| // 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 'package:analyzer/dart/element/type.dart'; |
| |
| import '../analyzer.dart'; |
| |
| const _desc = r"Don't assign to `void`."; |
| |
| const _details = r''' |
| **DON'T** assign to `void`. |
| |
| **BAD:** |
| ```dart |
| class A<T> { |
| T value; |
| void test(T arg) { } |
| } |
| |
| void main() { |
| A<void> a = A<void>(); |
| a.value = 1; // LINT |
| a.test(1); // LINT |
| } |
| ``` |
| '''; |
| |
| class VoidChecks extends LintRule { |
| static const LintCode code = LintCode( |
| 'void_checks', "Assignment to a variable of type 'void'.", |
| correctionMessage: |
| 'Try removing the assignment or changing the type of the variable.'); |
| |
| VoidChecks() |
| : super( |
| name: 'void_checks', |
| description: _desc, |
| details: _details, |
| group: Group.style); |
| |
| @override |
| LintCode get lintCode => code; |
| |
| @override |
| void registerNodeProcessors( |
| NodeLintRegistry registry, LinterContext context) { |
| var visitor = _Visitor(this, context); |
| registry.addAssignedVariablePattern(this, visitor); |
| registry.addAssignmentExpression(this, visitor); |
| registry.addInstanceCreationExpression(this, visitor); |
| registry.addMethodInvocation(this, visitor); |
| registry.addReturnStatement(this, visitor); |
| } |
| } |
| |
| class _Visitor extends SimpleAstVisitor<void> { |
| final LintRule rule; |
| |
| final TypeSystem typeSystem; |
| |
| _Visitor(this.rule, LinterContext context) : typeSystem = context.typeSystem; |
| |
| bool isTypeAcceptableWhenExpectingFutureOrVoid(DartType type) { |
| if (type is DynamicType) return true; |
| if (isTypeAcceptableWhenExpectingVoid(type)) return true; |
| if (type.isDartAsyncFutureOr || |
| type.isDartAsyncFuture && |
| type is InterfaceType && |
| isTypeAcceptableWhenExpectingFutureOrVoid( |
| type.typeArguments.first)) { |
| return true; |
| } |
| |
| return false; |
| } |
| |
| bool isTypeAcceptableWhenExpectingVoid(DartType type) { |
| if (type is VoidType) return true; |
| if (type.isDartCoreNull) return true; |
| if (type is NeverType) return true; |
| if (type.isDartAsyncFuture && |
| type is InterfaceType && |
| isTypeAcceptableWhenExpectingVoid(type.typeArguments.first)) { |
| return true; |
| } |
| return false; |
| } |
| |
| @override |
| void visitAssignedVariablePattern(AssignedVariablePattern node) { |
| var valueType = node.matchedValueType; |
| var element = node.element; |
| if (element is! VariableElement) return; |
| _check(element.type, valueType, node); |
| } |
| |
| @override |
| void visitAssignmentExpression(AssignmentExpression node) { |
| var type = node.writeType; |
| _check(type, node.rightHandSide.staticType, node, |
| checkedNode: node.rightHandSide); |
| } |
| |
| @override |
| void visitInstanceCreationExpression(InstanceCreationExpression node) { |
| var args = node.argumentList.arguments; |
| var parameters = node.constructorName.staticElement?.parameters; |
| if (parameters != null) { |
| _checkArgs(args, parameters); |
| } |
| } |
| |
| @override |
| void visitMethodInvocation(MethodInvocation node) { |
| var type = node.staticInvokeType; |
| if (type is FunctionType) { |
| var args = node.argumentList.arguments; |
| var parameters = type.parameters; |
| _checkArgs(args, parameters); |
| } |
| } |
| |
| @override |
| void visitReturnStatement(ReturnStatement node) { |
| var parent = node.thisOrAncestorMatching((e) => |
| e is FunctionExpression || |
| e is MethodDeclaration || |
| e is FunctionDeclaration); |
| if (parent is FunctionExpression) { |
| var type = parent.staticType; |
| if (type is FunctionType) { |
| _check(type.returnType, node.expression?.staticType, node, |
| checkedNode: node.expression); |
| } |
| } else if (parent is MethodDeclaration) { |
| _check( |
| parent.declaredElement?.returnType, node.expression?.staticType, node, |
| checkedNode: node.expression); |
| } else if (parent is FunctionDeclaration) { |
| _check( |
| parent.declaredElement?.returnType, node.expression?.staticType, node, |
| checkedNode: node.expression); |
| } |
| } |
| |
| void _check(DartType? expectedType, DartType? type, AstNode node, |
| {AstNode? checkedNode}) { |
| checkedNode ??= node; |
| if (expectedType == null || type == null) { |
| return; |
| } |
| if (expectedType is VoidType && |
| type is! DynamicType && |
| node is ReturnStatement) { |
| return; |
| } |
| if (expectedType is VoidType && !isTypeAcceptableWhenExpectingVoid(type)) { |
| rule.reportLint(node); |
| } else if (expectedType.isDartAsyncFutureOr && |
| (expectedType as InterfaceType).typeArguments.first is VoidType && |
| !isTypeAcceptableWhenExpectingFutureOrVoid(type)) { |
| rule.reportLint(node); |
| } else if (checkedNode is FunctionExpression && |
| checkedNode.body is! ExpressionFunctionBody && |
| expectedType is FunctionType && |
| type is FunctionType) { |
| _check(expectedType.returnType, type.returnType, node, |
| checkedNode: checkedNode); |
| } |
| } |
| |
| void _checkArgs( |
| NodeList<Expression> args, List<ParameterElement> parameters) { |
| for (var arg in args) { |
| var parameterElement = arg.staticParameterElement; |
| if (parameterElement != null) { |
| var type = parameterElement.type; |
| var expression = arg is NamedExpression ? arg.expression : arg; |
| _check(type, expression.staticType, expression); |
| } |
| } |
| } |
| } |