anchor.diff:  import 'package:analyzer/dart/ast/ast.dart';
   import 'package:analyzer/dart/ast/token.dart';
   import 'package:analyzer/dart/ast/visitor.dart';
  +import 'package:analyzer/src/dart/error/lint_codes.dart';
   import 'package:linter/src/analyzer.dart';
   
   const _desc = r'Declare method return types.';
  
positive.code: }
  
  class _Visitor extends SimpleAstVisitor<void> {
    final LintRule rule;
  
    _Visitor(this.rule);
  
negative.code:   @override
    void visitFunctionDeclaration(FunctionDeclaration node) {
      if (!node.isSetter && node.returnType == null) {
        rule.reportLint(node.name,
            arguments: [node.name.name], errorCode: functionCode);
      }
    }
  
    @override
    void visitFunctionTypeAlias(FunctionTypeAlias node) {
      if (node.returnType == null) {
        rule.reportLint(node.name,
            arguments: [node.name.name], errorCode: functionCode);
      }
    }
  
  