pkg/analysis_server/lib/src/services/correction/fix_internal.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:async';
import 'dart:collection';
import 'dart:core';

import 'package:analysis_server/plugin/edit/fix/fix_core.dart';
import 'package:analysis_server/plugin/edit/fix/fix_dart.dart';
import 'package:analysis_server/src/services/completion/dart/utilities.dart';
import 'package:analysis_server/src/services/correction/fix.dart';
import 'package:analysis_server/src/services/correction/levenshtein.dart';
import 'package:analysis_server/src/services/correction/namespace.dart';
import 'package:analysis_server/src/services/correction/strings.dart';
import 'package:analysis_server/src/services/correction/util.dart';
import 'package:analysis_server/src/services/search/hierarchy.dart';
import 'package:analysis_server/src/utilities/flutter.dart' as flutter;
import 'package:analyzer/dart/analysis/session.dart';
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/element/element.dart';
import 'package:analyzer/dart/element/type.dart';
import 'package:analyzer/error/error.dart';
import 'package:analyzer/exception/exception.dart';
import 'package:analyzer/file_system/file_system.dart';
import 'package:analyzer/src/context/context_root.dart';
import 'package:analyzer/src/dart/analysis/driver.dart';
import 'package:analyzer/src/dart/analysis/session_helper.dart';
import 'package:analyzer/src/dart/analysis/top_level_declaration.dart';
import 'package:analyzer/src/dart/ast/ast.dart';
import 'package:analyzer/src/dart/ast/token.dart';
import 'package:analyzer/src/dart/ast/utilities.dart';
import 'package:analyzer/src/dart/element/ast_provider.dart';
import 'package:analyzer/src/dart/element/element.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/inheritance_override.dart';
import 'package:analyzer/src/generated/engine.dart';
import 'package:analyzer/src/generated/error_verifier.dart';
import 'package:analyzer/src/generated/java_core.dart';
import 'package:analyzer/src/generated/parser.dart';
import 'package:analyzer/src/generated/resolver.dart';
import 'package:analyzer/src/generated/source.dart';
import 'package:analyzer_plugin/protocol/protocol_common.dart'
    hide AnalysisError, Element, ElementKind;
import 'package:analyzer_plugin/src/utilities/string_utilities.dart';
import 'package:analyzer_plugin/utilities/change_builder/change_builder_dart.dart';
import 'package:analyzer_plugin/utilities/fixes/fixes.dart' hide FixContributor;
import 'package:analyzer_plugin/utilities/range_factory.dart';
import 'package:path/path.dart';

/**
 * A predicate is a one-argument function that returns a boolean value.
 */
typedef bool ElementPredicate(Element argument);

/**
 * The implementation of [DartFixContext].
 *
 * Clients may not extend, implement or mix-in this class.
 */
class DartFixContextImpl extends FixContextImpl implements DartFixContext {
  @override
  final AstProvider astProvider;

  @override
  final CompilationUnit unit;

  DartFixContextImpl(FixContext fixContext, this.astProvider, this.unit)
      : super.from(fixContext);

  GetTopLevelDeclarations get getTopLevelDeclarations =>
      analysisDriver.getTopLevelNameDeclarations;
}

/**
 * A [FixContributor] that provides the default set of fixes.
 */
class DefaultFixContributor extends DartFixContributor {
  @override
  Future<List<Fix>> internalComputeFixes(DartFixContext context) async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    try {
      FixProcessor processor = new FixProcessor(context);
      List<Fix> fixes = await processor.compute();
      List<Fix> fixAllFixes = await _computeFixAllFixes(context, fixes);
      return new List.from(fixes)..addAll(fixAllFixes);
    } on CancelCorrectionException {
      return const <Fix>[];
    }
  }

  Future<List<Fix>> _computeFixAllFixes(
      DartFixContext context, List<Fix> fixes) async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    final AnalysisError analysisError = context.error;
    final List<AnalysisError> allAnalysisErrors = context.errors;

    // Validate inputs:
    // - return if no fixes
    // - return if no other analysis errors
    if (fixes.isEmpty || allAnalysisErrors.length < 2) {
      return const <Fix>[];
    }

    // Remove any analysis errors that don't have the expected error code name
    allAnalysisErrors
        .removeWhere((e) => analysisError.errorCode.name != e.errorCode.name);
    if (allAnalysisErrors.length < 2) {
      return const <Fix>[];
    }

    // A map between each FixKind and the List of associated fixes
    final HashMap<FixKind, List<Fix>> map = new HashMap();

    // Populate the HashMap by looping through all AnalysisErrors, creating a
    // new FixProcessor to compute the other fixes that can be applied with this
    // one.
    // For each fix, put the fix into the HashMap.
    for (int i = 0; i < allAnalysisErrors.length; i++) {
      final FixContext fixContextI = new FixContextImpl(
          context.resourceProvider,
          context.analysisDriver,
          allAnalysisErrors[i],
          allAnalysisErrors);
      final DartFixContextImpl dartFixContextI = new DartFixContextImpl(
          fixContextI, context.astProvider, context.unit);
      final FixProcessor processorI = new FixProcessor(dartFixContextI);
      final List<Fix> fixesListI = await processorI.compute();
      for (Fix f in fixesListI) {
        if (!map.containsKey(f.kind)) {
          map[f.kind] = new List<Fix>()..add(f);
        } else {
          map[f.kind].add(f);
        }
      }
    }

    // For each FixKind in the HashMap, union each list together, then return
    // the set of unioned Fixes.
    final List<Fix> result = new List<Fix>();
    map.forEach((FixKind kind, List<Fix> fixesListJ) {
      if (fixesListJ.first.kind.canBeAppliedTogether()) {
        Fix unionFix = _unionFixList(fixesListJ);
        if (unionFix != null) {
          result.add(unionFix);
        }
      }
    });
    return result;
  }

  Fix _unionFixList(List<Fix> fixList) {
    if (fixList == null || fixList.isEmpty) {
      return null;
    } else if (fixList.length == 1) {
      return fixList[0];
    }
    final SourceChange sourceChange =
        new SourceChange(fixList[0].kind.appliedTogetherMessage);
    sourceChange.edits = new List.from(fixList[0].change.edits);
    final List<SourceEdit> edits = new List<SourceEdit>();
    edits.addAll(fixList[0].change.edits[0].edits);
    sourceChange.linkedEditGroups =
        new List.from(fixList[0].change.linkedEditGroups);
    for (int i = 1; i < fixList.length; i++) {
      edits.addAll(fixList[i].change.edits[0].edits);
      sourceChange.linkedEditGroups..addAll(fixList[i].change.linkedEditGroups);
    }
    // Sort the list of SourceEdits so that when the edits are applied, they
    // are applied from the end of the file to the top of the file.
    edits.sort((s1, s2) => s2.offset - s1.offset);

    sourceChange.edits[0].edits = edits;

    return new Fix(fixList[0].kind, sourceChange);
  }
}

/**
 * The computer for Dart fixes.
 */
class FixProcessor {
  static const int MAX_LEVENSHTEIN_DISTANCE = 3;

  ResourceProvider resourceProvider;
  AstProvider astProvider;
  GetTopLevelDeclarations getTopLevelDeclarations;
  CompilationUnit unit;
  AnalysisError error;

  /**
   * The analysis driver being used to perform analysis.
   */
  AnalysisDriver driver;

  /**
   * The analysis session to be used to create the change builder.
   */
  AnalysisSession session;

  /**
   * The helper wrapper around the [session].
   */
  AnalysisSessionHelper sessionHelper;

  String file;
  CompilationUnitElement unitElement;
  Source unitSource;
  LibraryElement unitLibraryElement;
  File unitLibraryFile;
  Folder unitLibraryFolder;

  final List<Fix> fixes = <Fix>[];

  CorrectionUtils utils;
  int errorOffset;
  int errorLength;
  int errorEnd;
  SourceRange errorRange;
  AstNode node;
  AstNode coveredNode;

  TypeProvider _typeProvider;
  TypeSystem _typeSystem;

  FixProcessor(DartFixContext dartContext) {
    resourceProvider = dartContext.resourceProvider;
    astProvider = dartContext.astProvider;
    getTopLevelDeclarations = dartContext.getTopLevelDeclarations;

    driver = dartContext.analysisDriver;
    session = driver.currentSession;
    sessionHelper = new AnalysisSessionHelper(session);

    // unit
    unit = dartContext.unit;
    unitElement = unit.declaredElement;
    unitSource = unitElement.source;
    // file
    file = unitSource.fullName;
    // library
    unitLibraryElement = unitElement.library;
    String unitLibraryPath = unitLibraryElement.source.fullName;
    unitLibraryFile = resourceProvider.getFile(unitLibraryPath);
    unitLibraryFolder = unitLibraryFile.parent;
    // error
    error = dartContext.error;
  }

  DartType get coreTypeBool => _getCoreType('bool');

  /**
   * Returns the EOL to use for this [CompilationUnit].
   */
  String get eol => utils.endOfLine;

  TypeProvider get typeProvider {
    if (_typeProvider == null) {
      _typeProvider = unitElement.context.typeProvider;
    }
    return _typeProvider;
  }

  TypeSystem get typeSystem {
    if (_typeSystem == null) {
      _typeSystem = new StrongTypeSystemImpl(typeProvider);
    }
    return _typeSystem;
  }

  Future<List<Fix>> compute() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    try {
      utils = new CorrectionUtils(unit);
    } catch (e) {
      throw new CancelCorrectionException(exception: e);
    }

    errorOffset = error.offset;
    errorLength = error.length;
    errorEnd = errorOffset + errorLength;
    errorRange = new SourceRange(errorOffset, errorLength);
    node = new NodeLocator2(errorOffset).searchWithin(unit);
    coveredNode =
        new NodeLocator2(errorOffset, errorEnd - 1).searchWithin(unit);
    if (coveredNode == null) {
      // TODO(brianwilkerson) Figure out why the coveredNode is sometimes null.
      return fixes;
    }

    // analyze ErrorCode
    ErrorCode errorCode = error.errorCode;
    if (errorCode == StaticWarningCode.UNDEFINED_CLASS_BOOLEAN) {
      await _addFix_boolInsteadOfBoolean();
    }
    if (errorCode ==
        CompileTimeErrorCode.CONST_INITIALIZED_WITH_NON_CONSTANT_VALUE) {
      await _addFix_replaceWithConstInstanceCreation();
    }
    if (errorCode == CompileTimeErrorCode.ASYNC_FOR_IN_WRONG_CONTEXT ||
        errorCode == StaticWarningCode.UNDEFINED_IDENTIFIER_AWAIT) {
      await _addFix_addAsync();
    }
    if ((errorCode == CompileTimeErrorCode.BUILT_IN_IDENTIFIER_AS_TYPE ||
            errorCode == ParserErrorCode.UNEXPECTED_TOKEN) &&
        error.message.indexOf("'await'") >= 0) {
      await _addFix_addAsync();
    }
    if (errorCode == CompileTimeErrorCode.INTEGER_LITERAL_IMPRECISE_AS_DOUBLE) {
      await _addFix_changeToNearestPreciseValue();
    }

    if (errorCode == CompileTimeErrorCode.INVALID_ANNOTATION ||
        errorCode == CompileTimeErrorCode.UNDEFINED_ANNOTATION) {
      if (node is Annotation) {
        Annotation annotation = node;
        Identifier name = annotation.name;
        if (name != null && name.staticElement == null) {
          node = name;
          if (annotation.arguments == null) {
            await _addFix_importLibrary_withTopLevelVariable();
          } else {
            await _addFix_importLibrary_withType();
            await _addFix_createClass();
            await _addFix_undefinedClass_useSimilar();
          }
        }
      }
    }
    if (errorCode ==
        CompileTimeErrorCode.NO_DEFAULT_SUPER_CONSTRUCTOR_EXPLICIT) {
      await _addFix_createConstructorSuperExplicit();
    }
    if (errorCode ==
        CompileTimeErrorCode.NO_DEFAULT_SUPER_CONSTRUCTOR_IMPLICIT) {
      await _addFix_createConstructorSuperImplicit();
      // TODO(brianwilkerson) The following was added because fasta produces
      // NO_DEFAULT_SUPER_CONSTRUCTOR_IMPLICIT in places where analyzer produced
      // NO_DEFAULT_SUPER_CONSTRUCTOR_EXPLICIT
      await _addFix_createConstructorSuperExplicit();
    }
    if (errorCode ==
        CompileTimeErrorCode.UNDEFINED_CONSTRUCTOR_IN_INITIALIZER_DEFAULT) {
      await _addFix_createConstructorSuperExplicit();
    }
    if (errorCode == CompileTimeErrorCode.URI_DOES_NOT_EXIST) {
      await _addFix_createImportUri();
      await _addFix_createPartUri();
    }
    if (errorCode == HintCode.CAN_BE_NULL_AFTER_NULL_AWARE) {
      await _addFix_canBeNullAfterNullAware();
    }
    if (errorCode == HintCode.DEAD_CODE) {
      await _addFix_removeDeadCode();
    }
    if (errorCode == HintCode.DIVISION_OPTIMIZATION) {
      await _addFix_useEffectiveIntegerDivision();
    }
    if (errorCode == HintCode.TYPE_CHECK_IS_NOT_NULL) {
      await _addFix_isNotNull();
    }
    if (errorCode == HintCode.TYPE_CHECK_IS_NULL) {
      await _addFix_isNull();
    }
    if (errorCode == HintCode.UNDEFINED_GETTER) {
      await _addFix_undefinedClassAccessor_useSimilar();
      await _addFix_createField();
      await _addFix_createGetter();
    }
    if (errorCode == HintCode.UNDEFINED_SETTER) {
      await _addFix_undefinedClassAccessor_useSimilar();
      await _addFix_createField();
    }
    if (errorCode == HintCode.UNNECESSARY_CAST) {
      await _addFix_removeUnnecessaryCast();
    }
    if (errorCode == HintCode.UNUSED_CATCH_CLAUSE) {
      await _addFix_removeUnusedCatchClause();
    }
    if (errorCode == HintCode.UNUSED_CATCH_STACK) {
      await _addFix_removeUnusedCatchStack();
    }
    if (errorCode == HintCode.UNUSED_IMPORT) {
      await _addFix_removeUnusedImport();
    }
    if (errorCode == ParserErrorCode.EXPECTED_TOKEN) {
      await _addFix_insertSemicolon();
    }
    if (errorCode == ParserErrorCode.GETTER_WITH_PARAMETERS) {
      await _addFix_removeParameters_inGetterDeclaration();
    }
    if (errorCode == ParserErrorCode.VAR_AS_TYPE_NAME) {
      await _addFix_replaceVarWithDynamic();
    }
    if (errorCode == StaticWarningCode.ASSIGNMENT_TO_FINAL) {
      await _addFix_makeFieldNotFinal();
    }
    if (errorCode == StaticWarningCode.CONCRETE_CLASS_WITH_ABSTRACT_MEMBER) {
      await _addFix_makeEnclosingClassAbstract();
    }
    if (errorCode == CompileTimeErrorCode.EXTRA_POSITIONAL_ARGUMENTS ||
        errorCode == StaticWarningCode.EXTRA_POSITIONAL_ARGUMENTS ||
        errorCode ==
            CompileTimeErrorCode.EXTRA_POSITIONAL_ARGUMENTS_COULD_BE_NAMED ||
        errorCode ==
            StaticWarningCode.EXTRA_POSITIONAL_ARGUMENTS_COULD_BE_NAMED) {
      await _addFix_createConstructor_insteadOfSyntheticDefault();
      await _addFix_addMissingParameter();
    }
    if (errorCode == HintCode.MISSING_REQUIRED_PARAM ||
        errorCode == HintCode.MISSING_REQUIRED_PARAM_WITH_DETAILS) {
      await _addFix_addMissingRequiredArgument();
    }
    if (errorCode == StaticWarningCode.NEW_WITH_UNDEFINED_CONSTRUCTOR) {
      await _addFix_createConstructor_named();
    }
    if (errorCode == StaticWarningCode.CONCRETE_CLASS_WITH_ABSTRACT_MEMBER ||
        errorCode ==
            StaticWarningCode.NON_ABSTRACT_CLASS_INHERITS_ABSTRACT_MEMBER_ONE ||
        errorCode ==
            StaticWarningCode.NON_ABSTRACT_CLASS_INHERITS_ABSTRACT_MEMBER_TWO ||
        errorCode ==
            StaticWarningCode
                .NON_ABSTRACT_CLASS_INHERITS_ABSTRACT_MEMBER_THREE ||
        errorCode ==
            StaticWarningCode
                .NON_ABSTRACT_CLASS_INHERITS_ABSTRACT_MEMBER_FOUR ||
        errorCode ==
            StaticWarningCode
                .NON_ABSTRACT_CLASS_INHERITS_ABSTRACT_MEMBER_FIVE_PLUS) {
      // make class abstract
      await _addFix_makeEnclosingClassAbstract();
      await _addFix_createNoSuchMethod();
      // implement methods
      await _addFix_createMissingOverrides();
    }
    if (errorCode == CompileTimeErrorCode.UNDEFINED_CLASS ||
        errorCode == StaticWarningCode.CAST_TO_NON_TYPE ||
        errorCode == StaticWarningCode.NOT_A_TYPE ||
        errorCode == StaticWarningCode.TYPE_TEST_WITH_UNDEFINED_NAME ||
        errorCode == StaticWarningCode.UNDEFINED_CLASS) {
      await _addFix_importLibrary_withType();
      await _addFix_createClass();
      await _addFix_createMixin();
      await _addFix_undefinedClass_useSimilar();
    }
    if (errorCode ==
            CompileTimeErrorCode.EXTRA_POSITIONAL_ARGUMENTS_COULD_BE_NAMED ||
        errorCode ==
            StaticWarningCode.EXTRA_POSITIONAL_ARGUMENTS_COULD_BE_NAMED) {
      await _addFix_convertToNamedArgument();
    }
    if (errorCode == StaticWarningCode.FINAL_NOT_INITIALIZED) {
      await _addFix_createConstructor_forUninitializedFinalFields();
    }
    if (errorCode == StaticWarningCode.FINAL_NOT_INITIALIZED_CONSTRUCTOR_1 ||
        errorCode == StaticWarningCode.FINAL_NOT_INITIALIZED_CONSTRUCTOR_2 ||
        errorCode ==
            StaticWarningCode.FINAL_NOT_INITIALIZED_CONSTRUCTOR_3_PLUS) {
      await _addFix_updateConstructor_forUninitializedFinalFields();
    }
    if (errorCode == StaticWarningCode.UNDEFINED_IDENTIFIER) {
      await _addFix_undefinedClassAccessor_useSimilar();
      await _addFix_createClass();
      await _addFix_createField();
      await _addFix_createGetter();
      await _addFix_createFunction_forFunctionType();
      await _addFix_createMixin();
      await _addFix_importLibrary_withType();
      await _addFix_importLibrary_withTopLevelVariable();
      await _addFix_createLocalVariable();
    }
    if (errorCode == CompileTimeErrorCode.UNDEFINED_NAMED_PARAMETER ||
        errorCode == StaticWarningCode.UNDEFINED_NAMED_PARAMETER) {
      await _addFix_addMissingNamedArgument();
    }
    if (errorCode == StaticTypeWarningCode.UNDEFINED_METHOD_WITH_CONSTRUCTOR) {
      await _addFix_undefinedMethodWithContructor();
    }
    if (errorCode == StaticTypeWarningCode.ILLEGAL_ASYNC_RETURN_TYPE) {
      await _addFix_illegalAsyncReturnType();
    }
    if (errorCode == StaticTypeWarningCode.INSTANCE_ACCESS_TO_STATIC_MEMBER) {
      await _addFix_useStaticAccess_method();
      await _addFix_useStaticAccess_property();
    }
    if (errorCode == StaticTypeWarningCode.INVALID_ASSIGNMENT) {
      await _addFix_addExplicitCast();
      await _addFix_changeTypeAnnotation();
    }
    if (errorCode == StaticTypeWarningCode.INVOCATION_OF_NON_FUNCTION) {
      await _addFix_removeParentheses_inGetterInvocation();
    }
    if (errorCode == StaticTypeWarningCode.NON_BOOL_CONDITION) {
      await _addFix_nonBoolCondition_addNotNull();
    }
    if (errorCode == StaticTypeWarningCode.NON_TYPE_AS_TYPE_ARGUMENT) {
      await _addFix_importLibrary_withType();
      await _addFix_createClass();
      await _addFix_createMixin();
    }
    if (errorCode == StaticTypeWarningCode.UNDEFINED_FUNCTION) {
      await _addFix_createClass();
      await _addFix_importLibrary_withFunction();
      await _addFix_importLibrary_withType();
      await _addFix_undefinedFunction_useSimilar();
      await _addFix_undefinedFunction_create();
    }
    if (errorCode == StaticTypeWarningCode.UNDEFINED_GETTER) {
      await _addFix_undefinedClassAccessor_useSimilar();
      await _addFix_createField();
      await _addFix_createGetter();
      await _addFix_createFunction_forFunctionType();
      // TODO(brianwilkerson) The following were added because fasta produces
      // UNDEFINED_GETTER in places where analyzer produced UNDEFINED_IDENTIFIER
      await _addFix_createClass();
      await _addFix_createMixin();
      await _addFix_createLocalVariable();
      await _addFix_importLibrary_withTopLevelVariable();
      await _addFix_importLibrary_withType();
    }
    if (errorCode == HintCode.UNDEFINED_METHOD ||
        errorCode == StaticTypeWarningCode.UNDEFINED_METHOD) {
      await _addFix_createClass();
      await _addFix_importLibrary_withFunction();
      await _addFix_importLibrary_withType();
      await _addFix_undefinedMethod_useSimilar();
      await _addFix_undefinedMethod_create();
      await _addFix_undefinedFunction_create();
    }
    if (errorCode == StaticTypeWarningCode.UNDEFINED_SETTER) {
      await _addFix_undefinedClassAccessor_useSimilar();
      await _addFix_createField();
    }
    if (errorCode == CompileTimeErrorCode.UNDEFINED_NAMED_PARAMETER ||
        errorCode == StaticWarningCode.UNDEFINED_NAMED_PARAMETER) {
      await _addFix_convertFlutterChild();
      await _addFix_convertFlutterChildren();
    }
    if (errorCode ==
        CompileTimeErrorCode.INITIALIZING_FORMAL_FOR_NON_EXISTENT_FIELD) {
      await _addFix_createField_initializingFormal();
    }
    if (errorCode == CompileTimeErrorCode.CONST_INSTANCE_FIELD) {
      await _addFix_addStatic();
    }
    // lints
    if (errorCode is LintCode) {
      String name = errorCode.name;
      if (name == LintNames.always_require_non_null_named_parameters) {
        await _addFix_addRequiredAnnotation();
      }
      if (name == LintNames.annotate_overrides) {
        await _addFix_addOverrideAnnotation();
      }
      if (name == LintNames.avoid_annotating_with_dynamic) {
        await _addFix_removeTypeAnnotation();
      }
      if (name == LintNames.avoid_empty_else) {
        await _addFix_removeEmptyElse();
      }
      if (name == LintNames.avoid_init_to_null) {
        await _addFix_removeInitializer();
      }
      if (name == LintNames.avoid_return_types_on_setters) {
        await _addFix_removeTypeAnnotation();
      }
      if (name == LintNames.avoid_types_on_closure_parameters) {
        await _addFix_replaceWithIdentifier();
      }
      if (name == LintNames.await_only_futures) {
        await _addFix_removeAwait();
      }
      if (name == LintNames.empty_catches) {
        await _addFix_removeEmptyCatch();
      }
      if (name == LintNames.empty_constructor_bodies) {
        await _addFix_removeEmptyConstructorBody();
      }
      if (name == LintNames.empty_statements) {
        await _addFix_removeEmptyStatement();
      }
      if (name == LintNames.non_constant_identifier_names) {
        await _addFix_renameToCamelCase();
      }
      if (name == LintNames.prefer_collection_literals) {
        await _addFix_replaceWithLiteral();
      }
      if (name == LintNames.prefer_conditional_assignment) {
        await _addFix_replaceWithConditionalAssignment();
      }
      if (errorCode.name == LintNames.prefer_const_declarations) {
        await _addFix_replaceFinalWithConst();
      }
      if (name == LintNames.prefer_final_fields) {
        await _addFix_makeVariableFinal();
      }
      if (name == LintNames.prefer_final_locals) {
        await _addFix_makeVariableFinal();
      }
      if (name == LintNames.prefer_is_not_empty) {
        await _addFix_isNotEmpty();
      }
      if (name == LintNames.type_init_formals) {
        await _addFix_removeTypeAnnotation();
      }
      if (name == LintNames.unnecessary_brace_in_string_interp) {
        await _addFix_removeInterpolationBraces();
      }
      if (name == LintNames.unnecessary_lambdas) {
        await _addFix_replaceWithTearOff();
      }
      if (name == LintNames.unnecessary_override) {
        await _addFix_removeMethodDeclaration();
      }
      if (name == LintNames.unnecessary_this) {
        await _addFix_removeThisExpression();
      }
    }
    // done
    return fixes;
  }

  Future<void> _addFix_addAsync() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    FunctionBody body = node.getAncestor((n) => n is FunctionBody);
    if (body != null && body.keyword == null) {
      TypeProvider typeProvider = await this.typeProvider;
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.convertFunctionFromSyncToAsync(body, typeProvider);
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.ADD_ASYNC);
    }
  }

  Future<void> _addFix_addExplicitCast() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (coveredNode is! Expression) {
      return;
    }
    Expression target = coveredNode;
    DartType fromType = target.staticType;
    DartType toType;
    AstNode parent = target.parent;
    if (parent is AssignmentExpression && target == parent.rightHandSide) {
      toType = parent.leftHandSide.staticType;
    } else if (parent is VariableDeclaration && target == parent.initializer) {
      toType = parent.name.staticType;
    } else {
      // TODO(brianwilkerson) Handle function arguments.
      return;
    }
    // TODO(brianwilkerson) Handle `toSet` in a manner similar to the below.
    if (_isToListMethodInvocation(target)) {
      Expression targetTarget = (target as MethodInvocation).target;
      if (targetTarget != null) {
        DartType targetTargetType = targetTarget.staticType;
        if (_isDartCoreIterable(targetTargetType) ||
            _isDartCoreList(targetTargetType) ||
            _isDartCoreMap(targetTargetType) ||
            _isDartCoreSet(targetTargetType)) {
          target = targetTarget;
          fromType = targetTargetType;
        }
      }
    }
    if (target is AsExpression) {
      // TODO(brianwilkerson) Consider updating the right operand.
      return;
    }
    bool needsParentheses = target.precedence < 15;
    if (((_isDartCoreIterable(fromType) || _isDartCoreList(fromType)) &&
            _isDartCoreList(toType)) ||
        (_isDartCoreSet(fromType) && _isDartCoreSet(toType))) {
      if (_isCastMethodInvocation(target)) {
        // TODO(brianwilkerson) Consider updating the type arguments to the
        // `cast` invocation.
        return;
      }
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        if (needsParentheses) {
          builder.addSimpleInsertion(target.offset, '(');
        }
        builder.addInsertion(target.end, (DartEditBuilder builder) {
          if (needsParentheses) {
            builder.write(')');
          }
          builder.write('.cast<');
          builder.writeType((toType as InterfaceType).typeArguments[0]);
          builder.write('>()');
        });
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.ADD_EXPLICIT_CAST);
    } else if (_isDartCoreMap(fromType) && _isDartCoreMap(toType)) {
      if (_isCastMethodInvocation(target)) {
        // TODO(brianwilkerson) Consider updating the type arguments to the
        // `cast` invocation.
        return;
      }
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        if (needsParentheses) {
          builder.addSimpleInsertion(target.offset, '(');
        }
        builder.addInsertion(target.end, (DartEditBuilder builder) {
          if (needsParentheses) {
            builder.write(')');
          }
          builder.write('.cast<');
          builder.writeType((toType as InterfaceType).typeArguments[0]);
          builder.write(', ');
          builder.writeType((toType as InterfaceType).typeArguments[1]);
          builder.write('>()');
        });
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.ADD_EXPLICIT_CAST);
    } else {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        if (needsParentheses) {
          builder.addSimpleInsertion(target.offset, '(');
        }
        builder.addInsertion(target.end, (DartEditBuilder builder) {
          if (needsParentheses) {
            builder.write(')');
          }
          builder.write(' as ');
          builder.writeType(toType);
        });
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.ADD_EXPLICIT_CAST);
    }
  }

  Future<void> _addFix_addMissingNamedArgument() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // Prepare the name of the missing parameter.
    if (this.node is! SimpleIdentifier) {
      return;
    }
    SimpleIdentifier node = this.node;
    String name = node.name;

    // We expect that the node is part of a NamedExpression.
    if (node.parent?.parent is! NamedExpression) {
      return;
    }
    NamedExpression namedExpression = node.parent.parent;

    // We should be in an ArgumentList.
    if (namedExpression.parent is! ArgumentList) {
      return;
    }
    AstNode argumentList = namedExpression.parent;

    // Prepare the invoked element.
    var context = new _ExecutableParameters(astProvider, argumentList.parent);
    if (context == null) {
      return;
    }

    // We cannot add named parameters when there are positional positional.
    if (context.optionalPositional.isNotEmpty) {
      return;
    }

    Future<void> addParameter(int offset, String prefix, String suffix) async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
      await null;
      if (offset != null) {
        var changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(context.file, (builder) {
          builder.addInsertion(offset, (builder) {
            builder.write(prefix);
            builder.writeParameterMatchingArgument(
                namedExpression, 0, new Set<String>());
            builder.write(suffix);
          });
        });
        _addFixFromBuilder(
            changeBuilder, DartFixKind.ADD_MISSING_PARAMETER_NAMED,
            args: [name]);
      }
    }

    if (context.named.isNotEmpty) {
      var prevNode = await context.getParameterNode(context.named.last);
      await addParameter(prevNode?.end, ', ', '');
    } else if (context.required.isNotEmpty) {
      var prevNode = await context.getParameterNode(context.required.last);
      await addParameter(prevNode?.end, ', {', '}');
    } else {
      var parameterList = await context.getParameterList();
      await addParameter(parameterList?.leftParenthesis?.end, '{', '}');
    }
  }

  Future<void> _addFix_addMissingParameter() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // The error is reported on ArgumentList.
    if (node is! ArgumentList) {
      return;
    }
    ArgumentList argumentList = node;
    List<Expression> arguments = argumentList.arguments;

    // Prepare the invoked element.
    var context = new _ExecutableParameters(astProvider, node.parent);
    if (context == null) {
      return;
    }

    // prepare the argument to add a new parameter for
    int numRequired = context.required.length;
    if (numRequired >= arguments.length) {
      return;
    }
    Expression argument = arguments[numRequired];

    Future<void> addParameter(
        FixKind kind, int offset, String prefix, String suffix) async {
      // TODO(brianwilkerson) Determine whether this await is necessary.
      await null;
      if (offset != null) {
        var changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(context.file, (builder) {
          builder.addInsertion(offset, (builder) {
            builder.write(prefix);
            builder.writeParameterMatchingArgument(
                argument, numRequired, new Set<String>());
            builder.write(suffix);
          });
        });
        _addFixFromBuilder(changeBuilder, kind);
      }
    }

    // Suggest adding a required parameter.
    {
      var kind = DartFixKind.ADD_MISSING_PARAMETER_REQUIRED;
      if (context.required.isNotEmpty) {
        var prevNode = await context.getParameterNode(context.required.last);
        await addParameter(kind, prevNode?.end, ', ', '');
      } else {
        var parameterList = await context.getParameterList();
        var offset = parameterList?.leftParenthesis?.end;
        var suffix = context.executable.parameters.isNotEmpty ? ', ' : '';
        await addParameter(kind, offset, '', suffix);
      }
    }

    // Suggest adding the first optional positional parameter.
    if (context.optionalPositional.isEmpty && context.named.isEmpty) {
      var kind = DartFixKind.ADD_MISSING_PARAMETER_POSITIONAL;
      var prefix = context.required.isNotEmpty ? ', [' : '[';
      if (context.required.isNotEmpty) {
        var prevNode = await context.getParameterNode(context.required.last);
        await addParameter(kind, prevNode?.end, prefix, ']');
      } else {
        var parameterList = await context.getParameterList();
        var offset = parameterList?.leftParenthesis?.end;
        await addParameter(kind, offset, prefix, ']');
      }
    }
  }

  Future<void> _addFix_addMissingRequiredArgument() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    InstanceCreationExpression creation;
    Element targetElement;
    ArgumentList argumentList;

    if (node is SimpleIdentifier) {
      AstNode invocation = node.parent;
      if (invocation is MethodInvocation) {
        targetElement = invocation.methodName.staticElement;
        argumentList = invocation.argumentList;
      } else {
        creation =
            invocation.getAncestor((p) => p is InstanceCreationExpression);
        if (creation != null) {
          targetElement = creation.staticElement;
          argumentList = creation.argumentList;
        }
      }
    }

    if (targetElement is ExecutableElement) {
      // Format: "Missing required argument 'foo"
      List<String> messageParts = error.message.split("'");
      if (messageParts.length < 2) {
        return;
      }
      String missingParameterName = messageParts[1];

      ParameterElement missingParameter = targetElement.parameters.firstWhere(
          (p) => p.name == missingParameterName,
          orElse: () => null);
      if (missingParameter == null) {
        return;
      }

      int offset;
      bool hasTrailingComma = false;
      List<Expression> arguments = argumentList.arguments;
      if (arguments.isEmpty) {
        offset = argumentList.leftParenthesis.end;
      } else {
        Expression lastArgument = arguments.last;
        offset = lastArgument.end;
        hasTrailingComma = lastArgument.endToken.next.type == TokenType.COMMA;
      }

      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addInsertion(offset, (DartEditBuilder builder) {
          if (arguments.isNotEmpty) {
            builder.write(', ');
          }
          String defaultValue =
              getDefaultStringParameterValue(missingParameter);
          builder.write('$missingParameterName: $defaultValue');
          // Insert a trailing comma after Flutter instance creation params.
          if (!hasTrailingComma && flutter.isWidgetExpression(creation)) {
            builder.write(',');
          }
        });
      });
      _addFixFromBuilder(
          changeBuilder, DartFixKind.ADD_MISSING_REQUIRED_ARGUMENT,
          args: [missingParameterName]);
    }
  }

  Future<void> _addFix_addOverrideAnnotation() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    ClassMember member = node.getAncestor((n) => n is ClassMember);
    if (member == null) {
      return;
    }

    //TODO(pq): migrate annotation edit building to change_builder

    // Handle doc comments.
    Token token = member.beginToken;
    if (token is CommentToken) {
      token = (token as CommentToken).parent;
    }

    Position exitPosition = new Position(file, token.offset - 1);
    String indent = utils.getIndent(1);
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleReplacement(
          range.startLength(token, 0), '@override$eol$indent');
    });
    changeBuilder.setSelection(exitPosition);
    _addFixFromBuilder(changeBuilder, DartFixKind.LINT_ADD_OVERRIDE);
  }

  Future<void> _addFix_addRequiredAnnotation() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleInsertion(node.parent.offset, '@required ');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.LINT_ADD_REQUIRED);
  }

  Future<void> _addFix_addStatic() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    FieldDeclaration declaration =
        node.getAncestor((n) => n is FieldDeclaration);
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleInsertion(declaration.offset, 'static ');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.ADD_STATIC);
  }

  Future<void> _addFix_boolInsteadOfBoolean() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleReplacement(range.error(error), 'bool');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.REPLACE_BOOLEAN_WITH_BOOL);
  }

  Future<void> _addFix_canBeNullAfterNullAware() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode node = coveredNode;
    if (node is Expression) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        AstNode parent = node.parent;
        while (parent != null) {
          if (parent is MethodInvocation && parent.target == node) {
            builder.addSimpleReplacement(range.token(parent.operator), '?.');
          } else if (parent is PropertyAccess && parent.target == node) {
            builder.addSimpleReplacement(range.token(parent.operator), '?.');
          } else {
            break;
          }
          node = parent;
          parent = node.parent;
        }
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REPLACE_WITH_NULL_AWARE);
    }
  }

  Future<void> _addFix_changeToNearestPreciseValue() async {
    IntegerLiteral integer = node;
    String lexeme = integer.literal.lexeme;
    BigInt precise = BigInt.from(IntegerLiteralImpl.nearestValidDouble(lexeme));
    String correction = lexeme.toLowerCase().contains('x')
        ? '0x${precise.toRadixString(16).toUpperCase()}'
        : precise.toString();
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleReplacement(range.node(integer), correction);
    });
    _addFixFromBuilder(
        changeBuilder, DartFixKind.CHANGE_TO_NEAREST_PRECISE_VALUE,
        args: [correction]);
  }

  Future<void> _addFix_changeTypeAnnotation() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode declaration = coveredNode.parent;
    if (declaration is VariableDeclaration &&
        declaration.initializer == coveredNode) {
      AstNode variableList = declaration.parent;
      if (variableList is VariableDeclarationList &&
          variableList.variables.length == 1) {
        TypeAnnotation typeNode = variableList.type;
        if (typeNode != null) {
          Expression initializer = coveredNode;
          DartType newType = initializer.staticType;
          if (newType is InterfaceType || newType is FunctionType) {
            DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
            await changeBuilder.addFileEdit(file,
                (DartFileEditBuilder builder) {
              builder.addReplacement(range.node(typeNode),
                  (DartEditBuilder builder) {
                builder.writeType(newType);
              });
            });
            _addFixFromBuilder(
                changeBuilder, DartFixKind.CHANGE_TYPE_ANNOTATION, args: [
              resolutionMap.typeForTypeName(typeNode),
              newType.displayName
            ]);
          }
        }
      }
    }
  }

  Future<void> _addFix_convertFlutterChild() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    NamedExpression named = flutter.findNamedExpression(node, 'child');
    if (named == null) {
      return;
    }

    // child: widget
    Expression expression = named.expression;
    if (flutter.isWidgetExpression(expression)) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        flutter.convertChildToChildren2(
            builder,
            expression,
            named,
            eol,
            utils.getNodeText,
            utils.getLinePrefix,
            utils.getIndent,
            utils.getText,
            range.node);
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.CONVERT_FLUTTER_CHILD);
      return;
    }

    // child: [widget1, widget2]
    if (expression is ListLiteral &&
        expression.elements.every(flutter.isWidgetExpression)) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addSimpleReplacement(range.node(named.name), 'children:');
        if (expression.typeArguments == null) {
          builder.addSimpleInsertion(expression.offset, '<Widget>');
        }
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.CONVERT_FLUTTER_CHILD);
    }
  }

  Future<void> _addFix_convertFlutterChildren() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode node = this.node;
    if (node is SimpleIdentifier &&
        node.name == 'children' &&
        node.parent?.parent is NamedExpression) {
      NamedExpression named = node.parent?.parent;
      Expression expression = named.expression;
      if (expression is ListLiteral && expression.elements.length == 1) {
        Expression widget = expression.elements[0];
        if (flutter.isWidgetExpression(widget)) {
          String widgetText = utils.getNodeText(widget);
          String indentOld = utils.getLinePrefix(widget.offset);
          String indentNew = utils.getLinePrefix(named.offset);
          widgetText = _replaceSourceIndent(widgetText, indentOld, indentNew);

          var builder = new DartChangeBuilder(session);
          await builder.addFileEdit(file, (builder) {
            builder.addReplacement(range.node(named), (builder) {
              builder.write('child: ');
              builder.write(widgetText);
            });
          });
          _addFixFromBuilder(builder, DartFixKind.CONVERT_FLUTTER_CHILDREN);
        }
      }
    }
  }

  Future<void> _addFix_convertToNamedArgument() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    var argumentList = this.node;
    if (argumentList is ArgumentList) {
      // Prepare ExecutableElement.
      ExecutableElement executable;
      var parent = argumentList.parent;
      if (parent is InstanceCreationExpression) {
        executable = parent.staticElement;
      } else if (parent is MethodInvocation) {
        executable = parent.methodName.staticElement;
      }
      if (executable == null) {
        return;
      }

      // Prepare named parameters.
      int numberOfPositionalParameters = 0;
      var namedParameters = <ParameterElement>[];
      for (var parameter in executable.parameters) {
        if (parameter.isNamed) {
          namedParameters.add(parameter);
        } else {
          numberOfPositionalParameters++;
        }
      }
      if (argumentList.arguments.length <= numberOfPositionalParameters) {
        return;
      }

      // Find named parameters for extra arguments.
      var argumentToParameter = <Expression, ParameterElement>{};
      Iterable<Expression> extraArguments =
          argumentList.arguments.skip(numberOfPositionalParameters);
      for (var argument in extraArguments) {
        if (argument is! NamedExpression) {
          ParameterElement uniqueNamedParameter = null;
          for (var namedParameter in namedParameters) {
            if (typeSystem.isSubtypeOf(
                argument.staticType, namedParameter.type)) {
              if (uniqueNamedParameter == null) {
                uniqueNamedParameter = namedParameter;
              } else {
                uniqueNamedParameter = null;
                break;
              }
            }
          }
          if (uniqueNamedParameter != null) {
            argumentToParameter[argument] = uniqueNamedParameter;
            namedParameters.remove(uniqueNamedParameter);
          }
        }
      }
      if (argumentToParameter.isEmpty) {
        return;
      }

      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        for (var argument in argumentToParameter.keys) {
          var parameter = argumentToParameter[argument];
          builder.addSimpleInsertion(argument.offset, '${parameter.name}: ');
        }
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.CONVERT_TO_NAMED_ARGUMENTS);
    }
  }

  Future<void> _addFix_createClass() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    Element prefixElement = null;
    String name = null;
    SimpleIdentifier nameNode;
    if (node is SimpleIdentifier) {
      AstNode parent = node.parent;
      if (parent is PrefixedIdentifier) {
        PrefixedIdentifier prefixedIdentifier = parent;
        prefixElement = prefixedIdentifier.prefix.staticElement;
        if (prefixElement == null) {
          return;
        }
        parent = prefixedIdentifier.parent;
        nameNode = prefixedIdentifier.identifier;
        name = prefixedIdentifier.identifier.name;
      } else {
        nameNode = node;
        name = nameNode.name;
      }
      if (!_mayBeTypeIdentifier(nameNode)) {
        return;
      }
    } else {
      return;
    }
    // prepare environment
    Element targetUnit;
    String prefix = '';
    String suffix = '';
    int offset = -1;
    String filePath;
    if (prefixElement == null) {
      targetUnit = unitElement;
      CompilationUnitMember enclosingMember = node.getAncestor((node) =>
          node is CompilationUnitMember && node.parent is CompilationUnit);
      if (enclosingMember == null) {
        return;
      }
      offset = enclosingMember.end;
      filePath = file;
      prefix = '$eol$eol';
    } else {
      for (ImportElement import in unitLibraryElement.imports) {
        if (prefixElement is PrefixElement && import.prefix == prefixElement) {
          LibraryElement library = import.importedLibrary;
          if (library != null) {
            targetUnit = library.definingCompilationUnit;
            Source targetSource = targetUnit.source;
            try {
              offset = targetSource.contents.data.length;
              filePath = targetSource.fullName;
              prefix = '$eol';
              suffix = '$eol';
            } on FileSystemException {
              // If we can't read the file to get the offset, then we can't
              // create a fix.
            }
            break;
          }
        }
      }
    }
    if (offset < 0) {
      return;
    }
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(filePath, (DartFileEditBuilder builder) {
      builder.addInsertion(offset, (DartEditBuilder builder) {
        builder.write(prefix);
        builder.writeClassDeclaration(name, nameGroupName: 'NAME');
        builder.write(suffix);
      });
      if (prefixElement == null) {
        builder.addLinkedPosition(range.node(node), 'NAME');
      }
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_CLASS, args: [name]);
  }

  /**
   * Here we handle cases when there are no constructors in a class, and the
   * class has uninitialized final fields.
   */
  Future<void> _addFix_createConstructor_forUninitializedFinalFields() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is! SimpleIdentifier || node.parent is! VariableDeclaration) {
      return;
    }

    ClassDeclaration classDeclaration =
        node.getAncestor((node) => node is ClassDeclaration);
    if (classDeclaration == null) {
      return;
    }
    String className = classDeclaration.name.name;
    InterfaceType superType = classDeclaration.declaredElement.supertype;

    // prepare names of uninitialized final fields
    List<String> fieldNames = <String>[];
    for (ClassMember member in classDeclaration.members) {
      if (member is FieldDeclaration) {
        VariableDeclarationList variableList = member.fields;
        if (variableList.isFinal) {
          fieldNames.addAll(variableList.variables
              .where((v) => v.initializer == null)
              .map((v) => v.name.name));
        }
      }
    }
    // prepare location for a new constructor
    ClassMemberLocation targetLocation =
        utils.prepareNewConstructorLocation(classDeclaration);

    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    if (flutter.isExactlyStatelessWidgetType(superType) ||
        flutter.isExactlyStatefulWidgetType(superType)) {
      // Specialize for Flutter widgets.
      ClassElement keyClass =
          await sessionHelper.getClass(flutter.WIDGETS_LIBRARY_URI, 'Key');
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
          builder.write(targetLocation.prefix);
          builder.write('const ');
          builder.write(className);
          builder.write('({');
          builder.writeType(keyClass.type);
          builder.write(' key');

          List<String> childrenFields = [];
          for (String fieldName in fieldNames) {
            if (fieldName == 'child' || fieldName == 'children') {
              childrenFields.add(fieldName);
              continue;
            }
            builder.write(', this.');
            builder.write(fieldName);
          }
          for (String fieldName in childrenFields) {
            builder.write(', this.');
            builder.write(fieldName);
          }

          builder.write('}) : super(key: key);');
          builder.write(targetLocation.suffix);
        });
      });
    } else {
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
          builder.write(targetLocation.prefix);
          builder.writeConstructorDeclaration(className,
              fieldNames: fieldNames);
          builder.write(targetLocation.suffix);
        });
      });
    }
    _addFixFromBuilder(
        changeBuilder, DartFixKind.CREATE_CONSTRUCTOR_FOR_FINAL_FIELDS);
  }

  Future<void> _addFix_createConstructor_insteadOfSyntheticDefault() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is! ArgumentList) {
      return;
    }
    if (node.parent is! InstanceCreationExpression) {
      return;
    }
    InstanceCreationExpression instanceCreation = node.parent;
    ConstructorName constructorName = instanceCreation.constructorName;
    // should be synthetic default constructor
    ConstructorElement constructorElement = constructorName.staticElement;
    if (constructorElement == null ||
        !constructorElement.isDefaultConstructor ||
        !constructorElement.isSynthetic) {
      return;
    }
    // prepare target
    if (constructorElement.enclosingElement is! ClassElement) {
      return;
    }
    ClassElement targetElement = constructorElement.enclosingElement;
    // prepare location for a new constructor
    AstNode targetTypeNode = getParsedClassElementNode(targetElement);
    if (targetTypeNode is! ClassDeclaration) {
      return;
    }
    ClassMemberLocation targetLocation =
        utils.prepareNewConstructorLocation(targetTypeNode);
    Source targetSource = targetElement.source;
    String targetFile = targetSource.fullName;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
      builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
        builder.write(targetLocation.prefix);
        builder.writeConstructorDeclaration(targetElement.name,
            argumentList: instanceCreation.argumentList);
        builder.write(targetLocation.suffix);
      });
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_CONSTRUCTOR,
        args: [constructorName]);
  }

  Future<void> _addFix_createConstructor_named() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    SimpleIdentifier name = null;
    ConstructorName constructorName = null;
    InstanceCreationExpression instanceCreation = null;
    if (node is SimpleIdentifier) {
      // name
      name = node as SimpleIdentifier;
      if (name.parent is ConstructorName) {
        constructorName = name.parent as ConstructorName;
        if (constructorName.name == name) {
          // Type.name
          if (constructorName.parent is InstanceCreationExpression) {
            instanceCreation =
                constructorName.parent as InstanceCreationExpression;
            // new Type.name()
            if (instanceCreation.constructorName != constructorName) {
              return;
            }
          }
        }
      }
    }
    // do we have enough information?
    if (instanceCreation == null) {
      return;
    }
    // prepare target interface type
    DartType targetType = constructorName.type.type;
    if (targetType is! InterfaceType) {
      return;
    }
    // prepare location for a new constructor
    ClassElement targetElement = targetType.element as ClassElement;
    AstNode targetTypeNode = getParsedClassElementNode(targetElement);
    if (targetTypeNode is! ClassDeclaration) {
      return;
    }
    ClassMemberLocation targetLocation =
        utils.prepareNewConstructorLocation(targetTypeNode);
    String targetFile = targetElement.source.fullName;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
        builder.write(targetLocation.prefix);
        builder.writeConstructorDeclaration(targetElement.name,
            argumentList: instanceCreation.argumentList,
            constructorName: name,
            constructorNameGroupName: 'NAME');
        builder.write(targetLocation.suffix);
      });
      if (targetFile == file) {
        builder.addLinkedPosition(range.node(name), 'NAME');
      }
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_CONSTRUCTOR,
        args: [constructorName]);
  }

  Future<void> _addFix_createConstructorSuperExplicit() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node.parent is! ConstructorDeclaration ||
        node.parent.parent is! ClassDeclaration) {
      return;
    }
    ConstructorDeclaration targetConstructor =
        node.parent as ConstructorDeclaration;
    ClassDeclaration targetClassNode =
        targetConstructor.parent as ClassDeclaration;
    ClassElement targetClassElement = targetClassNode.declaredElement;
    InterfaceType superType = targetClassElement.supertype;
    // add proposals for all super constructors
    for (ConstructorElement superConstructor in superType.constructors) {
      String constructorName = superConstructor.name;
      // skip private
      if (Identifier.isPrivateName(constructorName)) {
        continue;
      }
      List<ConstructorInitializer> initializers =
          targetConstructor.initializers;
      int insertOffset;
      String prefix;
      if (initializers.isEmpty) {
        insertOffset = targetConstructor.parameters.end;
        prefix = ' : ';
      } else {
        ConstructorInitializer lastInitializer =
            initializers[initializers.length - 1];
        insertOffset = lastInitializer.end;
        prefix = ', ';
      }
      String proposalName = _getConstructorProposalName(superConstructor);
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addInsertion(insertOffset, (DartEditBuilder builder) {
          builder.write(prefix);
          // add super constructor name
          builder.write('super');
          if (!isEmpty(constructorName)) {
            builder.write('.');
            builder.addSimpleLinkedEdit('NAME', constructorName);
          }
          // add arguments
          builder.write('(');
          bool firstParameter = true;
          for (ParameterElement parameter in superConstructor.parameters) {
            // skip non-required parameters
            if (parameter.isOptional) {
              break;
            }
            // comma
            if (firstParameter) {
              firstParameter = false;
            } else {
              builder.write(', ');
            }
            // default value
            builder.addSimpleLinkedEdit(
                parameter.name, getDefaultValueCode(parameter.type));
          }
          builder.write(')');
        });
      });
      _addFixFromBuilder(
          changeBuilder, DartFixKind.ADD_SUPER_CONSTRUCTOR_INVOCATION,
          args: [proposalName]);
    }
  }

  Future<void> _addFix_createConstructorSuperImplicit() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    ClassDeclaration targetClassNode =
        node.getAncestor((parent) => parent is ClassDeclaration);
    ClassElement targetClassElement = targetClassNode.declaredElement;
    InterfaceType superType = targetClassElement.supertype;
    String targetClassName = targetClassElement.name;
    // add proposals for all super constructors
    for (ConstructorElement superConstructor in superType.constructors) {
      superConstructor = ConstructorMember.from(superConstructor, superType);
      String constructorName = superConstructor.name;
      // skip private
      if (Identifier.isPrivateName(constructorName)) {
        continue;
      }
      // prepare parameters and arguments
      Iterable<ParameterElement> requiredParameters = superConstructor
          .parameters
          .where((parameter) => parameter.isNotOptional);
      // add proposal
      ClassMemberLocation targetLocation =
          utils.prepareNewConstructorLocation(targetClassNode);
      String proposalName = _getConstructorProposalName(superConstructor);
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
          void writeParameters(bool includeType) {
            bool firstParameter = true;
            for (ParameterElement parameter in requiredParameters) {
              if (firstParameter) {
                firstParameter = false;
              } else {
                builder.write(', ');
              }
              String parameterName = parameter.displayName;
              if (parameterName.length > 1 && parameterName.startsWith('_')) {
                parameterName = parameterName.substring(1);
              }
              if (includeType && builder.writeType(parameter.type)) {
                builder.write(' ');
              }
              builder.write(parameterName);
            }
          }

          builder.write(targetLocation.prefix);
          builder.write(targetClassName);
          if (!constructorName.isEmpty) {
            builder.write('.');
            builder.addSimpleLinkedEdit('NAME', constructorName);
          }
          builder.write('(');
          writeParameters(true);
          builder.write(') : super');
          if (!constructorName.isEmpty) {
            builder.write('.');
            builder.addSimpleLinkedEdit('NAME', constructorName);
          }
          builder.write('(');
          writeParameters(false);
          builder.write(');');
          builder.write(targetLocation.suffix);
        });
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_CONSTRUCTOR_SUPER,
          args: [proposalName]);
    }
  }

  Future<void> _addFix_createField() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is! SimpleIdentifier) {
      return;
    }
    SimpleIdentifier nameNode = node;
    String name = nameNode.name;
    // prepare target Expression
    Expression target;
    {
      AstNode nameParent = nameNode.parent;
      if (nameParent is PrefixedIdentifier) {
        target = nameParent.prefix;
      } else if (nameParent is PropertyAccess) {
        target = nameParent.realTarget;
      }
    }
    // prepare target ClassElement
    bool staticModifier = false;
    ClassElement targetClassElement;
    if (target != null) {
      // prepare target interface type
      DartType targetType = target.staticType;
      if (targetType is! InterfaceType) {
        return;
      }
      targetClassElement = targetType.element;
      // maybe static
      if (target is Identifier) {
        Identifier targetIdentifier = target;
        Element targetElement = targetIdentifier.staticElement;
        if (targetElement == null) {
          return;
        }
        staticModifier = targetElement.kind == ElementKind.CLASS;
      }
    } else {
      targetClassElement = getEnclosingClassElement(node);
      if (targetClassElement == null) {
        return;
      }
      staticModifier = _inStaticContext();
    }
    if (targetClassElement.librarySource.isInSystemLibrary) {
      return;
    }
    utils.targetClassElement = targetClassElement;
    // prepare target ClassDeclaration
    AstNode targetTypeNode = getParsedClassElementNode(targetClassElement);
    if (targetTypeNode is! ClassDeclaration) {
      return;
    }
    ClassDeclaration targetClassNode = targetTypeNode;
    // prepare location
    ClassMemberLocation targetLocation =
        _getUtilsFor(targetClassNode).prepareNewFieldLocation(targetClassNode);
    // build field source
    Source targetSource = targetClassElement.source;
    String targetFile = targetSource.fullName;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
      Expression fieldTypeNode = climbPropertyAccess(nameNode);
      DartType fieldType = _inferUndefinedExpressionType(fieldTypeNode);
      builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
        builder.write(targetLocation.prefix);
        builder.writeFieldDeclaration(name,
            isStatic: staticModifier,
            nameGroupName: 'NAME',
            type: fieldType,
            typeGroupName: 'TYPE');
        builder.write(targetLocation.suffix);
      });
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_FIELD, args: [name]);
  }

  Future<void> _addFix_createField_initializingFormal() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    //
    // Ensure that we are in an initializing formal parameter.
    //
    FieldFormalParameter parameter =
        node.getAncestor((node) => node is FieldFormalParameter);
    if (parameter == null) {
      return;
    }
    ClassDeclaration targetClassNode =
        parameter.getAncestor((node) => node is ClassDeclaration);
    if (targetClassNode == null) {
      return;
    }
    SimpleIdentifier nameNode = parameter.identifier;
    String name = nameNode.name;
    ClassMemberLocation targetLocation =
        utils.prepareNewFieldLocation(targetClassNode);
    //
    // Add proposal.
    //
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      DartType fieldType = parameter.type?.type;
      builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
        builder.write(targetLocation.prefix);
        builder.writeFieldDeclaration(name,
            nameGroupName: 'NAME', type: fieldType, typeGroupName: 'TYPE');
        builder.write(targetLocation.suffix);
      });
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_FIELD, args: [name]);
  }

  Future<void> _addFix_createFunction_forFunctionType() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is SimpleIdentifier) {
      SimpleIdentifier nameNode = node as SimpleIdentifier;
      // prepare argument expression (to get parameter)
      ClassElement targetElement;
      Expression argument;
      {
        Expression target = getQualifiedPropertyTarget(node);
        if (target != null) {
          DartType targetType = target.staticType;
          if (targetType != null && targetType.element is ClassElement) {
            targetElement = targetType.element as ClassElement;
            argument = target.parent as Expression;
          } else {
            return;
          }
        } else {
          ClassDeclaration enclosingClass =
              node.getAncestor((node) => node is ClassDeclaration);
          targetElement = enclosingClass?.declaredElement;
          argument = nameNode;
        }
      }
      argument = stepUpNamedExpression(argument);
      // should be argument of some invocation
      ParameterElement parameterElement = argument.staticParameterElement;
      if (parameterElement == null) {
        return;
      }
      // should be parameter of function type
      DartType parameterType = parameterElement.type;
      if (parameterType is InterfaceType && parameterType.isDartCoreFunction) {
        ExecutableElement element = new MethodElementImpl('', -1);
        parameterType = new FunctionTypeImpl(element);
      }
      if (parameterType is! FunctionType) {
        return;
      }
      FunctionType functionType = parameterType as FunctionType;
      // add proposal
      if (targetElement != null) {
        await _addProposal_createFunction_method(targetElement, functionType);
      } else {
        await _addProposal_createFunction_function(functionType);
      }
    }
  }

  Future<void> _addFix_createGetter() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is! SimpleIdentifier) {
      return;
    }
    SimpleIdentifier nameNode = node;
    String name = nameNode.name;
    if (!nameNode.inGetterContext()) {
      return;
    }
    // prepare target Expression
    Expression target;
    {
      AstNode nameParent = nameNode.parent;
      if (nameParent is PrefixedIdentifier) {
        target = nameParent.prefix;
      } else if (nameParent is PropertyAccess) {
        target = nameParent.realTarget;
      }
    }
    // prepare target ClassElement
    bool staticModifier = false;
    ClassElement targetClassElement;
    if (target != null) {
      // prepare target interface type
      DartType targetType = target.staticType;
      if (targetType is! InterfaceType) {
        return;
      }
      targetClassElement = targetType.element;
      // maybe static
      if (target is Identifier) {
        Identifier targetIdentifier = target;
        Element targetElement = targetIdentifier.staticElement;
        staticModifier = targetElement?.kind == ElementKind.CLASS;
      }
    } else {
      targetClassElement = getEnclosingClassElement(node);
      if (targetClassElement == null) {
        return;
      }
      staticModifier = _inStaticContext();
    }
    if (targetClassElement.librarySource.isInSystemLibrary) {
      return;
    }
    utils.targetClassElement = targetClassElement;
    // prepare target ClassDeclaration
    AstNode targetTypeNode = getParsedClassElementNode(targetClassElement);
    if (targetTypeNode is! ClassDeclaration) {
      return;
    }
    ClassDeclaration targetClassNode = targetTypeNode;
    // prepare location
    ClassMemberLocation targetLocation =
        _getUtilsFor(targetClassNode).prepareNewGetterLocation(targetClassNode);
    // build method source
    Source targetSource = targetClassElement.source;
    String targetFile = targetSource.fullName;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(targetFile, (DartFileEditBuilder builder) {
      builder.addInsertion(targetLocation.offset, (DartEditBuilder builder) {
        Expression fieldTypeNode = climbPropertyAccess(nameNode);
        DartType fieldType = _inferUndefinedExpressionType(fieldTypeNode);
        builder.write(targetLocation.prefix);
        builder.writeGetterDeclaration(name,
            isStatic: staticModifier,
            nameGroupName: 'NAME',
            returnType: fieldType,
            returnTypeGroupName: 'TYPE');
        builder.write(targetLocation.suffix);
      });
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_GETTER, args: [name]);
  }

  Future<void> _addFix_createImportUri() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // TODO(brianwilkerson) Generalize this to allow other valid string literals.
    // TODO(brianwilkerson) Support the case where the node's parent is a Configuration.
    if (node is SimpleStringLiteral && node.parent is ImportDirective) {
      ImportDirective importDirective = node.parent;
      Source source = importDirective.uriSource;
      if (source != null) {
        String file = source.fullName;
        if (isAbsolute(file) && AnalysisEngine.isDartFileName(file)) {
          String libName = _computeLibraryName(file);
          try {
            DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
            await changeBuilder.addFileEdit(source.fullName,
                (DartFileEditBuilder builder) {
              builder.addSimpleInsertion(0, 'library $libName;$eol$eol');
            });
            _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_FILE,
                args: [source.shortName]);
          } on AnalysisException {
            // Ignore the exception and just don't create a fix.
          }
        }
      }
    }
  }

  Future<void> _addFix_createLocalVariable() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is! SimpleIdentifier) {
      return;
    }
    SimpleIdentifier nameNode = node;
    String name = nameNode.name;
    // if variable is assigned, convert assignment into declaration
    if (node.parent is AssignmentExpression) {
      AssignmentExpression assignment = node.parent;
      if (assignment.leftHandSide == node &&
          assignment.operator.type == TokenType.EQ &&
          assignment.parent is ExpressionStatement) {
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          builder.addSimpleInsertion(node.offset, 'var ');
        });
        _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_LOCAL_VARIABLE,
            args: [name]);
        return;
      }
    }
    // prepare target Statement
    Statement target = node.getAncestor((x) => x is Statement);
    if (target == null) {
      return;
    }
    String prefix = utils.getNodePrefix(target);
    // compute type
    DartType type = _inferUndefinedExpressionType(node);
    if (!(type == null ||
        type is InterfaceType ||
        type is FunctionType &&
            type.element != null &&
            !type.element.isSynthetic)) {
      return;
    }
    // build variable declaration source
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addInsertion(target.offset, (DartEditBuilder builder) {
        builder.writeLocalVariableDeclaration(name,
            nameGroupName: 'NAME', type: type, typeGroupName: 'TYPE');
        builder.write(eol);
        builder.write(prefix);
      });
      builder.addLinkedPosition(range.node(node), 'NAME');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_LOCAL_VARIABLE,
        args: [name]);
  }

  Future<void> _addFix_createMissingOverrides() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node.parent is! ClassDeclaration) {
      return;
    }
    ClassDeclaration targetClass = node.parent as ClassDeclaration;
    ClassElement targetClassElement = targetClass.declaredElement;
    utils.targetClassElement = targetClassElement;
    List<ExecutableElement> elements =
        InheritanceOverrideVerifier.missingOverrides(targetClass).toList();
    // sort by name, getters before setters
    elements.sort((Element a, Element b) {
      int names = compareStrings(a.displayName, b.displayName);
      if (names != 0) {
        return names;
      }
      if (a.kind == ElementKind.GETTER) {
        return -1;
      }
      return 1;
    });
    int numElements = elements.length;

    ClassMemberLocation location =
        utils.prepareNewClassMemberLocation(targetClass, (_) => true);

    String prefix = utils.getIndent(1);
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addInsertion(location.offset, (DartEditBuilder builder) {
        // TODO(brianwilkerson) Compare with builder.writeOverrideOfInheritedMember
        // The builder method doesn't merge getter/setter pairs into fields.

        // Separator management.
        int numOfMembersWritten = 0;
        void addSeparatorBetweenDeclarations() {
          if (numOfMembersWritten == 0) {
            builder.write(location.prefix);
          } else {
            builder.write(eol); // after the previous member
            builder.write(eol); // empty line separator
            builder.write(prefix);
          }
          numOfMembersWritten++;
        }

        // merge getter/setter pairs into fields
        for (int i = 0; i < elements.length; i++) {
          ExecutableElement element = elements[i];
          if (element.kind == ElementKind.GETTER && i + 1 < elements.length) {
            ExecutableElement nextElement = elements[i + 1];
            if (nextElement.kind == ElementKind.SETTER) {
              // remove this and the next elements, adjust iterator
              elements.removeAt(i + 1);
              elements.removeAt(i);
              i--;
              numElements--;
              // separator
              addSeparatorBetweenDeclarations();
              // @override
              builder.write('@override');
              builder.write(eol);
              // add field
              builder.write(prefix);
              builder.writeType(element.type.returnType, required: true);
              builder.write(' ');
              builder.write(element.name);
              builder.write(';');
            }
          }
        }
        // add elements
        for (ExecutableElement element in elements) {
          addSeparatorBetweenDeclarations();
          _addFix_createMissingOverridesForBuilder(
              builder, targetClass, element);
        }
        builder.write(location.suffix);
      });
    });
    changeBuilder.setSelection(new Position(file, location.offset));
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_MISSING_OVERRIDES,
        args: [numElements]);
  }

  void _addFix_createMissingOverridesForBuilder(DartEditBuilder builder,
      ClassDeclaration targetClass, ExecutableElement element) {
    utils.targetExecutableElement = element;
    // prepare environment
    String prefix = utils.getIndent(1);
    String prefix2 = utils.getIndent(2);
    // may be property
    ElementKind elementKind = element.kind;
    bool isGetter = elementKind == ElementKind.GETTER;
    bool isSetter = elementKind == ElementKind.SETTER;
    bool isMethod = elementKind == ElementKind.METHOD;
    bool isOperator = isMethod && (element as MethodElement).isOperator;
    if (isGetter) {
      builder.write('// TODO: implement ${element.displayName}');
      builder.write(eol);
      builder.write(prefix);
    }
    // @override
    builder.write('@override');
    builder.write(eol);
    builder.write(prefix);
    // return type
    if (!isSetter) {
      if (builder.writeType(element.type.returnType,
          methodBeingCopied: element)) {
        builder.write(' ');
      }
    }
    // keyword
    if (isGetter) {
      builder.write('get ');
    } else if (isSetter) {
      builder.write('set ');
    } else if (isOperator) {
      builder.write('operator ');
    }
    // name
    builder.write(element.displayName);
    builder.writeTypeParameters(element.typeParameters,
        methodBeingCopied: element);
    // parameters + body
    if (isGetter) {
      builder.write(' => null;');
    } else {
      List<ParameterElement> parameters = element.parameters;
      builder.writeParameters(parameters, methodBeingCopied: element);
      builder.write(' {');
      // TO-DO
      builder.write(eol);
      builder.write(prefix2);
      builder.write('// TODO: implement ${element.displayName}');
      builder.write(eol);
      // close method
      builder.write(prefix);
      builder.write('}');
    }
    utils.targetExecutableElement = null;
  }

  Future<void> _addFix_createMixin() async {
    Element prefixElement = null;
    String name = null;
    SimpleIdentifier nameNode;
    if (node is SimpleIdentifier) {
      AstNode parent = node.parent;
      if (parent is PrefixedIdentifier) {
        if (parent.parent is InstanceCreationExpression) {
          return;
        }
        PrefixedIdentifier prefixedIdentifier = parent;
        prefixElement = prefixedIdentifier.prefix.staticElement;
        if (prefixElement == null) {
          return;
        }
        parent = prefixedIdentifier.parent;
        nameNode = prefixedIdentifier.identifier;
        name = prefixedIdentifier.identifier.name;
      } else if (parent is TypeName &&
          parent.parent is ConstructorName &&
          parent.parent.parent is InstanceCreationExpression) {
        return;
      } else {
        nameNode = node;
        name = nameNode.name;
      }
      if (!_mayBeTypeIdentifier(nameNode)) {
        return;
      }
    } else {
      return;
    }
    // prepare environment
    Element targetUnit;
    String prefix = '';
    String suffix = '';
    int offset = -1;
    String filePath;
    if (prefixElement == null) {
      targetUnit = unitElement;
      CompilationUnitMember enclosingMember = node.getAncestor((node) =>
          node is CompilationUnitMember && node.parent is CompilationUnit);
      if (enclosingMember == null) {
        return;
      }
      offset = enclosingMember.end;
      filePath = file;
      prefix = '$eol$eol';
    } else {
      for (ImportElement import in unitLibraryElement.imports) {
        if (prefixElement is PrefixElement && import.prefix == prefixElement) {
          LibraryElement library = import.importedLibrary;
          if (library != null) {
            targetUnit = library.definingCompilationUnit;
            Source targetSource = targetUnit.source;
            try {
              offset = targetSource.contents.data.length;
              filePath = targetSource.fullName;
              prefix = '$eol';
              suffix = '$eol';
            } on FileSystemException {
              // If we can't read the file to get the offset, then we can't
              // create a fix.
            }
            break;
          }
        }
      }
    }
    if (offset < 0) {
      return;
    }
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(filePath, (DartFileEditBuilder builder) {
      builder.addInsertion(offset, (DartEditBuilder builder) {
        builder.write(prefix);
        builder.writeMixinDeclaration(name, nameGroupName: 'NAME');
        builder.write(suffix);
      });
      if (prefixElement == null) {
        builder.addLinkedPosition(range.node(node), 'NAME');
      }
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_MIXIN, args: [name]);
  }

  Future<void> _addFix_createNoSuchMethod() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node.parent is! ClassDeclaration) {
      return;
    }
    ClassDeclaration targetClass = node.parent as ClassDeclaration;
    // prepare environment
    String prefix = utils.getIndent(1);
    int insertOffset = targetClass.end - 1;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addInsertion(insertOffset, (DartEditBuilder builder) {
        builder.selectHere();
        // insert empty line before existing member
        if (!targetClass.members.isEmpty) {
          builder.write(eol);
        }
        // append method
        builder.write(prefix);
        builder.write(
            'noSuchMethod(Invocation invocation) => super.noSuchMethod(invocation);');
        builder.write(eol);
      });
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_NO_SUCH_METHOD);
  }

  Future<void> _addFix_createPartUri() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // TODO(brianwilkerson) Generalize this to allow other valid string literals.
    if (node is SimpleStringLiteral && node.parent is PartDirective) {
      PartDirective partDirective = node.parent;
      Source source = partDirective.uriSource;
      if (source != null) {
        String libName = unitLibraryElement.name;
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(source.fullName,
            (DartFileEditBuilder builder) {
          // TODO(brianwilkerson) Consider using the URI rather than name
          builder.addSimpleInsertion(0, 'part of $libName;$eol$eol');
        });
        _addFixFromBuilder(changeBuilder, DartFixKind.CREATE_FILE,
            args: [source.shortName]);
      }
    }
  }

  Future<void> _addFix_illegalAsyncReturnType() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // prepare the existing type
    TypeAnnotation typeName = node.getAncestor((n) => n is TypeAnnotation);
    TypeProvider typeProvider = this.typeProvider;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.replaceTypeWithFuture(typeName, typeProvider);
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.REPLACE_RETURN_TYPE_FUTURE);
  }

  Future<void> _addFix_importLibrary(FixKind kind, Uri library) async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    String uriText;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      uriText = builder.importLibrary(library);
    });
    _addFixFromBuilder(changeBuilder, kind, args: [uriText]);
  }

  Future<void> _addFix_importLibrary_withElement(String name,
      List<ElementKind> elementKinds, TopLevelDeclarationKind kind2) async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // ignore if private
    if (name.startsWith('_')) {
      return;
    }
    // may be there is an existing import,
    // but it is with prefix and we don't use this prefix
    Set<Source> alreadyImportedWithPrefix = new Set<Source>();
    for (ImportElement imp in unitLibraryElement.imports) {
      // prepare element
      LibraryElement libraryElement = imp.importedLibrary;
      Element element = getExportedElement(libraryElement, name);
      if (element == null) {
        continue;
      }
      if (element is PropertyAccessorElement) {
        element = (element as PropertyAccessorElement).variable;
      }
      if (!elementKinds.contains(element.kind)) {
        continue;
      }
      // may be apply prefix
      PrefixElement prefix = imp.prefix;
      if (prefix != null) {
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          builder.addSimpleReplacement(
              range.startLength(node, 0), '${prefix.displayName}.');
        });
        _addFixFromBuilder(changeBuilder, DartFixKind.IMPORT_LIBRARY_PREFIX,
            args: [libraryElement.displayName, prefix.displayName]);
        continue;
      }
      // may be update "show" directive
      List<NamespaceCombinator> combinators = imp.combinators;
      if (combinators.length == 1 && combinators[0] is ShowElementCombinator) {
        ShowElementCombinator showCombinator =
            combinators[0] as ShowElementCombinator;
        // prepare new set of names to show
        Set<String> showNames = new SplayTreeSet<String>();
        showNames.addAll(showCombinator.shownNames);
        showNames.add(name);
        // prepare library name - unit name or 'dart:name' for SDK library
        String libraryName =
            libraryElement.definingCompilationUnit.source.uri.toString();
        if (libraryElement.isInSdk) {
          libraryName = libraryElement.source.shortName;
        }
        // don't add this library again
        alreadyImportedWithPrefix.add(libraryElement.source);
        // update library
        String newShowCode = 'show ${showNames.join(', ')}';
        int offset = showCombinator.offset;
        int length = showCombinator.end - offset;
        String libraryFile = unitLibraryElement.source.fullName;
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(libraryFile,
            (DartFileEditBuilder builder) {
          builder.addSimpleReplacement(
              new SourceRange(offset, length), newShowCode);
        });
        _addFixFromBuilder(changeBuilder, DartFixKind.IMPORT_LIBRARY_SHOW,
            args: [libraryName]);
      }
    }
    // Find new top-level declarations.
    {
      List<TopLevelDeclarationInSource> declarations =
          await getTopLevelDeclarations(name);
      for (TopLevelDeclarationInSource declaration in declarations) {
        // Check the kind.
        if (declaration.declaration.kind != kind2) {
          continue;
        }
        // Check the source.
        Source librarySource = declaration.source;
        if (alreadyImportedWithPrefix.contains(librarySource)) {
          continue;
        }
        if (!_isSourceVisibleToLibrary(librarySource)) {
          continue;
        }
        // Compute the fix kind.
        FixKind fixKind;
        if (librarySource.isInSystemLibrary) {
          fixKind = DartFixKind.IMPORT_LIBRARY_SDK;
        } else if (_isLibSrcPath(librarySource.fullName)) {
          // Bad: non-API.
          fixKind = DartFixKind.IMPORT_LIBRARY_PROJECT3;
        } else if (declaration.isExported) {
          // Ugly: exports.
          fixKind = DartFixKind.IMPORT_LIBRARY_PROJECT2;
        } else {
          // Good: direct declaration.
          fixKind = DartFixKind.IMPORT_LIBRARY_PROJECT1;
        }
        // Add the fix.
        await _addFix_importLibrary(fixKind, librarySource.uri);
      }
    }
  }

  Future<void> _addFix_importLibrary_withFunction() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is SimpleIdentifier && node.parent is MethodInvocation) {
      MethodInvocation invocation = node.parent as MethodInvocation;
      if (invocation.realTarget == null && invocation.methodName == node) {
        String name = (node as SimpleIdentifier).name;
        await _addFix_importLibrary_withElement(name,
            const [ElementKind.FUNCTION], TopLevelDeclarationKind.function);
      }
    }
  }

  Future<void> _addFix_importLibrary_withTopLevelVariable() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is SimpleIdentifier) {
      String name = (node as SimpleIdentifier).name;
      await _addFix_importLibrary_withElement(
          name,
          const [ElementKind.TOP_LEVEL_VARIABLE],
          TopLevelDeclarationKind.variable);
    }
  }

  Future<void> _addFix_importLibrary_withType() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (_mayBeTypeIdentifier(node)) {
      String typeName = (node as SimpleIdentifier).name;
      await _addFix_importLibrary_withElement(
          typeName,
          const [ElementKind.CLASS, ElementKind.FUNCTION_TYPE_ALIAS],
          TopLevelDeclarationKind.type);
    } else if (_mayBeImplicitConstructor(node)) {
      String typeName = (node as SimpleIdentifier).name;
      await _addFix_importLibrary_withElement(
          typeName, const [ElementKind.CLASS], TopLevelDeclarationKind.type);
    }
  }

  Future<void> _addFix_insertSemicolon() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (error.message.contains("';'")) {
      if (_isAwaitNode()) {
        return;
      }
      int insertOffset = error.offset + error.length;
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addSimpleInsertion(insertOffset, ';');
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.INSERT_SEMICOLON);
    }
  }

  Future<void> _addFix_isNotEmpty() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is! PrefixExpression) {
      return;
    }
    PrefixExpression prefixExpression = node;
    Token negation = prefixExpression.operator;
    if (negation.type != TokenType.BANG) {
      return;
    }
    SimpleIdentifier identifier;
    Expression expression = prefixExpression.operand;
    if (expression is PrefixedIdentifier) {
      identifier = expression.identifier;
    } else if (expression is PropertyAccess) {
      identifier = expression.propertyName;
    } else {
      return;
    }
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addDeletion(range.token(negation));
      builder.addSimpleReplacement(range.node(identifier), 'isNotEmpty');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.USE_IS_NOT_EMPTY);
  }

  Future<void> _addFix_isNotNull() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (coveredNode is IsExpression) {
      IsExpression isExpression = coveredNode as IsExpression;
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder
            .addReplacement(range.endEnd(isExpression.expression, isExpression),
                (DartEditBuilder builder) {
          builder.write(' != null');
        });
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.USE_NOT_EQ_NULL);
    }
  }

  Future<void> _addFix_isNull() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (coveredNode is IsExpression) {
      IsExpression isExpression = coveredNode as IsExpression;
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder
            .addReplacement(range.endEnd(isExpression.expression, isExpression),
                (DartEditBuilder builder) {
          builder.write(' == null');
        });
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.USE_EQ_EQ_NULL);
    }
  }

  Future<void> _addFix_makeEnclosingClassAbstract() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    ClassDeclaration enclosingClass =
        node.getAncestor((node) => node is ClassDeclaration);
    if (enclosingClass == null) {
      return;
    }
    String className = enclosingClass.name.name;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleInsertion(
          enclosingClass.classKeyword.offset, 'abstract ');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.MAKE_CLASS_ABSTRACT,
        args: [className]);
  }

  Future<void> _addFix_makeFieldNotFinal() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode node = this.node;
    if (node is SimpleIdentifier &&
        node.staticElement is PropertyAccessorElement) {
      PropertyAccessorElement getter = node.staticElement;
      if (getter.isGetter &&
          getter.isSynthetic &&
          !getter.variable.isSynthetic &&
          getter.variable.setter == null &&
          getter.enclosingElement is ClassElement) {
        AstNode name =
            await astProvider.getParsedNameForElement(getter.variable);
        AstNode variable = name?.parent;
        if (variable is VariableDeclaration &&
            variable.parent is VariableDeclarationList &&
            variable.parent.parent is FieldDeclaration) {
          VariableDeclarationList declarationList = variable.parent;
          Token keywordToken = declarationList.keyword;
          if (declarationList.variables.length == 1 &&
              keywordToken.keyword == Keyword.FINAL) {
            DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
            await changeBuilder.addFileEdit(file,
                (DartFileEditBuilder builder) {
              if (declarationList.type != null) {
                builder.addReplacement(
                    range.startStart(keywordToken, declarationList.type),
                    (DartEditBuilder builder) {});
              } else {
                builder.addReplacement(range.startStart(keywordToken, variable),
                    (DartEditBuilder builder) {
                  builder.write('var ');
                });
              }
            });
            String fieldName = getter.variable.displayName;
            _addFixFromBuilder(changeBuilder, DartFixKind.MAKE_FIELD_NOT_FINAL,
                args: [fieldName]);
          }
        }
      }
    }
  }

  Future<void> _addFix_makeVariableFinal() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode node = this.node;
    if (node is SimpleIdentifier && node.parent is VariableDeclaration) {
      VariableDeclaration declaration = node.parent;
      VariableDeclarationList list = declaration.parent;
      if (list.variables.length == 1) {
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          if (list.keyword == null) {
            builder.addSimpleInsertion(list.offset, 'final ');
          } else if (list.keyword.keyword == Keyword.VAR) {
            builder.addSimpleReplacement(range.token(list.keyword), 'final');
          }
        });
        _addFixFromBuilder(changeBuilder, DartFixKind.MAKE_FINAL);
      }
    }
  }

  Future<void> _addFix_nonBoolCondition_addNotNull() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleInsertion(error.offset + error.length, ' != null');
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.ADD_NE_NULL);
  }

  Future<void> _addFix_removeAwait() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    final awaitExpression = node;
    if (awaitExpression is AwaitExpression) {
      final awaitToken = awaitExpression.awaitKeyword;
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(range.startStart(awaitToken, awaitToken.next));
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_AWAIT);
    }
  }

  Future<void> _addFix_removeDeadCode() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode coveringNode = this.coveredNode;
    if (coveringNode is Expression) {
      AstNode parent = coveredNode.parent;
      if (parent is BinaryExpression) {
        if (parent.rightOperand == coveredNode) {
          DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
          await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
            builder.addDeletion(range.endEnd(parent.leftOperand, coveredNode));
          });
          _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_DEAD_CODE);
        }
      }
    } else if (coveringNode is Block) {
      Block block = coveringNode;
      List<Statement> statementsToRemove = <Statement>[];
      for (Statement statement in block.statements) {
        if (range.node(statement).intersects(errorRange)) {
          statementsToRemove.add(statement);
        }
      }
      if (statementsToRemove.isNotEmpty) {
        SourceRange rangeToRemove =
            utils.getLinesRangeStatements(statementsToRemove);
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          builder.addDeletion(rangeToRemove);
        });
        _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_DEAD_CODE);
      }
    } else if (coveringNode is Statement) {
      SourceRange rangeToRemove =
          utils.getLinesRangeStatements(<Statement>[coveringNode]);
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(rangeToRemove);
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_DEAD_CODE);
    }
  }

  Future<void> _addFix_removeEmptyCatch() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addDeletion(utils.getLinesRange(range.node(node.parent)));
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_EMPTY_CATCH);
  }

  Future<void> _addFix_removeEmptyConstructorBody() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addSimpleReplacement(
          utils.getLinesRange(range.node(node.parent)), ';');
    });
    _addFixFromBuilder(
        changeBuilder, DartFixKind.REMOVE_EMPTY_CONSTRUCTOR_BODY);
  }

  Future<void> _addFix_removeEmptyElse() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    IfStatement ifStatement = node.parent;
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addDeletion(utils.getLinesRange(
          range.startEnd(ifStatement.elseKeyword, ifStatement.elseStatement)));
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_EMPTY_ELSE);
  }

  Future<void> _addFix_removeEmptyStatement() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    EmptyStatement emptyStatement = node;
    if (emptyStatement.parent is Block) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(utils.getLinesRange(range.node(emptyStatement)));
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_EMPTY_STATEMENT);
    } else {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        Token previous = emptyStatement.findPrevious(emptyStatement.beginToken);
        if (previous != null) {
          builder.addSimpleReplacement(
              range.endEnd(previous, emptyStatement), ' {}');
        }
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REPLACE_WITH_BRACKETS);
    }
  }

  Future<void> _addFix_removeInitializer() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    // Retrieve the linted node.
    VariableDeclaration ancestor =
        node.getAncestor((a) => a is VariableDeclaration);
    if (ancestor == null) {
      return;
    }
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addDeletion(range.endEnd(ancestor.name, ancestor.initializer));
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_INITIALIZER);
  }

  Future<void> _addFix_removeInterpolationBraces() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    AstNode node = this.node;
    if (node is InterpolationExpression) {
      Token right = node.rightBracket;
      if (node.expression != null && right != null) {
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          builder.addSimpleReplacement(
              range.startStart(node, node.expression), r'$');
          builder.addDeletion(range.token(right));
        });
        _addFixFromBuilder(
            changeBuilder, DartFixKind.LINT_REMOVE_INTERPOLATION_BRACES);
      } else {}
    }
  }

  Future<void> _addFix_removeMethodDeclaration() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    MethodDeclaration declaration =
        node.getAncestor((node) => node is MethodDeclaration);
    if (declaration != null) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(utils.getLinesRange(range.node(declaration)));
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_METHOD_DECLARATION);
    }
  }

  Future<void> _addFix_removeParameters_inGetterDeclaration() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is MethodDeclaration) {
      // Support for the analyzer error.
      MethodDeclaration method = node as MethodDeclaration;
      SimpleIdentifier name = method.name;
      FunctionBody body = method.body;
      if (name != null && body != null) {
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          builder.addSimpleReplacement(range.endStart(name, body), ' ');
        });
        _addFixFromBuilder(
            changeBuilder, DartFixKind.REMOVE_PARAMETERS_IN_GETTER_DECLARATION);
      }
    } else if (node is FormalParameterList) {
      // Support for the fasta error.
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(range.node(node));
      });
      _addFixFromBuilder(
          changeBuilder, DartFixKind.REMOVE_PARAMETERS_IN_GETTER_DECLARATION);
    }
  }

  Future<void> _addFix_removeParentheses_inGetterInvocation() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is SimpleIdentifier && node.parent is MethodInvocation) {
      MethodInvocation invocation = node.parent as MethodInvocation;
      if (invocation.methodName == node && invocation.target != null) {
        DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
        await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
          builder.addDeletion(range.endEnd(node, invocation));
        });
        _addFixFromBuilder(
            changeBuilder, DartFixKind.REMOVE_PARENTHESIS_IN_GETTER_INVOCATION);
      }
    }
  }

  Future<void> _addFix_removeThisExpression() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    final thisExpression = node is ThisExpression
        ? node
        : node.getAncestor((node) => node is ThisExpression);
    final parent = thisExpression?.parent;
    if (parent is PropertyAccess) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(range.startEnd(parent, parent.operator));
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_THIS_EXPRESSION);
    } else if (parent is MethodInvocation) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(range.startEnd(parent, parent.operator));
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_THIS_EXPRESSION);
    }
  }

  Future<void> _addFix_removeTypeAnnotation() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    final TypeAnnotation type =
        node.getAncestor((node) => node is TypeAnnotation);
    if (type != null) {
      DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
      await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
        builder.addDeletion(range.startStart(type, type.endToken.next));
      });
      _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_TYPE_NAME);
    }
  }

  Future<void> _addFix_removeUnnecessaryCast() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (coveredNode is! AsExpression) {
      return;
    }
    AsExpression asExpression = coveredNode as AsExpression;
    Expression expression = asExpression.expression;
    int expressionPrecedence = getExpressionPrecedence(expression);
    // remove 'as T' from 'e as T'
    DartChangeBuilder changeBuilder = new DartChangeBuilder(session);
    await changeBuilder.addFileEdit(file, (DartFileEditBuilder builder) {
      builder.addDeletion(range.endEnd(expression, asExpression));
      _removeEnclosingParentheses(builder, asExpression, expressionPrecedence);
    });
    _addFixFromBuilder(changeBuilder, DartFixKind.REMOVE_UNNECESSARY_CAST);
  }

  Future<void> _addFix_removeUnusedCatchClause() async {
    // TODO(brianwilkerson) Determine whether this await is necessary.
    await null;
    if (node is SimpleIdentifier) {
      AstNode catchClause = node.parent;
      if (catchClause is