pkg/analyzer/lib/src/generated/error_verifier.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.

import 'dart:collection';
import "dart:math" as math;

import 'package:analyzer/dart/ast/ast.dart';
import 'package:analyzer/dart/ast/standard_resolution_map.dart';
import 'package:analyzer/dart/ast/token.dart';
import 'package:analyzer/dart/ast/visitor.dart';
import 'package:analyzer/dart/element/element.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/dart/element/visitor.dart';
import 'package:analyzer/error/error.dart';
import 'package:analyzer/error/listener.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/constant/evaluation.dart';
import 'package:analyzer/src/dart/element/element.dart';
import 'package:analyzer/src/dart/element/inheritance_manager2.dart';
import 'package:analyzer/src/dart/element/member.dart';
import 'package:analyzer/src/dart/element/type.dart';
import 'package:analyzer/src/error/codes.dart';
import 'package:analyzer/src/error/literal_element_verifier.dart';
import 'package:analyzer/src/error/pending_error.dart';
import 'package:analyzer/src/generated/element_resolver.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:analyzer/src/generated/java_engine.dart';
import 'package:analyzer/src/generated/parser.dart' show ParserErrorCode;
import 'package:analyzer/src/generated/resolver.dart';
import 'package:analyzer/src/generated/sdk.dart' show DartSdk, SdkLibrary;
import 'package:analyzer/src/generated/source.dart';

/**
 * A visitor used to traverse an AST structure looking for additional errors and
 * warnings not covered by the parser and resolver.
 */
class ErrorVerifier extends RecursiveAstVisitor<void> {
  /**
   * The error reporter by which errors will be reported.
   */
  final ErrorReporter _errorReporter;

  /**
   * The current library that is being analyzed.
   */
  final LibraryElement _currentLibrary;

  /**
   * The type representing the type 'bool'.
   */
  InterfaceType _boolType;

  /**
   * The type representing the type 'int'.
   */
  InterfaceType _intType;

  /**
   * The options for verification.
   */
  AnalysisOptionsImpl _options;

  /**
   * The object providing access to the types defined by the language.
   */
  final TypeProvider _typeProvider;

  /**
   * The type system primitives
   */
  TypeSystem _typeSystem;

  /**
   * The manager for the inheritance mappings.
   */
  final InheritanceManager2 _inheritanceManager;

  /**
   * A flag indicating whether the visitor is currently within a constructor
   * declaration that is 'const'.
   *
   * See [visitConstructorDeclaration].
   */
  bool _isEnclosingConstructorConst = false;

  /**
   * A flag indicating whether we are currently within a function body marked as
   * being asynchronous.
   */
  bool _inAsync = false;

  /**
   * A flag indicating whether we are currently within a function body marked a
   *  being a generator.
   */
  bool _inGenerator = false;

  /**
   * A flag indicating whether the visitor is currently within a catch clause.
   *
   * See [visitCatchClause].
   */
  bool _isInCatchClause = false;

  /**
   * A flag indicating whether the visitor is currently within a comment.
   */
  bool _isInComment = false;

  /**
   * A flag indicating whether the visitor is currently within an instance
   * creation expression.
   */
  bool _isInConstInstanceCreation = false;

  /**
   * A flag indicating whether the visitor is currently within a native class
   * declaration.
   */
  bool _isInNativeClass = false;

  /**
   * A flag indicating whether the visitor is currently within a static variable
   * declaration.
   */
  bool _isInStaticVariableDeclaration = false;

  /**
   * A flag indicating whether the visitor is currently within an instance
   * variable declaration.
   */
  bool _isInInstanceVariableDeclaration = false;

  /**
   * A flag indicating whether the visitor is currently within an instance
   * variable initializer.
   */
  bool _isInInstanceVariableInitializer = false;

  /**
   * A flag indicating whether the visitor is currently within a constructor
   * initializer.
   */
  bool _isInConstructorInitializer = false;

  /**
   * This is set to `true` iff the visitor is currently within a function typed
   * formal parameter.
   */
  bool _isInFunctionTypedFormalParameter = false;

  /**
   * A flag indicating whether the visitor is currently within a static method.
   * By "method" here getter, setter and operator declarations are also implied
   * since they are all represented with a [MethodDeclaration] in the AST
   * structure.
   */
  bool _isInStaticMethod = false;

  /**
   * A flag indicating whether the visitor is currently within a factory
   * constructor.
   */
  bool _isInFactory = false;

  /**
   * A flag indicating whether the visitor is currently within code in the SDK.
   */
  bool _isInSystemLibrary = false;

  /**
   * A flag indicating whether the current library contains at least one import
   * directive with a URI that uses the "dart-ext" scheme.
   */
  bool _hasExtUri = false;

  /**
   * This is set to `false` on the entry of every [BlockFunctionBody], and is
   * restored to the enclosing value on exit. The value is used in
   * [_checkForMixedReturns] to prevent both
   * [StaticWarningCode.MIXED_RETURN_TYPES] and
   * [StaticWarningCode.RETURN_WITHOUT_VALUE] from being generated in the same
   * function body.
   */
  bool _hasReturnWithoutValue = false;

  /**
   * The class containing the AST nodes being visited, or `null` if we are not
   * in the scope of a class.
   */
  ClassElementImpl _enclosingClass;

  /**
   * The enum containing the AST nodes being visited, or `null` if we are not
   * in the scope of an enum.
   */
  ClassElement _enclosingEnum;

  /**
   * The method or function that we are currently visiting, or `null` if we are
   * not inside a method or function.
   */
  ExecutableElement _enclosingFunction;

  /**
   * The return statements found in the method or function that we are currently
   * visiting that have a return value.
   */
  List<ReturnStatement> _returnsWith = new List<ReturnStatement>();

  /**
   * The return statements found in the method or function that we are currently
   * visiting that do not have a return value.
   */
  List<ReturnStatement> _returnsWithout = new List<ReturnStatement>();

  /**
   * This map is initialized when visiting the contents of a class declaration.
   * If the visitor is not in an enclosing class declaration, then the map is
   * set to `null`.
   *
   * When set the map maps the set of [FieldElement]s in the class to an
   * [INIT_STATE.NOT_INIT] or [INIT_STATE.INIT_IN_DECLARATION]. The `checkFor*`
   * methods, specifically [_checkForAllFinalInitializedErrorCodes], can make a
   * copy of the map to compute error code states. The `checkFor*` methods
   * should only ever make a copy, or read from this map after it has been set
   * in [visitClassDeclaration].
   *
   * See [visitClassDeclaration], and [_checkForAllFinalInitializedErrorCodes].
   */
  Map<FieldElement, INIT_STATE> _initialFieldElementsMap;

  /**
   * A table mapping name of the library to the export directive which export
   * this library.
   */
  Map<String, LibraryElement> _nameToExportElement =
      new HashMap<String, LibraryElement>();

  /**
   * A table mapping name of the library to the import directive which import
   * this library.
   */
  Map<String, LibraryElement> _nameToImportElement =
      new HashMap<String, LibraryElement>();

  /**
   * A table mapping names to the exported elements.
   */
  Map<String, Element> _exportedElements = new HashMap<String, Element>();

  /**
   * A set of the names of the variable initializers we are visiting now.
   */
  HashSet<String> _namesForReferenceToDeclaredVariableInInitializer =
      new HashSet<String>();

  /**
   * The elements that will be defined later in the current scope, but right
   * now are not declared.
   */
  HiddenElements _hiddenElements = null;

  /**
   * A list of types used by the [CompileTimeErrorCode.EXTENDS_DISALLOWED_CLASS]
   * and [CompileTimeErrorCode.IMPLEMENTS_DISALLOWED_CLASS] error codes.
   */
  List<InterfaceType> _DISALLOWED_TYPES_TO_EXTEND_OR_IMPLEMENT;

  final _UninstantiatedBoundChecker _uninstantiatedBoundChecker;

  /// Setting this flag to `true` disables the check for conflicting generics.
  /// This is used when running with the old task model to work around
  /// dartbug.com/32421.
  ///
  /// TODO(paulberry): remove this flag once dartbug.com/32421 is properly
  /// fixed.
  final bool disableConflictingGenericsCheck;

  bool _isNonNullable = false;

  /**
   * Initialize a newly created error verifier.
   */
  ErrorVerifier(ErrorReporter errorReporter, this._currentLibrary,
      this._typeProvider, this._inheritanceManager, bool enableSuperMixins,
      {this.disableConflictingGenericsCheck: false})
      : _errorReporter = errorReporter,
        _uninstantiatedBoundChecker =
            new _UninstantiatedBoundChecker(errorReporter) {
    this._isInSystemLibrary = _currentLibrary.source.isInSystemLibrary;
    this._hasExtUri = _currentLibrary.hasExtUri;
    _isEnclosingConstructorConst = false;
    _isInCatchClause = false;
    _isInStaticVariableDeclaration = false;
    _isInInstanceVariableDeclaration = false;
    _isInInstanceVariableInitializer = false;
    _isInConstructorInitializer = false;
    _isInStaticMethod = false;
    _boolType = _typeProvider.boolType;
    _intType = _typeProvider.intType;
    _DISALLOWED_TYPES_TO_EXTEND_OR_IMPLEMENT = _typeProvider.nonSubtypableTypes;
    _typeSystem = _currentLibrary.context.typeSystem;
    _options = _currentLibrary.context.analysisOptions;
  }

  /**
   * If `true`, mixins are allowed to inherit from types other than Object, and
   * are allowed to reference `super`.
   */
  @deprecated
  bool get enableSuperMixins => false;

  ClassElement get enclosingClass => _enclosingClass;

  /**
   * For consumers of error verification as a library, (currently just the
   * angular plugin), expose a setter that can make the errors reported more
   * accurate when dangling code snippets are being resolved from a class
   * context. Note that this setter is very defensive for potential misuse; it
   * should not be modified in the middle of visiting a tree and requires an
   * analyzer-provided Impl instance to work.
   */
  set enclosingClass(ClassElement classElement) {
    assert(classElement is ClassElementImpl);
    assert(_enclosingClass == null);
    assert(_enclosingEnum == null);
    assert(_enclosingFunction == null);
    _enclosingClass = classElement;
  }

  @override
  void visitAnnotation(Annotation node) {
    _checkForInvalidAnnotationFromDeferredLibrary(node);
    _checkForMissingJSLibAnnotation(node);
    super.visitAnnotation(node);
  }

  @override
  void visitArgumentList(ArgumentList node) {
    _checkForArgumentTypesNotAssignableInList(node);
    super.visitArgumentList(node);
  }

  @override
  void visitAsExpression(AsExpression node) {
    _checkForTypeAnnotationDeferredClass(node.type);
    super.visitAsExpression(node);
  }

  @override
  void visitAssertInitializer(AssertInitializer node) {
    _checkForNonBoolExpression(node);
    super.visitAssertInitializer(node);
  }

  @override
  void visitAssertStatement(AssertStatement node) {
    _checkForNonBoolExpression(node);
    super.visitAssertStatement(node);
  }

  @override
  void visitAssignmentExpression(AssignmentExpression node) {
    TokenType operatorType = node.operator.type;
    Expression lhs = node.leftHandSide;
    Expression rhs = node.rightHandSide;
    if (operatorType == TokenType.EQ ||
        operatorType == TokenType.QUESTION_QUESTION_EQ) {
      _checkForInvalidAssignment(lhs, rhs);
    } else {
      _checkForInvalidCompoundAssignment(node, lhs, rhs);
      _checkForArgumentTypeNotAssignableForArgument(rhs);
      _checkForNullableDereference(lhs);
    }
    _checkForAssignmentToFinal(lhs);
    super.visitAssignmentExpression(node);
  }

  @override
  void visitAwaitExpression(AwaitExpression node) {
    if (!_inAsync) {
      _errorReporter.reportErrorForToken(
          CompileTimeErrorCode.AWAIT_IN_WRONG_CONTEXT, node.awaitKeyword);
    }
    super.visitAwaitExpression(node);
  }

  @override
  void visitBinaryExpression(BinaryExpression node) {
    Token operator = node.operator;
    TokenType type = operator.type;
    if (type == TokenType.AMPERSAND_AMPERSAND || type == TokenType.BAR_BAR) {
      String lexeme = operator.lexeme;
      _checkForAssignability(node.leftOperand, _boolType,
          StaticTypeWarningCode.NON_BOOL_OPERAND, [lexeme]);
      _checkForAssignability(node.rightOperand, _boolType,
          StaticTypeWarningCode.NON_BOOL_OPERAND, [lexeme]);
      _checkForUseOfVoidResult(node.rightOperand);
      _checkForNullableDereference(node.leftOperand);
      _checkForNullableDereference(node.rightOperand);
    } else if (type != TokenType.EQ_EQ &&
        type != TokenType.BANG_EQ &&
        type != TokenType.QUESTION_QUESTION) {
      _checkForArgumentTypeNotAssignableForArgument(node.rightOperand);
      _checkForNullableDereference(node.leftOperand);
    } else {
      _checkForArgumentTypeNotAssignableForArgument(node.rightOperand);
    }

    _checkForUseOfVoidResult(node.leftOperand);

    super.visitBinaryExpression(node);
  }

  @override
  void visitBlock(Block node) {
    _hiddenElements = new HiddenElements(_hiddenElements, node);
    try {
      _checkDuplicateDeclarationInStatements(node.statements);
      super.visitBlock(node);
    } finally {
      _hiddenElements = _hiddenElements.outerElements;
    }
  }

  @override
  void visitBlockFunctionBody(BlockFunctionBody node) {
    bool wasInAsync = _inAsync;
    bool wasInGenerator = _inGenerator;
    bool previousHasReturnWithoutValue = _hasReturnWithoutValue;
    _hasReturnWithoutValue = false;
    List<ReturnStatement> previousReturnsWith = _returnsWith;
    List<ReturnStatement> previousReturnsWithout = _returnsWithout;
    try {
      _inAsync = node.isAsynchronous;
      _inGenerator = node.isGenerator;
      _returnsWith = new List<ReturnStatement>();
      _returnsWithout = new List<ReturnStatement>();
      super.visitBlockFunctionBody(node);
      _checkForMixedReturns(node);
    } finally {
      _inAsync = wasInAsync;
      _inGenerator = wasInGenerator;
      _returnsWith = previousReturnsWith;
      _returnsWithout = previousReturnsWithout;
      _hasReturnWithoutValue = previousHasReturnWithoutValue;
    }
  }

  @override
  void visitBreakStatement(BreakStatement node) {
    SimpleIdentifier labelNode = node.label;
    if (labelNode != null) {
      Element labelElement = labelNode.staticElement;
      if (labelElement is LabelElementImpl && labelElement.isOnSwitchMember) {
        _errorReporter.reportErrorForNode(
            ResolverErrorCode.BREAK_LABEL_ON_SWITCH_MEMBER, labelNode);
      }
    }
  }

  void visitCascadeExpression(CascadeExpression node) {
    _checkForNullableDereference(node.target);
    super.visitCascadeExpression(node);
  }

  @override
  void visitCatchClause(CatchClause node) {
    _checkDuplicateDefinitionInCatchClause(node);
    bool previousIsInCatchClause = _isInCatchClause;
    try {
      _isInCatchClause = true;
      _checkForTypeAnnotationDeferredClass(node.exceptionType);
      _checkForPotentiallyNullableType(node.exceptionType);
      super.visitCatchClause(node);
    } finally {
      _isInCatchClause = previousIsInCatchClause;
    }
  }

  @override
  void visitClassDeclaration(ClassDeclaration node) {
    ClassElementImpl outerClass = _enclosingClass;
    try {
      _isInNativeClass = node.nativeClause != null;
      _enclosingClass = AbstractClassElementImpl.getImpl(node.declaredElement);

      List<ClassMember> members = node.members;
      _checkDuplicateClassMembers(members);
      _checkForBuiltInIdentifierAsName(
          node.name, CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE_NAME);
      _checkForMemberWithClassName();
      _checkForNoDefaultSuperConstructorImplicit(node);
      _checkForConflictingTypeVariableErrorCodes();
      TypeName superclass = node.extendsClause?.superclass;
      ImplementsClause implementsClause = node.implementsClause;
      WithClause withClause = node.withClause;

      // Only do error checks on the clause nodes if there is a non-null clause
      if (implementsClause != null ||
          superclass != null ||
          withClause != null) {
        _checkClassInheritance(node, superclass, withClause, implementsClause);
      }

      _initializeInitialFieldElementsMap(_enclosingClass.fields);
      _checkForFinalNotInitializedInClass(members);
      _checkForBadFunctionUse(node);
      super.visitClassDeclaration(node);
    } finally {
      _isInNativeClass = false;
      _initialFieldElementsMap = null;
      _enclosingClass = outerClass;
    }
  }

  @override
  void visitClassTypeAlias(ClassTypeAlias node) {
    _checkForBuiltInIdentifierAsName(
        node.name, CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPEDEF_NAME);
    ClassElementImpl outerClassElement = _enclosingClass;
    try {
      _enclosingClass = AbstractClassElementImpl.getImpl(node.declaredElement);
      _checkClassInheritance(
          node, node.superclass, node.withClause, node.implementsClause);
    } finally {
      _enclosingClass = outerClassElement;
    }
    super.visitClassTypeAlias(node);
  }

  @override
  void visitComment(Comment node) {
    _isInComment = true;
    try {
      super.visitComment(node);
    } finally {
      _isInComment = false;
    }
  }

  @override
  void visitCompilationUnit(CompilationUnit node) {
    _isNonNullable = (node as CompilationUnitImpl).isNonNullable;
    _checkDuplicateUnitMembers(node);
    _checkForDeferredPrefixCollisions(node);
    super.visitCompilationUnit(node);
    _isNonNullable = false;
  }

  @override
  void visitConditionalExpression(ConditionalExpression node) {
    _checkForNonBoolCondition(node.condition);
    super.visitConditionalExpression(node);
  }

  @override
  void visitConstructorDeclaration(ConstructorDeclaration node) {
    ExecutableElement outerFunction = _enclosingFunction;
    try {
      ConstructorElement constructorElement = node.declaredElement;
      _enclosingFunction = constructorElement;
      _isEnclosingConstructorConst = node.constKeyword != null;
      _isInFactory = node.factoryKeyword != null;
      _checkForInvalidModifierOnBody(
          node.body, CompileTimeErrorCode.INVALID_MODIFIER_ON_CONSTRUCTOR);
      _checkForConstConstructorWithNonFinalField(node, constructorElement);
      _checkForConstConstructorWithNonConstSuper(node);
      _checkForAllFinalInitializedErrorCodes(node);
      _checkForRedirectingConstructorErrorCodes(node);
      _checkForMixinDeclaresConstructor(node);
      _checkForMultipleSuperInitializers(node);
      _checkForRecursiveConstructorRedirect(node, constructorElement);
      if (!_checkForRecursiveFactoryRedirect(node, constructorElement)) {
        _checkForAllRedirectConstructorErrorCodes(node);
      }
      _checkForUndefinedConstructorInInitializerImplicit(node);
      _checkForRedirectToNonConstConstructor(node, constructorElement);
      _checkForReturnInGenerativeConstructor(node);
      super.visitConstructorDeclaration(node);
    } finally {
      _isEnclosingConstructorConst = false;
      _isInFactory = false;
      _enclosingFunction = outerFunction;
    }
  }

  @override
  void visitConstructorFieldInitializer(ConstructorFieldInitializer node) {
    _isInConstructorInitializer = true;
    try {
      SimpleIdentifier fieldName = node.fieldName;
      Element staticElement = fieldName.staticElement;
      _checkForInvalidField(node, fieldName, staticElement);
      if (staticElement is FieldElement) {
        _checkForFieldInitializerNotAssignable(node, staticElement);
      }
      super.visitConstructorFieldInitializer(node);
    } finally {
      _isInConstructorInitializer = false;
    }
  }

  @override
  void visitContinueStatement(ContinueStatement node) {
    SimpleIdentifier labelNode = node.label;
    if (labelNode != null) {
      Element labelElement = labelNode.staticElement;
      if (labelElement is LabelElementImpl &&
          labelElement.isOnSwitchStatement) {
        _errorReporter.reportErrorForNode(
            ResolverErrorCode.CONTINUE_LABEL_ON_SWITCH, labelNode);
      }
    }
  }

  @override
  void visitDefaultFormalParameter(DefaultFormalParameter node) {
    _checkForInvalidAssignment(node.identifier, node.defaultValue);
    _checkForDefaultValueInFunctionTypedParameter(node);
    super.visitDefaultFormalParameter(node);
  }

  @override
  void visitDoStatement(DoStatement node) {
    _checkForNonBoolCondition(node.condition);
    super.visitDoStatement(node);
  }

  @override
  void visitEnumDeclaration(EnumDeclaration node) {
    ClassElement outerEnum = _enclosingEnum;
    try {
      _enclosingEnum = node.declaredElement;
      _checkDuplicateEnumMembers(node);
      super.visitEnumDeclaration(node);
    } finally {
      _enclosingEnum = outerEnum;
    }
  }

  @override
  void visitExportDirective(ExportDirective node) {
    ExportElement exportElement = node.element;
    if (exportElement != null) {
      LibraryElement exportedLibrary = exportElement.exportedLibrary;
      _checkForAmbiguousExport(node, exportElement, exportedLibrary);
      _checkForExportDuplicateLibraryName(node, exportElement, exportedLibrary);
      _checkForExportInternalLibrary(node, exportElement);
    }
    super.visitExportDirective(node);
  }

  @override
  void visitExpressionFunctionBody(ExpressionFunctionBody node) {
    bool wasInAsync = _inAsync;
    bool wasInGenerator = _inGenerator;
    try {
      _inAsync = node.isAsynchronous;
      _inGenerator = node.isGenerator;
      FunctionType functionType = _enclosingFunction?.type;
      DartType expectedReturnType = functionType == null
          ? DynamicTypeImpl.instance
          : functionType.returnType;
      ExecutableElement function = _enclosingFunction;
      bool isSetterWithImplicitReturn = function.hasImplicitReturnType &&
          function is PropertyAccessorElement &&
          function.isSetter;
      if (!isSetterWithImplicitReturn) {
        _checkForReturnOfInvalidType(node.expression, expectedReturnType,
            isArrowFunction: true);
      }
      super.visitExpressionFunctionBody(node);
    } finally {
      _inAsync = wasInAsync;
      _inGenerator = wasInGenerator;
    }
  }

  @override
  void visitFieldDeclaration(FieldDeclaration node) {
    _isInStaticVariableDeclaration = node.isStatic;
    _isInInstanceVariableDeclaration = !_isInStaticVariableDeclaration;
    if (_isInInstanceVariableDeclaration) {
      VariableDeclarationList variables = node.fields;
      if (variables.isConst) {
        _errorReporter.reportErrorForToken(
            CompileTimeErrorCode.CONST_INSTANCE_FIELD, variables.keyword);
      }
    }
    try {
      super.visitFieldDeclaration(node);
    } finally {
      _isInStaticVariableDeclaration = false;
      _isInInstanceVariableDeclaration = false;
    }
  }

  @override
  void visitFieldFormalParameter(FieldFormalParameter node) {
    _checkForValidField(node);
    _checkForConstFormalParameter(node);
    _checkForPrivateOptionalParameter(node);
    _checkForFieldInitializingFormalRedirectingConstructor(node);
    _checkForTypeAnnotationDeferredClass(node.type);
    super.visitFieldFormalParameter(node);
  }

  @override
  void visitForEachPartsWithDeclaration(ForEachPartsWithDeclaration node) {
    DeclaredIdentifier loopVariable = node.loopVariable;
    if (loopVariable == null) {
      // Ignore malformed for statements.
      return;
    }
    if (_checkForEachParts(node, loopVariable.identifier)) {
      if (loopVariable.isConst) {
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.FOR_IN_WITH_CONST_VARIABLE, loopVariable);
      }
    }
    super.visitForEachPartsWithDeclaration(node);
  }

  @override
  void visitForEachPartsWithIdentifier(ForEachPartsWithIdentifier node) {
    SimpleIdentifier identifier = node.identifier;
    if (identifier == null) {
      // Ignore malformed for statements.
      return;
    }
    if (_checkForEachParts(node, identifier)) {
      Element variableElement = identifier.staticElement;
      if (variableElement is VariableElement && variableElement.isConst) {
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.FOR_IN_WITH_CONST_VARIABLE, identifier);
      }
    }
    super.visitForEachPartsWithIdentifier(node);
  }

  @override
  void visitFormalParameterList(FormalParameterList node) {
    _checkDuplicateDefinitionInParameterList(node);
    _checkUseOfCovariantInParameters(node);
    super.visitFormalParameterList(node);
  }

  @override
  void visitForPartsWithDeclarations(ForPartsWithDeclarations node) {
    if (node.condition != null) {
      _checkForNonBoolCondition(node.condition);
    }
    if (node.variables != null) {
      _checkDuplicateVariables(node.variables);
    }
    super.visitForPartsWithDeclarations(node);
  }

  @override
  void visitForPartsWithExpression(ForPartsWithExpression node) {
    if (node.condition != null) {
      _checkForNonBoolCondition(node.condition);
    }
    super.visitForPartsWithExpression(node);
  }

  @override
  void visitFunctionDeclaration(FunctionDeclaration node) {
    ExecutableElement functionElement = node.declaredElement;
    if (functionElement != null &&
        functionElement.enclosingElement is! CompilationUnitElement) {
      _hiddenElements.declare(functionElement);
    }
    ExecutableElement outerFunction = _enclosingFunction;
    try {
      SimpleIdentifier identifier = node.name;
      String methodName = "";
      if (identifier != null) {
        methodName = identifier.name;
      }
      _enclosingFunction = functionElement;
      TypeAnnotation returnType = node.returnType;
      if (node.isSetter || node.isGetter) {
        _checkForMismatchedAccessorTypes(node, methodName);
        if (node.isSetter) {
          FunctionExpression functionExpression = node.functionExpression;
          if (functionExpression != null) {
            _checkForWrongNumberOfParametersForSetter(
                identifier, functionExpression.parameters);
          }
          _checkForNonVoidReturnTypeForSetter(returnType);
        }
      }
      if (node.isSetter) {
        _checkForInvalidModifierOnBody(node.functionExpression.body,
            CompileTimeErrorCode.INVALID_MODIFIER_ON_SETTER);
      }
      _checkForTypeAnnotationDeferredClass(returnType);
      _checkForIllegalReturnType(returnType);
      _checkForImplicitDynamicReturn(node.name, node.declaredElement);
      super.visitFunctionDeclaration(node);
    } finally {
      _enclosingFunction = outerFunction;
    }
  }

  @override
  void visitFunctionExpression(FunctionExpression node) {
    // If this function expression is wrapped in a function declaration, don't
    // change the enclosingFunction field.
    if (node.parent is! FunctionDeclaration) {
      ExecutableElement outerFunction = _enclosingFunction;
      try {
        _enclosingFunction = node.declaredElement;
        super.visitFunctionExpression(node);
      } finally {
        _enclosingFunction = outerFunction;
      }
    } else {
      super.visitFunctionExpression(node);
    }
  }

  @override
  void visitFunctionExpressionInvocation(FunctionExpressionInvocation node) {
    Expression functionExpression = node.function;
    DartType expressionType = functionExpression.staticType;
    if (!_checkForNullableDereference(functionExpression) &&
        !_checkForUseOfVoidResult(functionExpression) &&
        !_isFunctionType(expressionType)) {
      _errorReporter.reportErrorForNode(
          StaticTypeWarningCode.INVOCATION_OF_NON_FUNCTION_EXPRESSION,
          functionExpression);
    } else if (expressionType is FunctionType) {
      _checkTypeArguments(node);
    }
    _checkForImplicitDynamicInvoke(node);
    _checkForNullableDereference(node.function);
    super.visitFunctionExpressionInvocation(node);
  }

  @override
  void visitFunctionTypeAlias(FunctionTypeAlias node) {
    _checkForBuiltInIdentifierAsName(
        node.name, CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPEDEF_NAME);
    _checkForDefaultValueInFunctionTypeAlias(node);
    _checkForTypeAliasCannotReferenceItself_function(node);
    super.visitFunctionTypeAlias(node);
  }

  @override
  void visitFunctionTypedFormalParameter(FunctionTypedFormalParameter node) {
    bool old = _isInFunctionTypedFormalParameter;
    _isInFunctionTypedFormalParameter = true;
    try {
      _checkForTypeAnnotationDeferredClass(node.returnType);

      // TODO(jmesserly): ideally we'd use _checkForImplicitDynamicReturn, and
      // we can get the function element via `node?.element?.type?.element` but
      // it doesn't have hasImplicitReturnType set correctly.
      if (!_options.implicitDynamic && node.returnType == null) {
        DartType parameterType =
            resolutionMap.elementDeclaredByFormalParameter(node).type;
        if (parameterType is FunctionType &&
            parameterType.returnType.isDynamic) {
          _errorReporter.reportErrorForNode(
              StrongModeCode.IMPLICIT_DYNAMIC_RETURN,
              node.identifier,
              [node.identifier]);
        }
      }

      // TODO(paulberry): remove this once dartbug.com/28515 is fixed.
      if (node.typeParameters != null) {
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.GENERIC_FUNCTION_TYPED_PARAM_UNSUPPORTED,
            node);
      }

      super.visitFunctionTypedFormalParameter(node);
    } finally {
      _isInFunctionTypedFormalParameter = old;
    }
  }

  @override
  void visitGenericTypeAlias(GenericTypeAlias node) {
    if (_hasTypedefSelfReference(node.declaredElement)) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.TYPE_ALIAS_CANNOT_REFERENCE_ITSELF, node);
    }
    super.visitGenericTypeAlias(node);
  }

  @override
  void visitIfElement(IfElement node) {
    _checkForNonBoolCondition(node.condition);
    super.visitIfElement(node);
  }

  @override
  void visitIfStatement(IfStatement node) {
    _checkForNonBoolCondition(node.condition);
    super.visitIfStatement(node);
  }

  @override
  void visitImplementsClause(ImplementsClause node) {
    node.interfaces.forEach(_checkForImplicitDynamicType);
    super.visitImplementsClause(node);
  }

  @override
  void visitImportDirective(ImportDirective node) {
    ImportElement importElement = node.element;
    if (node.prefix != null) {
      _checkForBuiltInIdentifierAsName(
          node.prefix, CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_PREFIX_NAME);
    }
    if (importElement != null) {
      _checkForImportDuplicateLibraryName(node, importElement);
      _checkForImportInternalLibrary(node, importElement);
    }
    super.visitImportDirective(node);
  }

  @override
  void visitIndexExpression(IndexExpression node) {
    _checkForArgumentTypeNotAssignableForArgument(node.index);
    _checkForNullableDereference(node.target);
    super.visitIndexExpression(node);
  }

  @override
  void visitInstanceCreationExpression(InstanceCreationExpression node) {
    bool wasInConstInstanceCreation = _isInConstInstanceCreation;
    _isInConstInstanceCreation = node.isConst;
    try {
      ConstructorName constructorName = node.constructorName;
      TypeName typeName = constructorName.type;
      DartType type = typeName.type;
      if (type is InterfaceType) {
        _checkForConstOrNewWithAbstractClass(node, typeName, type);
        _checkForConstOrNewWithEnum(node, typeName, type);
        _checkForConstOrNewWithMixin(node, typeName, type);
        if (_isInConstInstanceCreation) {
          _checkForConstWithNonConst(node);
          _checkForConstWithUndefinedConstructor(
              node, constructorName, typeName);
          _checkForConstDeferredClass(node, constructorName, typeName);
        } else {
          _checkForNewWithUndefinedConstructor(node, constructorName, typeName);
        }
      }
      _checkForImplicitDynamicType(typeName);
      super.visitInstanceCreationExpression(node);
    } finally {
      _isInConstInstanceCreation = wasInConstInstanceCreation;
    }
  }

  @override
  void visitIntegerLiteral(IntegerLiteral node) {
    _checkForOutOfRange(node);
    super.visitIntegerLiteral(node);
  }

  @override
  void visitInterpolationExpression(InterpolationExpression node) {
    _checkForUseOfVoidResult(node.expression);
    super.visitInterpolationExpression(node);
  }

  @override
  void visitIsExpression(IsExpression node) {
    _checkForTypeAnnotationDeferredClass(node.type);
    _checkForUseOfVoidResult(node.expression);
    super.visitIsExpression(node);
  }

  @override
  void visitListLiteral(ListLiteral node) {
    TypeArgumentList typeArguments = node.typeArguments;
    if (typeArguments != null) {
      if (node.isConst) {
        NodeList<TypeAnnotation> arguments = typeArguments.arguments;
        if (arguments.isNotEmpty) {
          _checkForInvalidTypeArgumentInConstTypedLiteral(arguments,
              CompileTimeErrorCode.INVALID_TYPE_ARGUMENT_IN_CONST_LIST);
        }
      }
      _checkTypeArgumentCount(typeArguments, 1,
          StaticTypeWarningCode.EXPECTED_ONE_LIST_TYPE_ARGUMENTS);
    }
    _checkForInferenceFailureOnCollectionLiteral(node);
    _checkForImplicitDynamicTypedLiteral(node);
    _checkForListElementTypeNotAssignable(node);

    super.visitListLiteral(node);
  }

  @override
  void visitMethodDeclaration(MethodDeclaration node) {
    ExecutableElement previousFunction = _enclosingFunction;
    try {
      _isInStaticMethod = node.isStatic;
      _enclosingFunction = node.declaredElement;
      TypeAnnotation returnType = node.returnType;
      if (node.isSetter) {
        _checkForInvalidModifierOnBody(
            node.body, CompileTimeErrorCode.INVALID_MODIFIER_ON_SETTER);
        _checkForWrongNumberOfParametersForSetter(node.name, node.parameters);
        _checkForNonVoidReturnTypeForSetter(returnType);
      } else if (node.isOperator) {
        _checkForOptionalParameterInOperator(node);
        _checkForWrongNumberOfParametersForOperator(node);
        _checkForNonVoidReturnTypeForOperator(node);
      }
      _checkForTypeAnnotationDeferredClass(returnType);
      _checkForIllegalReturnType(returnType);
      _checkForImplicitDynamicReturn(node, node.declaredElement);
      _checkForMustCallSuper(node);
      super.visitMethodDeclaration(node);
    } finally {
      _enclosingFunction = previousFunction;
      _isInStaticMethod = false;
    }
  }

  @override
  void visitMethodInvocation(MethodInvocation node) {
    Expression target = node.realTarget;
    SimpleIdentifier methodName = node.methodName;
    if (target != null) {
      ClassElement typeReference = ElementResolver.getTypeReference(target);
      _checkForStaticAccessToInstanceMember(typeReference, methodName);
      _checkForInstanceAccessToStaticMember(typeReference, methodName);
      _checkForUnnecessaryNullAware(target, node.operator);
    } else {
      _checkForUnqualifiedReferenceToNonLocalStaticMember(methodName);
      _checkForNullableDereference(node.function);
    }
    _checkTypeArguments(node);
    _checkForImplicitDynamicInvoke(node);
    if (node.operator?.type != TokenType.QUESTION_PERIOD &&
        methodName.name != 'toString' &&
        methodName.name != 'noSuchMethod') {
      _checkForNullableDereference(target);
    }
    super.visitMethodInvocation(node);
  }

  @override
  void visitMixinDeclaration(MixinDeclaration node) {
    // TODO(scheglov) Verify for all mixin errors.
    ClassElementImpl outerClass = _enclosingClass;
    try {
      _enclosingClass = AbstractClassElementImpl.getImpl(node.declaredElement);

      List<ClassMember> members = node.members;
      _checkDuplicateClassMembers(members);
      _checkForBuiltInIdentifierAsName(
          node.name, CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE_NAME);
      _checkForMemberWithClassName();
      _checkForConflictingTypeVariableErrorCodes();

      OnClause onClause = node.onClause;
      ImplementsClause implementsClause = node.implementsClause;

      // Only do error checks only if there is a non-null clause.
      if (onClause != null || implementsClause != null) {
        _checkMixinInheritance(node, onClause, implementsClause);
      }

      _initializeInitialFieldElementsMap(_enclosingClass.fields);
      _checkForFinalNotInitializedInClass(members);
      //      _checkForBadFunctionUse(node);
      super.visitMixinDeclaration(node);
    } finally {
      _initialFieldElementsMap = null;
      _enclosingClass = outerClass;
    }
  }

  @override
  void visitNativeClause(NativeClause node) {
    // TODO(brianwilkerson) Figure out the right rule for when 'native' is
    // allowed.
    if (!_isInSystemLibrary) {
      _errorReporter.reportErrorForNode(
          ParserErrorCode.NATIVE_CLAUSE_IN_NON_SDK_CODE, node);
    }
    super.visitNativeClause(node);
  }

  @override
  void visitNativeFunctionBody(NativeFunctionBody node) {
    _checkForNativeFunctionBodyInNonSdkCode(node);
    super.visitNativeFunctionBody(node);
  }

  @override
  void visitPostfixExpression(PostfixExpression node) {
    if (node.operator.type != TokenType.BANG) {
      _checkForAssignmentToFinal(node.operand);
      _checkForIntNotAssignable(node.operand);
      _checkForNullableDereference(node.operand);
    }
    super.visitPostfixExpression(node);
  }

  @override
  void visitPrefixedIdentifier(PrefixedIdentifier node) {
    if (node.parent is! Annotation) {
      ClassElement typeReference =
          ElementResolver.getTypeReference(node.prefix);
      SimpleIdentifier name = node.identifier;
      _checkForStaticAccessToInstanceMember(typeReference, name);
      _checkForInstanceAccessToStaticMember(typeReference, name);
    }
    String property = node.identifier.name;
    if (node.staticElement is ExecutableElement &&
        property != 'hashCode' &&
        property != 'runtimeType') {
      _checkForNullableDereference(node.prefix);
    }
    super.visitPrefixedIdentifier(node);
  }

  @override
  void visitPrefixExpression(PrefixExpression node) {
    TokenType operatorType = node.operator.type;
    Expression operand = node.operand;
    if (operatorType == TokenType.BANG) {
      _checkForNonBoolNegationExpression(operand);
    } else if (operatorType.isIncrementOperator) {
      _checkForAssignmentToFinal(operand);
    }
    _checkForIntNotAssignable(operand);
    _checkForNullableDereference(operand);
    _checkForUseOfVoidResult(operand);
    super.visitPrefixExpression(node);
  }

  @override
  void visitPropertyAccess(PropertyAccess node) {
    ClassElement typeReference =
        ElementResolver.getTypeReference(node.realTarget);
    SimpleIdentifier propertyName = node.propertyName;
    _checkForStaticAccessToInstanceMember(typeReference, propertyName);
    _checkForInstanceAccessToStaticMember(typeReference, propertyName);
    if (node.operator?.type != TokenType.QUESTION_PERIOD &&
        propertyName.name != 'hashCode' &&
        propertyName.name != 'runtimeType') {
      _checkForNullableDereference(node.target);
    }
    _checkForUnnecessaryNullAware(node.target, node.operator);
    super.visitPropertyAccess(node);
  }

  @override
  void visitRedirectingConstructorInvocation(
      RedirectingConstructorInvocation node) {
    _isInConstructorInitializer = true;
    try {
      super.visitRedirectingConstructorInvocation(node);
    } finally {
      _isInConstructorInitializer = false;
    }
  }

  @override
  void visitRethrowExpression(RethrowExpression node) {
    _checkForRethrowOutsideCatch(node);
    super.visitRethrowExpression(node);
  }

  @override
  void visitReturnStatement(ReturnStatement node) {
    if (node.expression == null) {
      _returnsWithout.add(node);
    } else {
      _returnsWith.add(node);
    }
    _checkForAllReturnStatementErrorCodes(node);
    super.visitReturnStatement(node);
  }

  @override
  void visitSetOrMapLiteral(SetOrMapLiteral node) {
    TypeArgumentList typeArguments = node.typeArguments;
    if (node.isMap) {
      if (typeArguments != null) {
        NodeList<TypeAnnotation> arguments = typeArguments.arguments;
        if (node.isConst) {
          if (arguments.isNotEmpty) {
            _checkForInvalidTypeArgumentInConstTypedLiteral(arguments,
                CompileTimeErrorCode.INVALID_TYPE_ARGUMENT_IN_CONST_MAP);
          }
        }
        _checkTypeArgumentCount(typeArguments, 2,
            StaticTypeWarningCode.EXPECTED_TWO_MAP_TYPE_ARGUMENTS);
      }
      _checkForInferenceFailureOnCollectionLiteral(node);
      _checkForImplicitDynamicTypedLiteral(node);
      _checkForMapTypeNotAssignable(node);
      _checkForNonConstMapAsExpressionStatement3(node);
    } else if (node.isSet) {
      if (typeArguments != null) {
        if (node.isConst) {
          NodeList<TypeAnnotation> arguments = typeArguments.arguments;
          if (arguments.isNotEmpty) {
            _checkForInvalidTypeArgumentInConstTypedLiteral(arguments,
                CompileTimeErrorCode.INVALID_TYPE_ARGUMENT_IN_CONST_SET);
          }
        }
        _checkTypeArgumentCount(typeArguments, 1,
            StaticTypeWarningCode.EXPECTED_ONE_SET_TYPE_ARGUMENTS);
      }
      _checkForInferenceFailureOnCollectionLiteral(node);
      _checkForImplicitDynamicTypedLiteral(node);
      _checkForSetElementTypeNotAssignable3(node);
    }
    super.visitSetOrMapLiteral(node);
  }

  @override
  void visitSimpleFormalParameter(SimpleFormalParameter node) {
    _checkForConstFormalParameter(node);
    _checkForPrivateOptionalParameter(node);
    _checkForTypeAnnotationDeferredClass(node.type);

    // Checks for an implicit dynamic parameter type.
    //
    // We can skip other parameter kinds besides simple formal, because:
    // - DefaultFormalParameter contains a simple one, so it gets here,
    // - FieldFormalParameter error should be reported on the field,
    // - FunctionTypedFormalParameter is a function type, not dynamic.
    _checkForImplicitDynamicIdentifier(node, node.identifier);

    super.visitSimpleFormalParameter(node);
  }

  @override
  void visitSimpleIdentifier(SimpleIdentifier node) {
    _checkForAmbiguousImport(node);
    _checkForReferenceBeforeDeclaration(node);
    _checkForImplicitThisReferenceInInitializer(node);
    _checkForTypeParameterReferencedByStatic(node);
    if (!_isUnqualifiedReferenceToNonLocalStaticMemberAllowed(node)) {
      _checkForUnqualifiedReferenceToNonLocalStaticMember(node);
    }
    super.visitSimpleIdentifier(node);
  }

  @override
  void visitSuperConstructorInvocation(SuperConstructorInvocation node) {
    _isInConstructorInitializer = true;
    try {
      super.visitSuperConstructorInvocation(node);
    } finally {
      _isInConstructorInitializer = false;
    }
  }

  @override
  void visitSwitchCase(SwitchCase node) {
    _checkDuplicateDeclarationInStatements(node.statements);
    super.visitSwitchCase(node);
  }

  @override
  void visitSwitchDefault(SwitchDefault node) {
    _checkDuplicateDeclarationInStatements(node.statements);
    super.visitSwitchDefault(node);
  }

  @override
  void visitSwitchStatement(SwitchStatement node) {
    _checkForSwitchExpressionNotAssignable(node);
    _checkForCaseBlocksNotTerminated(node);
    _checkForMissingEnumConstantInSwitch(node);
    super.visitSwitchStatement(node);
  }

  @override
  void visitThisExpression(ThisExpression node) {
    _checkForInvalidReferenceToThis(node);
    super.visitThisExpression(node);
  }

  @override
  void visitThrowExpression(ThrowExpression node) {
    _checkForConstEvalThrowsException(node);
    _checkForNullableDereference(node.expression);
    _checkForUseOfVoidResult(node.expression);
    super.visitThrowExpression(node);
  }

  @override
  void visitTopLevelVariableDeclaration(TopLevelVariableDeclaration node) {
    _checkForFinalNotInitialized(node.variables);
    super.visitTopLevelVariableDeclaration(node);
  }

  @override
  void visitTypeArgumentList(TypeArgumentList node) {
    NodeList<TypeAnnotation> list = node.arguments;
    for (TypeAnnotation type in list) {
      _checkForTypeAnnotationDeferredClass(type);
    }
    super.visitTypeArgumentList(node);
  }

  @override
  void visitTypeName(TypeName node) {
    _checkForTypeArgumentNotMatchingBounds(node);
    if (node.parent is ConstructorName &&
        node.parent.parent is InstanceCreationExpression) {
      _checkForInferenceFailureOnInstanceCreation(node, node.parent.parent);
    } else {
      _checkForRawTypeName(node);
    }
    super.visitTypeName(node);
  }

  @override
  void visitTypeParameter(TypeParameter node) {
    _checkForBuiltInIdentifierAsName(node.name,
        CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE_PARAMETER_NAME);
    _checkForTypeParameterSupertypeOfItsBound(node);
    _checkForTypeAnnotationDeferredClass(node.bound);
    _checkForImplicitDynamicType(node.bound);
    _checkForGenericFunctionType(node.bound);
    node.bound?.accept(_uninstantiatedBoundChecker);
    super.visitTypeParameter(node);
  }

  @override
  void visitTypeParameterList(TypeParameterList node) {
    _checkDuplicateDefinitionInTypeParameterList(node);
    super.visitTypeParameterList(node);
  }

  @override
  void visitVariableDeclaration(VariableDeclaration node) {
    SimpleIdentifier nameNode = node.name;
    Expression initializerNode = node.initializer;
    // do checks
    _checkForInvalidAssignment(nameNode, initializerNode);
    _checkForImplicitDynamicIdentifier(node, nameNode);
    // visit name
    nameNode.accept(this);
    // visit initializer
    String name = nameNode.name;
    _namesForReferenceToDeclaredVariableInInitializer.add(name);
    bool wasInInstanceVariableInitializer = _isInInstanceVariableInitializer;
    _isInInstanceVariableInitializer = _isInInstanceVariableDeclaration;
    try {
      if (initializerNode != null) {
        initializerNode.accept(this);
      }
    } finally {
      _isInInstanceVariableInitializer = wasInInstanceVariableInitializer;
      _namesForReferenceToDeclaredVariableInInitializer.remove(name);
    }
    // declare the variable
    AstNode grandparent = node.parent.parent;
    if (grandparent is! TopLevelVariableDeclaration &&
        grandparent is! FieldDeclaration) {
      VariableElement element = node.declaredElement;
      if (element != null) {
        // There is no hidden elements if we are outside of a function body,
        // which will happen for variables declared in control flow elements.
        _hiddenElements?.declare(element);
      }
    }
  }

  @override
  void visitVariableDeclarationList(VariableDeclarationList node) {
    _checkForTypeAnnotationDeferredClass(node.type);
    super.visitVariableDeclarationList(node);
  }

  @override
  void visitVariableDeclarationStatement(VariableDeclarationStatement node) {
    _checkForFinalNotInitialized(node.variables);
    super.visitVariableDeclarationStatement(node);
  }

  @override
  void visitWhileStatement(WhileStatement node) {
    _checkForNonBoolCondition(node.condition);
    super.visitWhileStatement(node);
  }

  @override
  void visitWithClause(WithClause node) {
    node.mixinTypes.forEach(_checkForImplicitDynamicType);
    super.visitWithClause(node);
  }

  @override
  void visitYieldStatement(YieldStatement node) {
    if (_inGenerator) {
      _checkForYieldOfInvalidType(node.expression, node.star != null);
      if (node.star != null) {
        _checkForNullableDereference(node.expression);
      }
    } else {
      CompileTimeErrorCode errorCode;
      if (node.star != null) {
        errorCode = CompileTimeErrorCode.YIELD_EACH_IN_NON_GENERATOR;
      } else {
        errorCode = CompileTimeErrorCode.YIELD_IN_NON_GENERATOR;
      }
      _errorReporter.reportErrorForNode(errorCode, node);
    }
    _checkForUseOfVoidResult(node.expression);
    super.visitYieldStatement(node);
  }

  /**
   * Checks the class for problems with the superclass, mixins, or implemented
   * interfaces.
   */
  void _checkClassInheritance(
      NamedCompilationUnitMember node,
      TypeName superclass,
      WithClause withClause,
      ImplementsClause implementsClause) {
    // Only check for all of the inheritance logic around clauses if there
    // isn't an error code such as "Cannot extend double" already on the
    // class.
    if (!_checkForExtendsDisallowedClass(superclass) &&
        !_checkForImplementsClauseErrorCodes(implementsClause) &&
        !_checkForAllMixinErrorCodes(withClause)) {
      _checkForImplicitDynamicType(superclass);
      _checkForExtendsDeferredClass(superclass);
      _checkForConflictingClassMembers();
      _checkForRepeatedType(implementsClause?.interfaces,
          CompileTimeErrorCode.IMPLEMENTS_REPEATED);
      _checkImplementsSuperClass(implementsClause);
      _checkMixinInference(node, withClause);
      _checkForMixinWithConflictingPrivateMember(withClause, superclass);
      if (!disableConflictingGenericsCheck) {
        _checkForConflictingGenerics(node);
      }
    }
  }

  /**
   * Given a list of [directives] that have the same prefix, generate an error
   * if there is more than one import and any of those imports is deferred.
   *
   * See [CompileTimeErrorCode.SHARED_DEFERRED_PREFIX].
   */
  void _checkDeferredPrefixCollision(List<ImportDirective> directives) {
    int count = directives.length;
    if (count > 1) {
      for (int i = 0; i < count; i++) {
        Token deferredToken = directives[i].deferredKeyword;
        if (deferredToken != null) {
          _errorReporter.reportErrorForToken(
              CompileTimeErrorCode.SHARED_DEFERRED_PREFIX, deferredToken);
        }
      }
    }
  }

  /**
   * Check that there are no members with the same name.
   */
  void _checkDuplicateClassMembers(List<ClassMember> members) {
    Set<String> constructorNames = new HashSet<String>();
    Map<String, Element> instanceGetters = new HashMap<String, Element>();
    Map<String, Element> instanceSetters = new HashMap<String, Element>();
    Map<String, Element> staticGetters = new HashMap<String, Element>();
    Map<String, Element> staticSetters = new HashMap<String, Element>();

    for (ClassMember member in members) {
      if (member is ConstructorDeclaration) {
        var name = member.name?.name ?? '';
        if (!constructorNames.add(name)) {
          if (name.isEmpty) {
            _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.DUPLICATE_CONSTRUCTOR_DEFAULT, member);
          } else {
            _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.DUPLICATE_CONSTRUCTOR_NAME,
                member,
                [name]);
          }
        }
      } else if (member is FieldDeclaration) {
        for (VariableDeclaration field in member.fields.variables) {
          SimpleIdentifier identifier = field.name;
          _checkDuplicateIdentifier(
            member.isStatic ? staticGetters : instanceGetters,
            identifier,
            setterScope: member.isStatic ? staticSetters : instanceSetters,
          );
        }
      } else if (member is MethodDeclaration) {
        _checkDuplicateIdentifier(
          member.isStatic ? staticGetters : instanceGetters,
          member.name,
          setterScope: member.isStatic ? staticSetters : instanceSetters,
        );
      }
    }

    // Check for local static members conflicting with local instance members.
    for (ClassMember member in members) {
      if (member is ConstructorDeclaration) {
        if (member.name != null) {
          String name = member.name.name;
          var staticMember = staticGetters[name] ?? staticSetters[name];
          if (staticMember != null) {
            if (staticMember is PropertyAccessorElement) {
              _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.CONFLICTING_CONSTRUCTOR_AND_STATIC_FIELD,
                member.name,
                [name],
              );
            } else {
              _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.CONFLICTING_CONSTRUCTOR_AND_STATIC_METHOD,
                member.name,
                [name],
              );
            }
          }
        }
      } else if (member is FieldDeclaration) {
        if (member.isStatic) {
          for (VariableDeclaration field in member.fields.variables) {
            SimpleIdentifier identifier = field.name;
            String name = identifier.name;
            if (instanceGetters.containsKey(name) ||
                instanceSetters.containsKey(name)) {
              String className = _enclosingClass.displayName;
              _errorReporter.reportErrorForNode(
                  CompileTimeErrorCode.CONFLICTING_STATIC_AND_INSTANCE,
                  identifier,
                  [className, name, className]);
            }
          }
        }
      } else if (member is MethodDeclaration) {
        if (member.isStatic) {
          SimpleIdentifier identifier = member.name;
          String name = identifier.name;
          if (instanceGetters.containsKey(name) ||
              instanceSetters.containsKey(name)) {
            String className = identifier.staticElement.enclosingElement.name;
            _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.CONFLICTING_STATIC_AND_INSTANCE,
                identifier,
                [className, name, className]);
          }
        }
      }
    }
  }

  /**
   * Check that all of the parameters have unique names.
   */
  void _checkDuplicateDeclarationInStatements(List<Statement> statements) {
    Map<String, Element> definedNames = new HashMap<String, Element>();
    for (Statement statement in statements) {
      if (statement is VariableDeclarationStatement) {
        for (VariableDeclaration variable in statement.variables.variables) {
          _checkDuplicateIdentifier(definedNames, variable.name);
        }
      } else if (statement is FunctionDeclarationStatement) {
        _checkDuplicateIdentifier(
            definedNames, statement.functionDeclaration.name);
      }
    }
  }

  /**
   * Check that the exception and stack trace parameters have different names.
   */
  void _checkDuplicateDefinitionInCatchClause(CatchClause node) {
    SimpleIdentifier exceptionParameter = node.exceptionParameter;
    SimpleIdentifier stackTraceParameter = node.stackTraceParameter;
    if (exceptionParameter != null && stackTraceParameter != null) {
      String exceptionName = exceptionParameter.name;
      if (exceptionName == stackTraceParameter.name) {
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.DUPLICATE_DEFINITION,
            stackTraceParameter,
            [exceptionName]);
      }
    }
  }

  /**
   * Check that all of the parameters have unique names.
   */
  void _checkDuplicateDefinitionInParameterList(FormalParameterList node) {
    Map<String, Element> definedNames = new HashMap<String, Element>();
    for (FormalParameter parameter in node.parameters) {
      SimpleIdentifier identifier = parameter.identifier;
      if (identifier != null) {
        // The identifier can be null if this is a parameter list for a generic
        // function type.
        _checkDuplicateIdentifier(definedNames, identifier);
      }
    }
  }

  /**
   * Check that all of the parameters have unique names.
   */
  void _checkDuplicateDefinitionInTypeParameterList(TypeParameterList node) {
    Map<String, Element> definedNames = new HashMap<String, Element>();
    for (TypeParameter parameter in node.typeParameters) {
      _checkDuplicateIdentifier(definedNames, parameter.name);
    }
  }

  /**
   * Check that there are no members with the same name.
   */
  void _checkDuplicateEnumMembers(EnumDeclaration node) {
    ClassElement element = node.declaredElement;

    Map<String, Element> instanceGetters = new HashMap<String, Element>();
    Map<String, Element> staticGetters = new HashMap<String, Element>();

    String indexName = 'index';
    String valuesName = 'values';
    instanceGetters[indexName] = element.getGetter(indexName);
    staticGetters[valuesName] = element.getGetter(valuesName);

    for (EnumConstantDeclaration constant in node.constants) {
      _checkDuplicateIdentifier(staticGetters, constant.name);
    }

    for (EnumConstantDeclaration constant in node.constants) {
      SimpleIdentifier identifier = constant.name;
      String name = identifier.name;
      if (instanceGetters.containsKey(name)) {
        String enumName = element.displayName;
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.CONFLICTING_STATIC_AND_INSTANCE,
            identifier,
            [enumName, name, enumName]);
      }
    }
  }

  /**
   * Check whether the given [element] defined by the [identifier] is already
   * in one of the scopes - [getterScope] or [setterScope], and produce an
   * error if it is.
   */
  void _checkDuplicateIdentifier(
      Map<String, Element> getterScope, SimpleIdentifier identifier,
      {Element element, Map<String, Element> setterScope}) {
    element ??= identifier.staticElement;

    // Fields define getters and setters, so check them separately.
    if (element is PropertyInducingElement) {
      _checkDuplicateIdentifier(getterScope, identifier,
          element: element.getter, setterScope: setterScope);
      if (!element.isConst && !element.isFinal) {
        _checkDuplicateIdentifier(getterScope, identifier,
            element: element.setter, setterScope: setterScope);
      }
      return;
    }

    ErrorCode getError(Element previous, Element current) {
      if (previous is PrefixElement) {
        return CompileTimeErrorCode.PREFIX_COLLIDES_WITH_TOP_LEVEL_MEMBER;
      }
      return CompileTimeErrorCode.DUPLICATE_DEFINITION;
    }

    bool isGetterSetterPair(Element a, Element b) {
      if (a is PropertyAccessorElement && b is PropertyAccessorElement) {
        return a.isGetter && b.isSetter || a.isSetter && b.isGetter;
      }
      return false;
    }

    String name = identifier.name;
    if (element is MethodElement && element.isOperator && name == '-') {
      if (element.parameters.length == 0) {
        name = 'unary-';
      }
    }

    Element previous = getterScope[name];
    if (previous != null) {
      if (isGetterSetterPair(element, previous)) {
        // OK
      } else {
        _errorReporter.reportErrorForNode(
          getError(previous, element),
          identifier,
          [name],
        );
      }
    } else {
      getterScope[name] = element;
    }

    if (element is PropertyAccessorElement && element.isSetter) {
      previous = setterScope[name];
      if (previous != null) {
        _errorReporter.reportErrorForNode(
          getError(previous, element),
          identifier,
          [name],
        );
      } else {
        setterScope[name] = element;
      }
    }
  }

  /**
   * Check that there are no members with the same name.
   */
  void _checkDuplicateUnitMembers(CompilationUnit node) {
    Map<String, Element> definedGetters = new HashMap<String, Element>();
    Map<String, Element> definedSetters = new HashMap<String, Element>();

    void addWithoutChecking(CompilationUnitElement element) {
      for (PropertyAccessorElement accessor in element.accessors) {
        String name = accessor.name;
        if (accessor.isSetter) {
          name += '=';
        }
        definedGetters[name] = accessor;
      }
      for (ClassElement type in element.enums) {
        definedGetters[type.name] = type;
      }
      for (FunctionElement function in element.functions) {
        definedGetters[function.name] = function;
      }
      for (FunctionTypeAliasElement alias in element.functionTypeAliases) {
        definedGetters[alias.name] = alias;
      }
      for (TopLevelVariableElement variable in element.topLevelVariables) {
        definedGetters[variable.name] = variable;
        if (!variable.isFinal && !variable.isConst) {
          definedGetters[variable.name + '='] = variable;
        }
      }
      for (ClassElement type in element.types) {
        definedGetters[type.name] = type;
      }
    }

    for (ImportElement importElement in _currentLibrary.imports) {
      PrefixElement prefix = importElement.prefix;
      if (prefix != null) {
        definedGetters[prefix.name] = prefix;
      }
    }
    CompilationUnitElement element = node.declaredElement;
    if (element != _currentLibrary.definingCompilationUnit) {
      addWithoutChecking(_currentLibrary.definingCompilationUnit);
      for (CompilationUnitElement part in _currentLibrary.parts) {
        if (element == part) {
          break;
        }
        addWithoutChecking(part);
      }
    }
    for (CompilationUnitMember member in node.declarations) {
      if (member is NamedCompilationUnitMember) {
        _checkDuplicateIdentifier(definedGetters, member.name,
            setterScope: definedSetters);
      } else if (member is TopLevelVariableDeclaration) {
        for (VariableDeclaration variable in member.variables.variables) {
          _checkDuplicateIdentifier(definedGetters, variable.name,
              setterScope: definedSetters);
        }
      }
    }
  }

  /**
   * Check that the given list of variable declarations does not define multiple
   * variables of the same name.
   */
  void _checkDuplicateVariables(VariableDeclarationList node) {
    Map<String, Element> definedNames = new HashMap<String, Element>();
    for (VariableDeclaration variable in node.variables) {
      _checkDuplicateIdentifier(definedNames, variable.name);
    }
  }

  /**
   * Check that return statements without expressions are not in a generative
   * constructor and the return type is not assignable to `null`; that is, we
   * don't have `return;` if the enclosing method has a non-void containing
   * return type.
   *
   * See [CompileTimeErrorCode.RETURN_IN_GENERATIVE_CONSTRUCTOR],
   * [StaticWarningCode.RETURN_WITHOUT_VALUE], and
   * [StaticTypeWarningCode.RETURN_OF_INVALID_TYPE].
   */
  void _checkForAllEmptyReturnStatementErrorCodes(
      ReturnStatement statement, DartType expectedReturnType) {
    if (_inGenerator) {
      return;
    }
    var returnType =
        _inAsync ? _typeSystem.flatten(expectedReturnType) : expectedReturnType;
    if (returnType.isDynamic ||
        returnType.isDartCoreNull ||
        returnType.isVoid) {
      return;
    }
    // If we reach here, this is an invalid return
    _hasReturnWithoutValue = true;
    _errorReporter.reportErrorForNode(
        StaticWarningCode.RETURN_WITHOUT_VALUE, statement);
    return;
  }

  /**
   * Verify that the given [constructor] declaration does not violate any of the
   * error codes relating to the initialization of fields in the enclosing
   * class.
   *
   * See [_initialFieldElementsMap],
   * [StaticWarningCode.FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR], and
   * [CompileTimeErrorCode.FINAL_INITIALIZED_MULTIPLE_TIMES].
   */
  void _checkForAllFinalInitializedErrorCodes(
      ConstructorDeclaration constructor) {
    if (constructor.factoryKeyword != null ||
        constructor.redirectedConstructor != null ||
        constructor.externalKeyword != null) {
      return;
    }
    // Ignore if native class.
    if (_isInNativeClass) {
      return;
    }

    Map<FieldElement, INIT_STATE> fieldElementsMap =
        new HashMap<FieldElement, INIT_STATE>.from(_initialFieldElementsMap);
    // Visit all of the field formal parameters
    NodeList<FormalParameter> formalParameters =
        constructor.parameters.parameters;
    for (FormalParameter formalParameter in formalParameters) {
      FormalParameter baseParameter(FormalParameter parameter) {
        if (parameter is DefaultFormalParameter) {
          return parameter.parameter;
        }
        return parameter;
      }

      FormalParameter parameter = baseParameter(formalParameter);
      if (parameter is FieldFormalParameter) {
        FieldElement fieldElement =
            (parameter.declaredElement as FieldFormalParameterElementImpl)
                .field;
        INIT_STATE state = fieldElementsMap[fieldElement];
        if (state == INIT_STATE.NOT_INIT) {
          fieldElementsMap[fieldElement] = INIT_STATE.INIT_IN_FIELD_FORMAL;
        } else if (state == INIT_STATE.INIT_IN_DECLARATION) {
          if (fieldElement.isFinal || fieldElement.isConst) {
            _errorReporter.reportErrorForNode(
                StaticWarningCode
                    .FINAL_INITIALIZED_IN_DECLARATION_AND_CONSTRUCTOR,
                formalParameter.identifier,
                [fieldElement.displayName]);
          }
        } else if (state == INIT_STATE.INIT_IN_FIELD_FORMAL) {
          if (fieldElement.isFinal || fieldElement.isConst) {
            _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.FINAL_INITIALIZED_MULTIPLE_TIMES,
                formalParameter.identifier,
                [fieldElement.displayName]);
          }
        }
      }
    }
    // Visit all of the initializers
    NodeList<ConstructorInitializer> initializers = constructor.initializers;
    for (ConstructorInitializer constructorInitializer in initializers) {
      if (constructorInitializer is RedirectingConstructorInvocation) {
        return;
      }
      if (constructorInitializer is ConstructorFieldInitializer) {
        SimpleIdentifier fieldName = constructorInitializer.fieldName;
        Element element = fieldName.staticElement;
        if (element is FieldElement) {
          INIT_STATE state = fieldElementsMap[element];
          if (state == INIT_STATE.NOT_INIT) {
            fieldElementsMap[element] = INIT_STATE.INIT_IN_INITIALIZERS;
          } else if (state == INIT_STATE.INIT_IN_DECLARATION) {
            if (element.isFinal || element.isConst) {
              _errorReporter.reportErrorForNode(
                  StaticWarningCode
                      .FIELD_INITIALIZED_IN_INITIALIZER_AND_DECLARATION,
                  fieldName);
            }
          } else if (state == INIT_STATE.INIT_IN_FIELD_FORMAL) {
            _errorReporter.reportErrorForNode(
                CompileTimeErrorCode
                    .FIELD_INITIALIZED_IN_PARAMETER_AND_INITIALIZER,
                fieldName);
          } else if (state == INIT_STATE.INIT_IN_INITIALIZERS) {
            _errorReporter.reportErrorForNode(
                CompileTimeErrorCode.FIELD_INITIALIZED_BY_MULTIPLE_INITIALIZERS,
                fieldName,
                [element.displayName]);
          }
        }
      }
    }
    // Prepare a list of not initialized fields.
    List<FieldElement> notInitFinalFields = <FieldElement>[];
    fieldElementsMap.forEach((FieldElement fieldElement, INIT_STATE state) {
      if (state == INIT_STATE.NOT_INIT) {
        if (fieldElement.isFinal) {
          notInitFinalFields.add(fieldElement);
        }
      }
    });
    // Visit all of the states in the map to ensure that none were never
    // initialized.
    fieldElementsMap.forEach((FieldElement fieldElement, INIT_STATE state) {
      if (state == INIT_STATE.NOT_INIT) {
        if (fieldElement.isConst) {
          _errorReporter.reportErrorForNode(
              CompileTimeErrorCode.CONST_NOT_INITIALIZED,
              constructor.returnType,
              [fieldElement.name]);
        }
      }
    });

    if (notInitFinalFields.isNotEmpty) {
      List<String> names = notInitFinalFields.map((item) => item.name).toList();
      names.sort();
      if (names.length == 1) {
        _errorReporter.reportErrorForNode(
            StaticWarningCode.FINAL_NOT_INITIALIZED_CONSTRUCTOR_1,
            constructor.returnType,
            names);
      } else if (names.length == 2) {
        _errorReporter.reportErrorForNode(
            StaticWarningCode.FINAL_NOT_INITIALIZED_CONSTRUCTOR_2,
            constructor.returnType,
            names);
      } else {
        _errorReporter.reportErrorForNode(
            StaticWarningCode.FINAL_NOT_INITIALIZED_CONSTRUCTOR_3_PLUS,
            constructor.returnType,
            [names[0], names[1], names.length - 2]);
      }
    }
  }

  /**
   * Verify that all classes of the given [withClause] are valid.
   *
   * See [CompileTimeErrorCode.MIXIN_CLASS_DECLARES_CONSTRUCTOR],
   * [CompileTimeErrorCode.MIXIN_INHERITS_FROM_NOT_OBJECT], and
   * [CompileTimeErrorCode.MIXIN_REFERENCES_SUPER].
   */
  bool _checkForAllMixinErrorCodes(WithClause withClause) {
    if (withClause == null) {
      return false;
    }
    bool problemReported = false;
    int mixinTypeIndex = -1;
    for (int mixinNameIndex = 0;
        mixinNameIndex < withClause.mixinTypes.length;
        mixinNameIndex++) {
      TypeName mixinName = withClause.mixinTypes[mixinNameIndex];
      DartType mixinType = mixinName.type;
      if (mixinType is InterfaceType) {
        mixinTypeIndex++;
        if (_checkForExtendsOrImplementsDisallowedClass(
            mixinName, CompileTimeErrorCode.MIXIN_OF_DISALLOWED_CLASS)) {
          problemReported = true;
        } else {
          ClassElement mixinElement = mixinType.element;
          if (_checkForExtendsOrImplementsDeferredClass(
              mixinName, CompileTimeErrorCode.MIXIN_DEFERRED_CLASS)) {
            problemReported = true;
          }
          if (mixinElement.isMixin) {
            if (_checkForMixinSuperclassConstraints(
                mixinNameIndex, mixinName)) {
              problemReported = true;
            } else if (_checkForMixinSuperInvokedMembers(
                mixinTypeIndex, mixinName, mixinElement, mixinType)) {
              problemReported = true;
            }
          } else {
            if (_checkForMixinClassDeclaresConstructor(
                mixinName, mixinElement)) {
              problemReported = true;
            }
            if (_checkForMixinInheritsNotFromObject(mixinName, mixinElement)) {
              problemReported = true;
            }
            if (_checkForMixinReferencesSuper(mixinName, mixinElement)) {
              problemReported = true;
            }
          }
        }
      }
    }
    return problemReported;
  }

  /**
   * Check for errors related to the redirected constructors.
   *
   * See [StaticWarningCode.REDIRECT_TO_INVALID_RETURN_TYPE],
   * [StaticWarningCode.REDIRECT_TO_INVALID_FUNCTION_TYPE], and
   * [StaticWarningCode.REDIRECT_TO_MISSING_CONSTRUCTOR].
   */
  void _checkForAllRedirectConstructorErrorCodes(
      ConstructorDeclaration declaration) {
    // Prepare redirected constructor node
    ConstructorName redirectedConstructor = declaration.redirectedConstructor;
    if (redirectedConstructor == null) {
      return;
    }

    // Prepare redirected constructor type
    ConstructorElement redirectedElement = redirectedConstructor.staticElement;
    if (redirectedElement == null) {
      // If the element is null, we check for the
      // REDIRECT_TO_MISSING_CONSTRUCTOR case
      TypeName constructorTypeName = redirectedConstructor.type;
      DartType redirectedType = constructorTypeName.type;
      if (redirectedType != null &&
          redirectedType.element != null &&
          !redirectedType.isDynamic) {
        // Prepare the constructor name
        String constructorStrName = constructorTypeName.name.name;
        if (redirectedConstructor.name != null) {
          constructorStrName += ".${redirectedConstructor.name.name}";
        }
        ErrorCode errorCode = (declaration.constKeyword != null
            ? CompileTimeErrorCode.REDIRECT_TO_MISSING_CONSTRUCTOR
            : StaticWarningCode.REDIRECT_TO_MISSING_CONSTRUCTOR);
        _errorReporter.reportErrorForNode(errorCode, redirectedConstructor,
            [constructorStrName, redirectedType.displayName]);
      }
      return;
    }
    FunctionType redirectedType = redirectedElement.type;
    DartType redirectedReturnType = redirectedType.returnType;

    // Report specific problem when return type is incompatible
    FunctionType constructorType =
        resolutionMap.elementDeclaredByConstructorDeclaration(declaration).type;
    DartType constructorReturnType = constructorType.returnType;
    if (!_typeSystem.isAssignableTo(
        redirectedReturnType, constructorReturnType)) {
      _errorReporter.reportErrorForNode(
          StaticWarningCode.REDIRECT_TO_INVALID_RETURN_TYPE,
          redirectedConstructor,
          [redirectedReturnType, constructorReturnType]);
      return;
    } else if (!_typeSystem.isSubtypeOf(redirectedType, constructorType)) {
      // Check parameters.
      _errorReporter.reportErrorForNode(
          StaticWarningCode.REDIRECT_TO_INVALID_FUNCTION_TYPE,
          redirectedConstructor,
          [redirectedType, constructorType]);
    }
  }

  /**
   * Check that the return [statement] of the form <i>return e;</i> is not in a
   * generative constructor.
   *
   * Check that return statements without expressions are not in a generative
   * constructor and the return type is not assignable to `null`; that is, we
   * don't have `return;` if the enclosing method has a non-void containing
   * return type.
   *
   * Check that the return type matches the type of the declared return type in
   * the enclosing method or function.
   *
   * See [CompileTimeErrorCode.RETURN_IN_GENERATIVE_CONSTRUCTOR],
   * [StaticWarningCode.RETURN_WITHOUT_VALUE], and
   * [StaticTypeWarningCode.RETURN_OF_INVALID_TYPE].
   */
  void _checkForAllReturnStatementErrorCodes(ReturnStatement statement) {
    FunctionType functionType = _enclosingFunction?.type;
    DartType expectedReturnType = functionType == null
        ? DynamicTypeImpl.instance
        : functionType.returnType;
    Expression returnExpression = statement.expression;

    // RETURN_IN_GENERATIVE_CONSTRUCTOR
    bool isGenerativeConstructor(ExecutableElement element) =>
        element is ConstructorElement && !element.isFactory;
    if (isGenerativeConstructor(_enclosingFunction)) {
      if (returnExpression == null) {
        return;
      }
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.RETURN_IN_GENERATIVE_CONSTRUCTOR,
          returnExpression);
      return;
    }
    // RETURN_WITHOUT_VALUE
    if (returnExpression == null) {
      _checkForAllEmptyReturnStatementErrorCodes(statement, expectedReturnType);
      return;
    } else if (_inGenerator) {
      // RETURN_IN_GENERATOR
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.RETURN_IN_GENERATOR,
          statement,
          [_inAsync ? "async*" : "sync*"]);
      return;
    }

    _checkForReturnOfInvalidType(returnExpression, expectedReturnType);
  }

  /**
   * Verify that the export namespace of the given export [directive] does not
   * export any name already exported by another export directive. The
   * [exportElement] is the [ExportElement] retrieved from the node. If the
   * element in the node was `null`, then this method is not called. The
   * [exportedLibrary] is the library element containing the exported element.
   *
   * See [CompileTimeErrorCode.AMBIGUOUS_EXPORT].
   */
  void _checkForAmbiguousExport(ExportDirective directive,
      ExportElement exportElement, LibraryElement exportedLibrary) {
    if (exportedLibrary == null) {
      return;
    }
    // check exported names
    Namespace namespace =
        new NamespaceBuilder().createExportNamespaceForDirective(exportElement);
    Map<String, Element> definedNames = namespace.definedNames;
    for (String name in definedNames.keys) {
      Element element = definedNames[name];
      Element prevElement = _exportedElements[name];
      if (element != null && prevElement != null && prevElement != element) {
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.AMBIGUOUS_EXPORT, directive, [
          name,
          prevElement.library.definingCompilationUnit.source.uri,
          element.library.definingCompilationUnit.source.uri
        ]);
        return;
      } else {
        _exportedElements[name] = element;
      }
    }
  }

  /**
   * Check the given node to see whether it was ambiguous because the name was
   * imported from two or more imports.
   */
  void _checkForAmbiguousImport(SimpleIdentifier node) {
    Element element = node.staticElement;
    if (element is MultiplyDefinedElementImpl) {
      String name = element.displayName;
      List<Element> conflictingMembers = element.conflictingElements;
      int count = conflictingMembers.length;
      List<String> libraryNames = new List<String>(count);
      for (int i = 0; i < count; i++) {
        libraryNames[i] = _getLibraryName(conflictingMembers[i]);
      }
      libraryNames.sort();
      _errorReporter.reportErrorForNode(StaticWarningCode.AMBIGUOUS_IMPORT,
          node, [name, StringUtilities.printListOfQuotedNames(libraryNames)]);
    }
  }

  /**
   * Verify that the given [expression] can be assigned to its corresponding
   * parameters. The [expectedStaticType] is the expected static type of the
   * parameter. The [actualStaticType] is the actual static type of the
   * argument.
   */
  void _checkForArgumentTypeNotAssignable(
      Expression expression,
      DartType expectedStaticType,
      DartType actualStaticType,
      ErrorCode errorCode) {
    // Warning case: test static type information
    if (actualStaticType != null && expectedStaticType != null) {
      if (!expectedStaticType.isVoid && _checkForUseOfVoidResult(expression)) {
        return;
      }

      _checkForAssignableExpressionAtType(
          expression, actualStaticType, expectedStaticType, errorCode);
    }
  }

  /**
   * Verify that the given [argument] can be assigned to its corresponding
   * parameter.
   *
   * This method corresponds to
   * [BestPracticesVerifier.checkForArgumentTypeNotAssignableForArgument].
   *
   * See [StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE].
   */
  void _checkForArgumentTypeNotAssignableForArgument(Expression argument) {
    if (argument == null) {
      return;
    }

    ParameterElement staticParameterElement = argument.staticParameterElement;
    DartType staticParameterType = staticParameterElement?.type;
    _checkForArgumentTypeNotAssignableWithExpectedTypes(argument,
        staticParameterType, StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE);
  }

  /**
   * Verify that the given [expression] can be assigned to its corresponding
   * parameters. The [expectedStaticType] is the expected static type.
   *
   * This method corresponds to
   * [BestPracticesVerifier.checkForArgumentTypeNotAssignableWithExpectedTypes].
   *
   * See [StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE],
   * [CompileTimeErrorCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE],
   * [StaticWarningCode.LIST_ELEMENT_TYPE_NOT_ASSIGNABLE],
   * [CompileTimeErrorCode.MAP_KEY_TYPE_NOT_ASSIGNABLE],
   * [CompileTimeErrorCode.MAP_VALUE_TYPE_NOT_ASSIGNABLE],
   * [StaticWarningCode.MAP_KEY_TYPE_NOT_ASSIGNABLE], and
   * [StaticWarningCode.MAP_VALUE_TYPE_NOT_ASSIGNABLE].
   */
  void _checkForArgumentTypeNotAssignableWithExpectedTypes(
      Expression expression, DartType expectedStaticType, ErrorCode errorCode) {
    _checkForArgumentTypeNotAssignable(
        expression, expectedStaticType, getStaticType(expression), errorCode);
  }

  /**
   * Verify that the arguments in the given [argumentList] can be assigned to
   * their corresponding parameters.
   *
   * This method corresponds to
   * [BestPracticesVerifier.checkForArgumentTypesNotAssignableInList].
   *
   * See [StaticWarningCode.ARGUMENT_TYPE_NOT_ASSIGNABLE].
   */
  void _checkForArgumentTypesNotAssignableInList(ArgumentList argumentList) {
    if (argumentList == null) {
      return;
    }

    for (Expression argument in argumentList.arguments) {
      _checkForArgumentTypeNotAssignableForArgument(argument);
    }
  }

  /**
   * Check that the static type of the given expression is assignable to the
   * given type. If it isn't, report an error with the given error code. The
   * [type] is the type that the expression must be assignable to. The
   * [errorCode] is the error code to be reported. The [arguments] are the
   * arguments to pass in when creating the error.
   */
  void _checkForAssignability(Expression expression, InterfaceType type,
      ErrorCode errorCode, List<Object> arguments) {
    if (expression == null) {
      return;
    }
    DartType expressionType = expression.staticType;
    if (expressionType == null) {
      return;
    }
    if (_typeSystem.isAssignableTo(expressionType, type)) {
      return;
    }
    _errorReporter.reportErrorForNode(errorCode, expression, arguments);
  }

  bool _checkForAssignableExpression(
      Expression expression, DartType expectedStaticType, ErrorCode errorCode) {
    DartType actualStaticType = getStaticType(expression);
    return actualStaticType != null &&
        _checkForAssignableExpressionAtType(
            expression, actualStaticType, expectedStaticType, errorCode);
  }

  bool _checkForAssignableExpressionAtType(
      Expression expression,
      DartType actualStaticType,
      DartType expectedStaticType,
      ErrorCode errorCode) {
    if (!_typeSystem.isAssignableTo(actualStaticType, expectedStaticType)) {
      _errorReporter.reportTypeErrorForNode(
          errorCode, expression, [actualStaticType, expectedStaticType]);
      return false;
    }
    return true;
  }

  /**
   * Verify that the given [expression] is not final.
   *
   * See [StaticWarningCode.ASSIGNMENT_TO_CONST],
   * [StaticWarningCode.ASSIGNMENT_TO_FINAL], and
   * [StaticWarningCode.ASSIGNMENT_TO_METHOD].
   */
  void _checkForAssignmentToFinal(Expression expression) {
    // prepare element
    Element element = null;
    AstNode highlightedNode = expression;
    if (expression is Identifier) {
      element = expression.staticElement;
      if (expression is PrefixedIdentifier) {
        highlightedNode = expression.identifier;
      }
    } else if (expression is PropertyAccess) {
      element = expression.propertyName.staticElement;
      highlightedNode = expression.propertyName;
    }
    // check if element is assignable
    Element toVariable(Element element) {
      return element is PropertyAccessorElement ? element.variable : element;
    }

    element = toVariable(element);
    if (element is VariableElement) {
      if (element.isConst) {
        _errorReporter.reportErrorForNode(
            StaticWarningCode.ASSIGNMENT_TO_CONST, expression);
      } else if (element.isFinal) {
        if (element is FieldElementImpl) {
          if (element.setter == null && element.isSynthetic) {
            _errorReporter.reportErrorForNode(
                StaticWarningCode.ASSIGNMENT_TO_FINAL_NO_SETTER,
                highlightedNode,
                [element.name, element.enclosingElement.displayName]);
          } else {
            _errorReporter.reportErrorForNode(
                StaticWarningCode.ASSIGNMENT_TO_FINAL,
                highlightedNode,
                [element.name]);
          }
          return;
        }
        _errorReporter.reportErrorForNode(
            StaticWarningCode.ASSIGNMENT_TO_FINAL_LOCAL,
            highlightedNode,
            [element.name]);
      }
    } else if (element is FunctionElement) {
      _errorReporter.reportErrorForNode(
          StaticWarningCode.ASSIGNMENT_TO_FUNCTION, expression);
    } else if (element is MethodElement) {
      _errorReporter.reportErrorForNode(
          StaticWarningCode.ASSIGNMENT_TO_METHOD, expression);
    } else if (element is ClassElement ||
        element is FunctionTypeAliasElement ||
        element is TypeParameterElement) {
      _errorReporter.reportErrorForNode(
          StaticWarningCode.ASSIGNMENT_TO_TYPE, expression);
    }
  }

  /**
   * Verifies that the class is not named `Function` and that it doesn't
   * extends/implements/mixes in `Function`.
   */
  void _checkForBadFunctionUse(ClassDeclaration node) {
    ExtendsClause extendsClause = node.extendsClause;
    WithClause withClause = node.withClause;

    if (node.name.name == "Function") {
      _errorReporter.reportErrorForNode(
          HintCode.DEPRECATED_FUNCTION_CLASS_DECLARATION, node.name);
    }

    if (extendsClause != null) {
      InterfaceType superclassType = _enclosingClass.supertype;
      ClassElement superclassElement = superclassType?.element;
      if (superclassElement != null && superclassElement.name == "Function") {
        _errorReporter.reportErrorForNode(
            HintCode.DEPRECATED_EXTENDS_FUNCTION, extendsClause.superclass);
      }
    }

    if (withClause != null) {
      for (TypeName type in withClause.mixinTypes) {
        Element mixinElement = type.name.staticElement;
        if (mixinElement != null && mixinElement.name == "Function") {
          _errorReporter.reportErrorForNode(
              HintCode.DEPRECATED_MIXIN_FUNCTION, type);
        }
      }
    }
  }

  /**
   * Verify that the given [identifier] is not a keyword, and generates the
   * given [errorCode] on the identifier if it is a keyword.
   *
   * See [CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE_NAME],
   * [CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE_PARAMETER_NAME], and
   * [CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPEDEF_NAME].
   */
  void _checkForBuiltInIdentifierAsName(
      SimpleIdentifier identifier, ErrorCode errorCode) {
    Token token = identifier.token;
    if (token.type.isKeyword && token.keyword?.isPseudo != true) {
      _errorReporter
          .reportErrorForNode(errorCode, identifier, [identifier.name]);
    }
  }

  /**
   * Verify that the given [switchCase] is terminated with 'break', 'continue',
   * 'return' or 'throw'.
   *
   * see [StaticWarningCode.CASE_BLOCK_NOT_TERMINATED].
   */
  void _checkForCaseBlockNotTerminated(SwitchCase switchCase) {
    NodeList<Statement> statements = switchCase.statements;
    if (statements.isEmpty) {
      // fall-through without statements at all
      AstNode parent = switchCase.parent;
      if (parent is SwitchStatement) {
        NodeList<SwitchMember> members = parent.members;
        int index = members.indexOf(switchCase);
        if (index != -1 && index < members.length - 1) {
          return;
        }
      }
      // no other switch member after this one
    } else {
      Statement statement = statements.last;
      if (statement is Block && statement.statements.isNotEmpty) {
        Block block = statement;
        statement = block.statements.last;
      }
      // terminated with statement
      if (statement is BreakStatement ||
          statement is ContinueStatement ||
          statement is ReturnStatement) {
        return;
      }
      // terminated with 'throw' expression
      if (statement is ExpressionStatement) {
        Expression expression = statement.expression;
        if (expression is ThrowExpression || expression is RethrowExpression) {
          return;
        }
      }
    }

    _errorReporter.reportErrorForToken(
        StaticWarningCode.CASE_BLOCK_NOT_TERMINATED, switchCase.keyword);
  }

  /**
   * Verify that the switch cases in the given switch [statement] are terminated
   * with 'break', 'continue', 'rethrow', 'return' or 'throw'.
   *
   * See [StaticWarningCode.CASE_BLOCK_NOT_TERMINATED].
   */
  void _checkForCaseBlocksNotTerminated(SwitchStatement statement) {
    NodeList<SwitchMember> members = statement.members;
    int lastMember = members.length - 1;
    for (int i = 0; i < lastMember; i++) {
      SwitchMember member = members[i];
      if (member is SwitchCase) {
        _checkForCaseBlockNotTerminated(member);
      }
    }
  }

  /**
   * Verify that the [_enclosingClass] does not have a method and getter pair
   * with the same name on, via inheritance.
   *
   * See [CompileTimeErrorCode.CONFLICTING_STATIC_AND_INSTANCE],
   * [CompileTimeErrorCode.CONFLICTING_METHOD_AND_FIELD], and
   * [CompileTimeErrorCode.CONFLICTING_FIELD_AND_METHOD].
   */
  void _checkForConflictingClassMembers() {
    if (_enclosingClass == null) {
      return;
    }
    InterfaceType enclosingType = _enclosingClass.type;
    Uri libraryUri = _currentLibrary.source.uri;

    // method declared in the enclosing class vs. inherited getter/setter
    for (MethodElement method in _enclosingClass.methods) {
      String name = method.name;

      // find inherited property accessor
      ExecutableElement inherited = _inheritanceManager
          .getInherited(enclosingType, new Name(libraryUri, name))
          ?.element;
      inherited ??= _inheritanceManager
          .getInherited(enclosingType, new Name(libraryUri, '$name='))
          ?.element;

      if (method.isStatic && inherited != null) {
        _errorReporter.reportErrorForElement(
            CompileTimeErrorCode.CONFLICTING_STATIC_AND_INSTANCE, method, [
          _enclosingClass.displayName,
          name,
          inherited.enclosingElement.displayName,
        ]);
      } else if (inherited is PropertyAccessorElement) {
        _errorReporter.reportErrorForElement(
            CompileTimeErrorCode.CONFLICTING_METHOD_AND_FIELD, method, [
          _enclosingClass.displayName,
          inherited.enclosingElement.displayName,
          name
        ]);
      }
    }

    // getter declared in the enclosing class vs. inherited method
    for (PropertyAccessorElement accessor in _enclosingClass.accessors) {
      String name = accessor.displayName;

      // find inherited method or property accessor
      ExecutableElement inherited = _inheritanceManager
          .getInherited(enclosingType, new Name(libraryUri, name))
          ?.element;
      inherited ??= _inheritanceManager
          .getInherited(enclosingType, new Name(libraryUri, '$name='))
          ?.element;

      if (accessor.isStatic && inherited != null) {
        _errorReporter.reportErrorForElement(
            CompileTimeErrorCode.CONFLICTING_STATIC_AND_INSTANCE, accessor, [
          _enclosingClass.displayName,
          name,
          inherited.enclosingElement.displayName,
        ]);
      } else if (inherited is MethodElement) {
        _errorReporter.reportErrorForElement(
            CompileTimeErrorCode.CONFLICTING_FIELD_AND_METHOD, accessor, [
          _enclosingClass.displayName,
          name,
          inherited.enclosingElement.displayName
        ]);
      }
    }
  }

  void _checkForConflictingGenerics(NamedCompilationUnitMember node) {
    var visitedClasses = <ClassElement>[];
    var interfaces = <ClassElement, InterfaceType>{};
    void visit(InterfaceType type) {
      if (type == null) return;
      var element = type.element;
      if (visitedClasses.contains(element)) return;
      visitedClasses.add(element);
      if (element.typeParameters.isNotEmpty) {
        var oldType = interfaces[element];
        if (oldType == null) {
          interfaces[element] = type;
        } else if (!oldType.isEquivalentTo(type)) {
          _errorReporter.reportErrorForNode(
              CompileTimeErrorCode.CONFLICTING_GENERIC_INTERFACES,
              node,
              [_enclosingClass.name, oldType, type]);
        }
      }
      visit(type.superclass);
      type.mixins.forEach(visit);
      type.superclassConstraints.forEach(visit);
      type.interfaces.forEach(visit);
      visitedClasses.removeLast();
    }

    visit(_enclosingClass.type);
  }

  /**
   * Verify all conflicts between type variable and enclosing class.
   * TODO(scheglov)
   *
   * See [CompileTimeErrorCode.CONFLICTING_TYPE_VARIABLE_AND_CLASS], and
   * [CompileTimeErrorCode.CONFLICTING_TYPE_VARIABLE_AND_MEMBER].
   */
  void _checkForConflictingTypeVariableErrorCodes() {
    for (TypeParameterElement typeParameter in _enclosingClass.typeParameters) {
      String name = typeParameter.name;
      // name is same as the name of the enclosing class
      if (_enclosingClass.name == name) {
        _errorReporter.reportErrorForElement(
            CompileTimeErrorCode.CONFLICTING_TYPE_VARIABLE_AND_CLASS,
            typeParameter,
            [name]);
      }
      // check members
      if (_enclosingClass.getMethod(name) != null ||
          _enclosingClass.getGetter(name) != null ||
          _enclosingClass.getSetter(name) != null) {
        _errorReporter.reportErrorForElement(
            CompileTimeErrorCode.CONFLICTING_TYPE_VARIABLE_AND_MEMBER,
            typeParameter,
            [name]);
      }
    }
  }

  /**
   * Verify that if the given [constructor] declaration is 'const' then there
   * are no invocations of non-'const' super constructors.
   *
   * See [CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_CONST_SUPER].
   */
  void _checkForConstConstructorWithNonConstSuper(
      ConstructorDeclaration constructor) {
    if (!_isEnclosingConstructorConst) {
      return;
    }
    // OK, const factory, checked elsewhere
    if (constructor.factoryKeyword != null) {
      return;
    }

    // check for mixins
    var hasInstanceField = false;
    for (var mixin in _enclosingClass.mixins) {
      var fields = mixin.element.fields;
      for (var i = 0; i < fields.length; ++i) {
        if (!fields[i].isStatic) {
          hasInstanceField = true;
          break;
        }
      }
    }
    if (hasInstanceField) {
      // TODO(scheglov) Provide the list of fields.
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_MIXIN_WITH_FIELD,
          constructor.returnType);
      return;
    }

    // try to find and check super constructor invocation
    for (ConstructorInitializer initializer in constructor.initializers) {
      if (initializer is SuperConstructorInvocation) {
        ConstructorElement element = initializer.staticElement;
        if (element == null || element.isConst) {
          return;
        }
        _errorReporter.reportErrorForNode(
            CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_CONST_SUPER,
            initializer,
            [element.enclosingElement.displayName]);
        return;
      }
    }
    // no explicit super constructor invocation, check default constructor
    InterfaceType supertype = _enclosingClass.supertype;
    if (supertype == null) {
      return;
    }
    if (supertype.isObject) {
      return;
    }
    ConstructorElement unnamedConstructor =
        supertype.element.unnamedConstructor;
    if (unnamedConstructor == null || unnamedConstructor.isConst) {
      return;
    }

    // default constructor is not 'const', report problem
    _errorReporter.reportErrorForNode(
        CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_CONST_SUPER,
        constructor.returnType,
        [supertype.displayName]);
  }

  /**
   * Verify that if the given [constructor] declaration is 'const' then there
   * are no non-final instance variable. The [constructorElement] is the
   * constructor element.
   *
   * See [CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_FINAL_FIELD].
   */
  void _checkForConstConstructorWithNonFinalField(
      ConstructorDeclaration constructor,
      ConstructorElement constructorElement) {
    if (!_isEnclosingConstructorConst) {
      return;
    }
    // check if there is non-final field
    ClassElement classElement = constructorElement.enclosingElement;
    if (!classElement.hasNonFinalField) {
      return;
    }

    _errorReporter.reportErrorForNode(
        CompileTimeErrorCode.CONST_CONSTRUCTOR_WITH_NON_FINAL_FIELD,
        constructor);
  }

  /**
   * Verify that the given 'const' instance creation [expression] is not
   * creating a deferred type. The [constructorName] is the constructor name,
   * always non-`null`. The [typeName] is the name of the type defining the
   * constructor, always non-`null`.
   *
   * See [CompileTimeErrorCode.CONST_DEFERRED_CLASS].
   */
  void _checkForConstDeferredClass(InstanceCreationExpression expression,
      ConstructorName constructorName, TypeName typeName) {
    if (typeName.isDeferred) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_DEFERRED_CLASS,
          constructorName,
          [typeName.name.name]);
    }
  }

  /**
   * Verify that the given throw [expression] is not enclosed in a 'const'
   * constructor declaration.
   *
   * See [CompileTimeErrorCode.CONST_CONSTRUCTOR_THROWS_EXCEPTION].
   */
  void _checkForConstEvalThrowsException(ThrowExpression expression) {
    if (_isEnclosingConstructorConst) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_CONSTRUCTOR_THROWS_EXCEPTION, expression);
    }
  }

  /**
   * Verify that the given normal formal [parameter] is not 'const'.
   *
   * See [CompileTimeErrorCode.CONST_FORMAL_PARAMETER].
   */
  void _checkForConstFormalParameter(NormalFormalParameter parameter) {
    if (parameter.isConst) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_FORMAL_PARAMETER, parameter);
    }
  }

  /**
   * Verify that the given instance creation [expression] is not being invoked
   * on an abstract class. The [typeName] is the [TypeName] of the
   * [ConstructorName] from the [InstanceCreationExpression], this is the AST
   * node that the error is attached to. The [type] is the type being
   * constructed with this [InstanceCreationExpression].
   *
   * See [StaticWarningCode.CONST_WITH_ABSTRACT_CLASS], and
   * [StaticWarningCode.NEW_WITH_ABSTRACT_CLASS].
   */
  void _checkForConstOrNewWithAbstractClass(
      InstanceCreationExpression expression,
      TypeName typeName,
      InterfaceType type) {
    if (type.element.isAbstract && !type.element.isMixin) {
      ConstructorElement element = expression.staticElement;
      if (element != null && !element.isFactory) {
        bool isImplicit =
            (expression as InstanceCreationExpressionImpl).isImplicit;
        if (!isImplicit) {
          _errorReporter.reportErrorForNode(
              expression.isConst
                  ? StaticWarningCode.CONST_WITH_ABSTRACT_CLASS
                  : StaticWarningCode.NEW_WITH_ABSTRACT_CLASS,
              typeName);
        } else {
          // TODO(brianwilkerson/jwren) Create a new different StaticWarningCode
          // which does not call out the new keyword so explicitly.
          _errorReporter.reportErrorForNode(
              StaticWarningCode.NEW_WITH_ABSTRACT_CLASS, typeName);
        }
      }
    }
  }

  /**
   * Verify that the given instance creation [expression] is not being invoked
   * on an enum. The [typeName] is the [TypeName] of the [ConstructorName] from
   * the [InstanceCreationExpression], this is the AST node that the error is
   * attached to. The [type] is the type being constructed with this
   * [InstanceCreationExpression].
   *
   * See [CompileTimeErrorCode.INSTANTIATE_ENUM].
   */
  void _checkForConstOrNewWithEnum(InstanceCreationExpression expression,
      TypeName typeName, InterfaceType type) {
    if (type.element.isEnum) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.INSTANTIATE_ENUM, typeName);
    }
  }

  /**
   * Verify that the given [expression] is not a mixin instantiation.
   */
  void _checkForConstOrNewWithMixin(InstanceCreationExpression expression,
      TypeName typeName, InterfaceType type) {
    if (type.element.isMixin) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.MIXIN_INSTANTIATE, typeName);
    }
  }

  /**
   * Verify that the given 'const' instance creation [expression] is not being
   * invoked on a constructor that is not 'const'.
   *
   * This method assumes that the instance creation was tested to be 'const'
   * before being called.
   *
   * See [CompileTimeErrorCode.CONST_WITH_NON_CONST].
   */
  void _checkForConstWithNonConst(InstanceCreationExpression expression) {
    ConstructorElement constructorElement = expression.staticElement;
    if (constructorElement != null && !constructorElement.isConst) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_WITH_NON_CONST, expression);
    }
  }

  /**
   * Verify that if the given 'const' instance creation [expression] is being
   * invoked on the resolved constructor. The [constructorName] is the
   * constructor name, always non-`null`. The [typeName] is the name of the type
   * defining the constructor, always non-`null`.
   *
   * This method assumes that the instance creation was tested to be 'const'
   * before being called.
   *
   * See [CompileTimeErrorCode.CONST_WITH_UNDEFINED_CONSTRUCTOR], and
   * [CompileTimeErrorCode.CONST_WITH_UNDEFINED_CONSTRUCTOR_DEFAULT].
   */
  void _checkForConstWithUndefinedConstructor(
      InstanceCreationExpression expression,
      ConstructorName constructorName,
      TypeName typeName) {
    // OK if resolved
    if (expression.staticElement != null) {
      return;
    }
    DartType type = typeName.type;
    if (type is InterfaceType) {
      ClassElement element = type.element;
      if (element != null && element.isEnum) {
        // We have already reported the error.
        return;
      }
    }
    Identifier className = typeName.name;
    // report as named or default constructor absence
    SimpleIdentifier name = constructorName.name;
    if (name != null) {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_WITH_UNDEFINED_CONSTRUCTOR,
          name,
          [className, name]);
    } else {
      _errorReporter.reportErrorForNode(
          CompileTimeErrorCode.CONST_WITH_UNDEFINED_CONSTRUCTOR_DEFAULT,
          constructorName,
          [className]);
    }
  }

  /**
   * Verify that there are no default parameters in the given function type
   * [alias].
   *
   * See [CompileTimeErrorCode.DEFAULT_VALUE_IN_FUNCTION_TYPE_ALIAS].
   */
  void _checkForDefaultValueInFunctionTypeAlias(FunctionTypeAlias alias) {
    FormalParameterList formalParameterList = alias.parameters;
    NodeList<FormalParameter> parameters = formalParameterList.parameters;
    for (FormalParameter parameter in parameters) {
      if (parameter is DefaultFormalParameter) {
        if (parameter.defaultValue != null) {
          _errorReporter.reportErrorForNode(
              CompileTimeErrorCode.DEFAULT_VALUE_IN_FUNCTION_TYPE_ALIAS, alias);
        }
      }
    }
  }

  /**
   * Verify that the given default formal [parameter] is not part of a function
   * typed parameter.
   *
   * See [CompileTimeErrorCode.DEFAULT_VALUE_IN_FUNCTION_TYPED_PARAMETER].
   */
  void _checkForDefaultValueInFunctionTypedParameter(
      DefaultFormalParameter parameter) {
    // OK, not in a function typed parameter.
    if (!_isInFunctionTypedFormalParameter) {
      return;
    }
    // OK, no default value.
    if (parameter.defaultValue == null) {
      return;
    }

    _errorReporter.reportErrorForNode(
        CompileTimeErrorCode.DEFAULT_VALUE_IN_FUNCTION_TYPED_PARAMETER,
        parameter);
  }

  /**
   * Verify that any deferred imports in the given compilation [unit] have a
   * unique prefix.
   *
   * See [CompileTimeErrorCode.SHARED_DEFERRED_PREFIX].
   */
  void _checkForDeferredPrefixCollisions(CompilationUnit unit) {
    NodeList<Directive> directives = unit.directives;
    int count = directives.length;
    if (count > 0) {
      Map<PrefixElement, List<ImportDirective>> prefixToDirectivesMap =
          new HashMap<PrefixElement, List<ImportDirective>>();
      for (int i = 0; i < count; i++) {
        Directive directive = directives[i];
        if (directive is ImportDirective) {
          SimpleIdentifier prefix = directive.prefix;
          if (prefix != null) {
            Element element = prefix.staticElement;
            if (element is PrefixElement) {
              List<ImportDirective> elements = prefixToDirectivesMap[element];
              if (elements == null) {
                elements = new List<ImportDirective>();
                prefixToDirectivesMap[element] = elements;
              }
              elements.add(directive);
            }
          }
        }
      }
      for (List<ImportDirective> imports in prefixToDirectivesMap.values) {
        _checkDeferredPrefixCollision(imports);
      }
    }
  }

  /**
   * Return `true` if the caller should continue checking the rest of the
   * information in the for-each part.
   */
  bool _checkForEachParts(ForEachParts node, SimpleIdentifier variable) {
    if (_checkForNullableDereference(node.iterable)) {
      return false;
    }

    if (_checkForUseOfVoidResult(node.iterable)) {
      return false;
    }

    DartType iterableType = getStaticType(node.iterable);
    if (iterableType.isDynamic) {
      return false;
    }

    // The type of the loop variable.
    DartType variableType = getStaticType(variable);

    AstNode parent = node.parent;
    Token awaitKeyword;
    if (parent is ForStatement) {
      awaitKeyword = parent.awaitKeyword;
    } else if (parent is ForElement) {
      awaitKeyword = parent.awaitKeyword;
    }
    DartType loopType = awaitKeyword != null
        ? _typeProvider.streamType
        : _typeProvider.iterableType;

    // Use an explicit string instead of [loopType] to remove the "<E>".
    String loopTypeName = awaitKeyword != null ? "Stream" : "Iterable";

    // The object being iterated has to implement Iterable<T> for some T that
    // is assignable to the variable's type.
    // TODO(rnystrom): Move this into mostSpecificTypeArgument()?
    iterableType = iterableType.resolveToBound(_typeProvider.objectType);
    DartType bestIterableType =
        _typeSystem.mostSpecificTypeArgument(iterableType, loopType);

    // Allow it to be a supertype of Iterable<T> (basically just Object) and do
    // an implicit downcast to Iterable<dynamic>.
    if (bestIterableType == null) {
      if (_typeSystem.isSubtypeOf(loopType, iterableType)) {
        bestIterableType = DynamicTypeImpl.instance;
      }
    }

    if (bestIterableType == null) {
      _errorReporter.reportTypeErrorForNode(
          StaticTypeWarningCode.FOR_IN_OF_INVALID_TYPE,
          node.iterable,
          [iterableType, loopTypeName]);
    } else if (!_typeSystem.isAssignableTo(bestIterableType, variableType)) {
      _errorReporter.reportTypeErrorForNode(
          StaticTypeWarningCode.FOR_IN_OF_INVALID_ELEMENT_TYPE,
          node.iterable,
          [iterableType, loopTypeName, variableType]);
    }
    return true;
  }

  /**
   * Verify that the given export [directive] has a unique name among other
   * exported libraries. The [exportElement] is the [ExportElement] retrieved
   * from the node, if the element in the node was `null`, then this method is
   * not called. The [exportedLibrary] is the library element containing the
   * exported element.
   *
   * See [CompileTimeErrorCode.EXPORT_DUPLICATED_LIBRARY_NAME].
   */
  void _checkForExportDuplicateLibraryName(ExportDirective directive,
      ExportElement exportElement, LibraryElement exportedLibrary) {
    if (exportedLibrary == null) {
      return;
    }
    String name = exportedLibrary.name;
    // check if there is other exported library with the same name
    LibraryElement prevLibrary = _nameToExportElement[name];
    if (prevLibrary != null) {
      if (prevLibrary != exportedLibrary) {
        if (!name.isEmpty) {
          _errorReporter.reportErrorForNode(
              StaticWarningCode.EXPORT_DUPLICATED_LIBRARY_NAMED, directive, [
            prevLibrary.definingCompilationUnit.source.uri.toString(),
            exportedLibrary.definingCompilationUnit.source.uri.toString(),
            name
          ]);
        }
        return;
      }
    } else {
      _nameToExportElement[name] = exportedLibrary;
    }
  }

  /**
   * Check that if the visiting library is not system, then any given library
   * should not be SDK internal library. The [exportElement] is the
   * [ExportElement] retrieved from the node, if the element in the node was
   * `null`, then this method is not called.
   *
   * See [CompileTimeErrorCode.EXPORT_INTERNAL_LIBRARY].
   */
  void _checkForExportInternalLibrary(
      ExportDirective directive, ExportElement exportElement) {
    if (_isInSystemLibrary) {
      return;
    }

    LibraryElement exportedLibrary = exportElement.exportedLibrary;
    if (exportedLibrary == null) {
      return;
    }

    // should be private
    DartSdk sdk = _currentLibrary.context.sourceFactory.dartSdk;
    String uri = exportedLibrary.source.uri.toString();
    SdkLibrary sdkLibrary = sdk.getSdkLibrary(uri);
    if (sdkLibrary == null) {
      return;
    }
    if (!sdkLibrary.isInternal) {
      return;
    }

    _errorReporter.reportErrorForNode(
        CompileTimeErrorCode.EXPORT_INTERNAL_LIBRARY,
        directive,
        [directive.uri]);
  }

  /**
   * Verify that the given extends [clause] does not extend a deferred class.
   *
   * See [CompileTimeErrorCode.EXTENDS_DEFERRED_CLASS].
   */
  void _checkForExtendsDeferredClass(TypeName superclass) {
    if (superclass == null) {
      return;
    }
    _checkForExtendsOrImplementsDeferredClass(
        superclass, CompileTimeErrorCode.EXTENDS_DEFERRED_CLASS);
  }

  /**
   * Verify that the given extends [clause] does not extend classes such as