| // 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/analysis/features.dart'; |
| import 'package:analyzer/dart/ast/ast.dart'; |
| import 'package:analyzer/dart/ast/visitor.dart'; |
| |
| import '../analyzer.dart'; |
| |
| const _desc = r"Don't cast a nullable value to a non nullable type."; |
| |
| const _details = r''' |
| |
| Don't cast a nullable value to a non nullable type. This hides a null check |
| and most of the time it is not what is expected. |
| |
| **BAD:** |
| ``` |
| class A {} |
| class B extends A {} |
| |
| A? a; |
| var v = a as B; |
| var v = a as A; |
| ``` |
| |
| **GOOD:** |
| ``` |
| class A {} |
| class B extends A {} |
| |
| A? a; |
| var v = a! as B; |
| var v = a!; |
| ``` |
| |
| '''; |
| |
| class CastNullableToNonNullable extends LintRule implements NodeLintRule { |
| CastNullableToNonNullable() |
| : super( |
| name: 'cast_nullable_to_non_nullable', |
| description: _desc, |
| details: _details, |
| maturity: Maturity.experimental, |
| group: Group.style, |
| ); |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| if (!context.isEnabled(Feature.non_nullable)) { |
| return; |
| } |
| |
| final visitor = _Visitor(this, context); |
| registry.addAsExpression(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| _Visitor(this.rule, this.context); |
| |
| final LintRule rule; |
| final LinterContext context; |
| |
| @override |
| void visitAsExpression(AsExpression node) { |
| final expressionType = node.expression.staticType; |
| final type = node.type.type; |
| if (!expressionType.isDynamic && |
| context.typeSystem.isNullable(expressionType) && |
| context.typeSystem.isNonNullable(type)) { |
| rule.reportLint(node); |
| } |
| } |
| } |