anchor.diff:  import 'package:analyzer/src/dart/element/inheritance_manager3.dart';
   import 'package:analyzer/src/generated/resolver.dart';
   import 'package:analyzer/src/generated/source.dart';
  -import 'package:analyzer/src/generated/testing/test_type_provider.dart';
  +import 'package:analyzer/src/test_utilities/find_node.dart';
   import 'package:analyzer_plugin/protocol/protocol_common.dart';
   import 'package:analyzer_plugin/src/utilities/change_builder/change_builder_dart.dart';
   import 'package:analyzer_plugin/utilities/change_builder/change_builder_core.dart';
  
positive.code:     String path = convertPath('/home/test/lib/test.dart');
      addSource(path, 'String f() {}');
  
      CompilationUnit unit = (await driver.getResult(path))?.unit;
      FunctionDeclaration function = unit.declarations[0] as FunctionDeclaration;
      FunctionBody body = function.functionExpression.body;
  
      DartChangeBuilderImpl builder = newBuilder();
      await builder.addFileEdit(path, (FileEditBuilder builder) {
        (builder as DartFileEditBuilder)
            .convertFunctionFromSyncToAsync(body, typeProvider);
      });
      List<SourceEdit> edits = getEdits(builder);
      expect(edits, hasLength(2));
  
negative.code:     String path = convertPath('/home/test/lib/test.dart');
      addSource(path, 'String f() {}');
  
      var resolvedUnit = await driver.getResult(path);
      var findNode = FindNode(resolvedUnit.content, resolvedUnit.unit);
      var type = findNode.typeAnnotation('String');
  
      DartChangeBuilderImpl builder = newBuilder();
      await builder.addFileEdit(path, (FileEditBuilder builder) {
        (builder as DartFileEditBuilder)
            .replaceTypeWithFuture(type, resolvedUnit.typeProvider);
      });
      List<SourceEdit> edits = getEdits(builder);
      expect(edits, hasLength(1));
  