| // Copyright (c) 2024, 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'Use truncating division.'; |
| |
| const _details = r''' |
| **DO** use truncating division, '~/', instead of regular division ('/') followed |
| by 'toInt()'. |
| |
| Dart features a "truncating division" operator which is the same operation as |
| division followed by truncation, but which is more concise and expressive, and |
| may be more performant on some platforms, for certain inputs. |
| |
| **BAD:** |
| ```dart |
| var x = (2 / 3).toInt(); |
| ``` |
| |
| **GOOD:** |
| ```dart |
| var x = 2 ~/ 3; |
| ``` |
| |
| '''; |
| |
| class UseTruncatingDivision extends LintRule { |
| static const LintCode code = LintCode( |
| 'use_truncating_division', |
| 'Use truncating division.', |
| correctionMessage: |
| "Try using truncating division, '~/', instead of regular division " |
| "('/') followed by 'toInt()'.", |
| ); |
| |
| UseTruncatingDivision() |
| : super( |
| name: 'use_truncating_division', |
| description: _desc, |
| details: _details, |
| categories: {LintRuleCategory.languageFeatureUsage}); |
| |
| @override |
| LintCode get lintCode => code; |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addBinaryExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitBinaryExpression(BinaryExpression node) { |
| if (node.operator.type != TokenType.SLASH) return; |
| |
| // Return if the two operands are not each `int`. |
| var leftType = node.leftOperand.staticType; |
| if (leftType == null || !leftType.isDartCoreInt) return; |
| |
| var rightType = node.rightOperand.staticType; |
| if (rightType == null || !rightType.isDartCoreInt) return; |
| |
| // Return if the '/' operator is not defined in core, or if we don't know |
| // its static type. |
| var methodElement = node.staticElement; |
| if (methodElement == null) return; |
| |
| var libraryElement = methodElement.library; |
| if (!libraryElement.isDartCore) return; |
| |
| var parent = node.parent; |
| if (parent is! ParenthesizedExpression) return; |
| |
| var outermostParentheses = parent.thisOrAncestorMatching( |
| (e) => e.parent is! ParenthesizedExpression)! |
| as ParenthesizedExpression; |
| var grandParent = outermostParentheses.parent; |
| if (grandParent is MethodInvocation && |
| grandParent.methodName.name == 'toInt' && |
| grandParent.argumentList.arguments.isEmpty) { |
| rule.reportLint(grandParent); |
| } |
| } |
| } |