| // Copyright (c) 2019, 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:_fe_analyzer_shared/src/flow_analysis/flow_analysis.dart'; |
| import 'package:analyzer/dart/element/element.dart'; |
| import 'package:analyzer/dart/element/type_system.dart'; |
| import 'package:nnbd_migration/src/decorated_type.dart'; |
| import 'package:nnbd_migration/src/nullability_node.dart'; |
| import 'package:nnbd_migration/src/variables.dart'; |
| |
| /// [TypeOperations] that works with [DecoratedType]s. |
| class DecoratedTypeOperations |
| implements TypeOperations<PromotableElement, DecoratedType> { |
| final TypeSystem _typeSystem; |
| final Variables _variableRepository; |
| final NullabilityGraph _graph; |
| |
| DecoratedTypeOperations( |
| this._typeSystem, this._variableRepository, this._graph); |
| |
| @override |
| bool isSameType(DecoratedType type1, DecoratedType type2) { |
| return type1 == type2; |
| } |
| |
| @override |
| bool isSubtypeOf(DecoratedType leftType, DecoratedType rightType) { |
| if (!_typeSystem.isSubtypeOf(leftType.type, rightType.type)) { |
| // Pre-migrated types don't meet the subtype requirement. Not a subtype. |
| return false; |
| } else if (rightType.node == _graph.never && |
| leftType.node != _graph.never) { |
| // The "never" node will never be nullable, so not a subtype. |
| return false; |
| } else { |
| // We don't know whether a subtype relation will hold once the graph is |
| // solved. Assume it will. |
| return true; |
| } |
| } |
| |
| @override |
| DecoratedType promoteToNonNull(DecoratedType type) { |
| return type.withNode(_graph.never); |
| } |
| |
| @override |
| DecoratedType tryPromoteToType(DecoratedType to, DecoratedType from) { |
| // TODO(paulberry): implement appropriate logic for type variable promotion. |
| if (isSubtypeOf(to, from)) { |
| return to; |
| } |
| |
| // Allow promotion from non-null types to other types, preserving non-null. |
| var keepNonNull = promoteToNonNull(to); |
| if (isSubtypeOf(keepNonNull, from)) { |
| return keepNonNull; |
| } else { |
| return null; |
| } |
| } |
| |
| @override |
| DecoratedType variableType(PromotableElement variable) { |
| return _variableRepository.decoratedElementType(variable); |
| } |
| } |