| // Copyright (c) 2018, 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 'package:analyzer/dart/element/element.dart'; |
| |
| import '../analyzer.dart'; |
| |
| const _desc = r'Avoid field initializers in const classes.'; |
| |
| const _details = r''' |
| **AVOID** field initializers in const classes. |
| |
| Instead of `final x = const expr;`, you should write `get x => const expr;` and |
| not allocate a useless field. As of April 2018 this is true for the VM, but not |
| for code that will be compiled to JS. |
| |
| **BAD:** |
| ```dart |
| class A { |
| final a = const []; |
| const A(); |
| } |
| ``` |
| |
| **GOOD:** |
| ```dart |
| class A { |
| get a => const []; |
| const A(); |
| } |
| ``` |
| |
| '''; |
| |
| class AvoidFieldInitializersInConstClasses extends LintRule { |
| static const LintCode code = LintCode( |
| 'avoid_field_initializers_in_const_classes', |
| "Fields in 'const' classes should not have initializers.", |
| correctionMessage: |
| 'Try converting the field to a getter or initialize the field in the ' |
| 'constructors.'); |
| |
| AvoidFieldInitializersInConstClasses() |
| : super( |
| name: 'avoid_field_initializers_in_const_classes', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| LintCode get lintCode => code; |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this); |
| registry.addFieldDeclaration(this, visitor); |
| registry.addConstructorFieldInitializer(this, visitor); |
| } |
| } |
| |
| class HasParameterReferenceVisitor extends RecursiveAstVisitor { |
| Iterable<ParameterElement?> parameters; |
| |
| bool useParameter = false; |
| |
| HasParameterReferenceVisitor(this.parameters); |
| |
| @override |
| void visitSimpleIdentifier(SimpleIdentifier node) { |
| if (parameters.contains(node.staticElement)) { |
| useParameter = true; |
| } else { |
| super.visitSimpleIdentifier(node); |
| } |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| _Visitor(this.rule); |
| |
| @override |
| void visitConstructorFieldInitializer(ConstructorFieldInitializer node) { |
| var declaration = node.parent; |
| if (declaration is ConstructorDeclaration) { |
| if (declaration.constKeyword == null) return; |
| var classDecl = declaration.thisOrAncestorOfType<ClassDeclaration>(); |
| if (classDecl == null) return; |
| // no lint if several constructors |
| var constructorCount = |
| classDecl.members.whereType<ConstructorDeclaration>().length; |
| if (constructorCount > 1) return; |
| |
| var visitor = HasParameterReferenceVisitor( |
| declaration.parameters.parameterElements); |
| node.expression.accept(visitor); |
| if (!visitor.useParameter) { |
| rule.reportLint(node); |
| } |
| } |
| } |
| |
| @override |
| void visitFieldDeclaration(FieldDeclaration node) { |
| if (node.isStatic) return; |
| if (!node.fields.isFinal) return; |
| // only const class |
| var parent = node.parent; |
| if (parent is ClassDeclaration) { |
| var declaredElement = parent.declaredElement; |
| if (declaredElement == null) { |
| return; |
| } |
| if (declaredElement.constructors.every((e) => !e.isConst)) { |
| return; |
| } |
| for (var variable in node.fields.variables) { |
| if (variable.initializer != null) { |
| rule.reportLint(variable); |
| } |
| } |
| } |
| } |
| } |