| // Copyright (c) 2015, 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/visitor.dart'; |
| |
| import '../analyzer.dart'; |
| |
| const _desc = r'Avoid using `as`.'; |
| |
| const _details = r''' |
| |
| **AVOID** using `as`. |
| |
| If you know the type is correct, use an assertion or assign to a more |
| narrowly-typed variable (this avoids the type check in release mode; `as` is not |
| compiled out in release mode). If you don't know whether the type is |
| correct, check using `is` (this avoids the exception that `as` raises). |
| |
| **BAD:** |
| ```dart |
| (pm as Person).firstName = 'Seth'; |
| ``` |
| |
| **GOOD:** |
| ```dart |
| if (pm is Person) |
| pm.firstName = 'Seth'; |
| ``` |
| |
| but certainly not |
| |
| **BAD:** |
| ```dart |
| try { |
| (pm as Person).firstName = 'Seth'; |
| } on CastError { } |
| ``` |
| |
| Note that an exception is made in the case of `dynamic` since the cast has no |
| performance impact. |
| |
| **OK:** |
| ```dart |
| HasScrollDirection scrollable = renderObject as dynamic; |
| ``` |
| |
| |
| **DEPRECATED:** This advice is no longer recommended. |
| |
| The rule will be removed in a future Linter release. |
| '''; |
| |
| class AvoidAs extends LintRule implements NodeLintRule { |
| AvoidAs() |
| : super( |
| name: 'avoid_as', |
| description: _desc, |
| details: _details, |
| group: Group.style, |
| maturity: Maturity.deprecated, |
| ); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addAsExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitAsExpression(AsExpression node) { |
| var typeAnnotation = node.type; |
| if (typeAnnotation is NamedType && typeAnnotation.name.name != 'dynamic') { |
| rule.reportLint(typeAnnotation); |
| } |
| } |
| } |