| // Copyright (c) 2016, 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/standard_resolution_map.dart'; |
| import 'package:analyzer/dart/ast/token.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| import 'package:linter/src/analyzer.dart'; |
| import 'package:linter/src/util/dart_type_utilities.dart'; |
| |
| const _desc = |
| r'Equality operator `==` invocation with references of unrelated types.'; |
| |
| const _details = r''' |
| |
| **DON'T** Compare references of unrelated types for equality. |
| |
| Comparing references of a type where neither is a subtype of the other most |
| likely will return `false` and might not reflect programmer's intent. |
| |
| **BAD:** |
| ``` |
| void someFunction() { |
| var x = '1'; |
| if (x == 1) print('someFunction'); // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void someFunction1() { |
| String x = '1'; |
| if (x == 1) print('someFunction1'); // LINT |
| } |
| ``` |
| |
| **BAD:** |
| ``` |
| void someFunction13(DerivedClass2 instance) { |
| var other = new DerivedClass3(); |
| |
| if (other == instance) print('someFunction13'); // LINT |
| } |
| |
| class ClassBase {} |
| |
| class DerivedClass1 extends ClassBase {} |
| |
| abstract class Mixin {} |
| |
| class DerivedClass2 extends ClassBase with Mixin {} |
| |
| class DerivedClass3 extends ClassBase implements Mixin {} |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction2() { |
| var x = '1'; |
| var y = '2'; |
| if (x == y) print(someFunction2); // OK |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction3() { |
| for (var i = 0; i < 10; i++) { |
| if (i == 0) print(someFunction3); // OK |
| } |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction4() { |
| var x = '1'; |
| if (x == null) print(someFunction4); // OK |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction7() { |
| List someList; |
| |
| if (someList.length == 0) print('someFunction7'); // OK |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction8(ClassBase instance) { |
| DerivedClass1 other; |
| |
| if (other == instance) print('someFunction8'); // OK |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction10(unknown) { |
| var what = unknown - 1; |
| for (var index = 0; index < unknown; index++) { |
| if (what == index) print('someFunction10'); // OK |
| } |
| } |
| ``` |
| |
| **GOOD:** |
| ``` |
| void someFunction11(Mixin instance) { |
| var other = new DerivedClass2(); |
| |
| if (other == instance) print('someFunction11'); // OK |
| if (other != instance) print('!someFunction11'); // OK |
| } |
| |
| class ClassBase {} |
| |
| abstract class Mixin {} |
| |
| class DerivedClass2 extends ClassBase with Mixin {} |
| ``` |
| |
| '''; |
| |
| bool _hasNonComparableOperands(BinaryExpression node) => |
| !DartTypeUtilities.isNullLiteral(node.leftOperand) && |
| !DartTypeUtilities.isNullLiteral(node.rightOperand) && |
| DartTypeUtilities.unrelatedTypes( |
| node.leftOperand.bestType, node.rightOperand.bestType); |
| |
| class UnrelatedTypeEqualityChecks extends LintRule { |
| _Visitor _visitor; |
| |
| UnrelatedTypeEqualityChecks() |
| : super( |
| name: 'unrelated_type_equality_checks', |
| description: _desc, |
| details: _details, |
| group: Group.errors) { |
| _visitor = new _Visitor(this); |
| } |
| |
| @override |
| AstVisitor getVisitor() => _visitor; |
| } |
| |
| class _Visitor extends SimpleAstVisitor { |
| static const String _dartCoreLibraryName = 'dart.core'; |
| static const String _boolClassName = 'bool'; |
| |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitBinaryExpression(BinaryExpression node) { |
| bool isDartCoreBoolean = |
| resolutionMap.bestTypeForExpression(node).name == _boolClassName && |
| resolutionMap.bestTypeForExpression(node).element?.library?.name == |
| _dartCoreLibraryName; |
| if (!isDartCoreBoolean || |
| (node.operator.type != TokenType.EQ_EQ && |
| node.operator.type != TokenType.BANG_EQ)) { |
| return; |
| } |
| |
| if (_hasNonComparableOperands(node)) { |
| rule.reportLint(node); |
| } |
| } |
| } |