
+  }
+
+  @override
+  double get doubleValue {
+    if (_state is DoubleState) {
+      return (_state as DoubleState).value;
+    }
+    return null;
+  }
+
+  HashMap<String, DartObjectImpl> get fields => _state.fields;
+
+  @override
+  bool get hasExactValue => _state.hasExactValue;
+
+  @override
+  int get hashCode => JenkinsSmiHash.hash2(type.hashCode, _state.hashCode);
+
+  @override
+  int get intValue {
+    if (_state is IntState) {
+      return (_state as IntState).value;
+    }
+    return null;
+  }
+
+  /**
+   * 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 isFalse =>
+      _state is BoolState && identical((_state as BoolState).value, false);
+
+  @override
+  bool get isNull => _state is NullState;
+
+  @override
+  bool get isTrue =>
+      _state is BoolState && identical((_state as BoolState).value, true);
+
+  /**
+   * 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
+  String get stringValue {
+    if (_state is StringState) {
+      return (_state as StringState).value;
+    }
+    return null;
+  }
+
+  @override
+  Object get value => _state.value;
+
+  @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));
+  }
+
+  /**
+   * 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 ${result.runtimeType}");
+  }
+
+  @override
+  String toString() => "${type.displayName} ($_state)";
+}
+
+/**
+ * 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
+  bool get hasExactValue => true;
+
+  @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;
+  }
+
+  @deprecated // Use new EvaluationResultImpl(value)
+  EvaluationResultImpl.con1(this.value) {
+    this._errors = new List<AnalysisError>(0);
+  }
+
+  @deprecated // Use new EvaluationResultImpl(value, errors)
+  EvaluationResultImpl.con2(this.value, List<AnalysisError> this._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's value can be represented exactly.
+   */
+  bool get hasExactValue => false;
+
+  /**
+   * 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 this object's value if it can be represented exactly, or `null` if
+   * either the value cannot be represented exactly or if the value is `null`.
+   * Clients should use [hasExactValue] to distinguish between these two cases.
+   */
+  Object get value => null;
+
+  /**
+   * 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
+  bool get hasExactValue => true;
+
+  @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
+  bool get hasExactValue {
+    int count = _elements.length;
+    for (int i = 0; i < count; i++) {
+      if (!_elements[i].hasExactValue) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  @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
+  List<Object> get value {
+    int count = _elements.length;
+    List<Object> result = new List<Object>(count);
+    for (int i = 0; i < count; i++) {
+      DartObjectImpl element = _elements[i];
+      if (!element.hasExactValue) {
+        return null;
+      }
+      result[i] = element.value;
+    }
+    return result;
+  }
+
+  @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
+  bool get hasExactValue {
+    for (DartObjectImpl key in _entries.keys) {
+      if (!key.hasExactValue || !_entries[key].hasExactValue) {
+        return false;
+      }
+    }
+    return true;
+  }
+
+  @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
+  Map<Object, Object> get value {
+    HashMap<Object, Object> result = new HashMap<Object, Object>();
+    for (DartObjectImpl key in _entries.keys) {
+      DartObjectImpl value = _entries[key];
+      if (!key.hasExactValue || !value.hasExactValue) {
+        return null;
+      }
+      result[key.value] = value.value;
+    }
+    return result;
+  }
+
+  @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
+  bool get hasExactValue => true;
+
+  @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 =
+          ConstantEvaluationEngine._getConstructorBase(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 =
+        ConstantEvaluationEngine._getConstructorBase(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) {
+      _callback(element);
+    }
+    return null;
+  }
+
+  @override
+  Object visitSuperConstructorInvocation(SuperConstructorInvocation node) {
+    super.visitSuperConstructorInvocation(node);
+    ConstructorElement constructor =
+        ConstantEvaluationEngine._getConstructorBase(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
+  bool get hasExactValue => true;
+
+  @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
+  bool get hasExactValue => true;
+
+  @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
+  Element get value => _element;
+
+  @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;
+}