| // Copyright (c) 2020, 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 '../analyzer.dart'; |
| |
| const _desc = |
| r'Prefer intValue.isOdd/isEven instead of checking the result of % 2.'; |
| |
| const _details = r''' |
| |
| **PREFER** the use of intValue.isOdd/isEven to check for evenness. |
| |
| **BAD:** |
| ``` |
| bool isEven = 1 % 2 == 0; |
| bool isOdd = 13 % 2 == 1; |
| ``` |
| |
| **GOOD:** |
| ``` |
| bool isEven = 1.isEven; |
| bool isOdd = 13.isOdd; |
| ``` |
| |
| '''; |
| |
| class UseIsEvenRatherThanModuloCheck extends LintRule implements NodeLintRule { |
| UseIsEvenRatherThanModuloCheck() |
| : super( |
| name: 'use_is_even_rather_than_modulo', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| void registerNodeProcessors(NodeLintRegistry registry, |
| [LinterContext context]) { |
| final visitor = _Visitor(this); |
| registry.addBinaryExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| _Visitor(this.rule); |
| |
| @override |
| void visitBinaryExpression(BinaryExpression node) { |
| // This lint error only happens when the operator is equality. |
| if (node.operator.type != TokenType.EQ_EQ) { |
| return; |
| } |
| var left = node.leftOperand; |
| var leftType = left.staticType; |
| var right = node.rightOperand; |
| var rightType = right.staticType; |
| // Both sides have to have static type of int |
| if (!(right is IntegerLiteral && |
| leftType.isDartCoreInt == true && |
| rightType.isDartCoreInt == true)) { |
| return; |
| } |
| // The left side expression has to be modulo by 2 type. |
| if (left is BinaryExpression) { |
| var rightChild = left.rightOperand; |
| var rightChildType = rightChild.staticType; |
| if (left.operator.type == TokenType.PERCENT && |
| rightChild is IntegerLiteral && |
| rightChild.value == 2 && |
| rightChildType.isDartCoreInt == true) { |
| rule.reportLint(node); |
| } |
| } |
| } |
| } |