| // Copyright (c) 2019, 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 'package:analyzer/dart/ast/ast.dart'; |
| import 'package:analyzer/dart/ast/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| import 'package:linter/src/analyzer.dart'; |
| |
| const _desc = r'Prefer is! operator.'; |
| |
| const _details = r''' |
| When checking if the object has not specified type, it is preferable to use 'is!' operator. |
| |
| **BAD:** |
| ``` |
| if (!(foo is Foo)) { |
| ... |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| if (foo is! Foo) { |
| ... |
| } |
| ``` |
| |
| '''; |
| |
| class PreferIsNotOperator extends LintRule implements NodeLintRule { |
| PreferIsNotOperator() |
| : super( |
| name: 'prefer_is_not_operator', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| final visitor = _Visitor(this); |
| registry.addIsExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitIsExpression(IsExpression node) { |
| // Return if it is `is!` expression |
| if (node.notOperator != null) { |
| return; |
| } |
| |
| // Check whether is expression is inside parenthesis |
| if (node.parent is ParenthesizedExpression) { |
| final parenthesizedExpression = node.parent; |
| final prefixExpression = parenthesizedExpression.parent; |
| // Check for NOT (!) operator |
| if (prefixExpression is PrefixExpression && |
| prefixExpression.operator.type == TokenType.BANG) { |
| rule.reportLint(parenthesizedExpression.parent); |
| } |
| } |
| } |
| } |