| // 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/element/element.dart'; |
| import 'package:analyzer/dart/element/nullability_suffix.dart'; |
| import 'package:analyzer/dart/element/type.dart'; |
| import 'package:analyzer/src/dart/element/element.dart'; |
| import 'package:analyzer/src/dart/element/extensions.dart'; |
| import 'package:analyzer/src/dart/element/type.dart'; |
| import 'package:analyzer/src/dart/element/type_algebra.dart'; |
| import 'package:analyzer/src/dart/element/type_schema.dart'; |
| import 'package:analyzer/src/dart/element/type_system.dart'; |
| import 'package:analyzer/src/dart/resolver/variance.dart'; |
| import 'package:analyzer/src/generated/utilities_dart.dart'; |
| import 'package:meta/meta.dart'; |
| |
| /// The instantiation of a [ClassElement] with type arguments. |
| /// |
| /// It is not a [DartType] itself, because it does not have nullability. |
| /// But it should be used where nullability does not make sense - to specify |
| /// superclasses, mixins, and implemented interfaces. |
| class InstantiatedClass { |
| final ClassElement element; |
| final List<DartType> arguments; |
| |
| final Substitution _substitution; |
| |
| InstantiatedClass(this.element, this.arguments) |
| : _substitution = Substitution.fromPairs( |
| element.typeParameters, |
| arguments, |
| ); |
| |
| /// Return the [InstantiatedClass] that corresponds to the [type] - with the |
| /// same element and type arguments, ignoring its nullability suffix. |
| factory InstantiatedClass.of(InterfaceType type) { |
| return InstantiatedClass(type.element, type.typeArguments); |
| } |
| |
| @override |
| int get hashCode { |
| var hash = 0x3fffffff & element.hashCode; |
| for (var i = 0; i < arguments.length; i++) { |
| hash = 0x3fffffff & (hash * 31 + (hash ^ arguments[i].hashCode)); |
| } |
| return hash; |
| } |
| |
| /// Return the interfaces that are directly implemented by this class. |
| List<InstantiatedClass> get interfaces { |
| var interfaces = element.interfaces; |
| |
| var result = List<InstantiatedClass>(interfaces.length); |
| for (var i = 0; i < interfaces.length; i++) { |
| var interface = interfaces[i]; |
| var substituted = _substitution.substituteType(interface); |
| result[i] = InstantiatedClass.of(substituted); |
| } |
| |
| return result; |
| } |
| |
| /// Return `true` if this type represents the type 'Function' defined in the |
| /// dart:core library. |
| bool get isDartCoreFunction { |
| return element.name == 'Function' && element.library.isDartCore; |
| } |
| |
| /// Return the superclass of this type, or `null` if this type represents |
| /// the class 'Object'. |
| InstantiatedClass get superclass { |
| var supertype = element.supertype; |
| if (supertype == null) return null; |
| |
| supertype = _substitution.substituteType(supertype); |
| return InstantiatedClass.of(supertype); |
| } |
| |
| /// Return a list containing all of the superclass constraints defined for |
| /// this class. The list will be empty if this class does not represent a |
| /// mixin declaration. If this class _does_ represent a mixin declaration but |
| /// the declaration does not have an `on` clause, then the list will contain |
| /// the type for the class `Object`. |
| List<InstantiatedClass> get superclassConstraints { |
| var constraints = element.superclassConstraints; |
| |
| var result = List<InstantiatedClass>(constraints.length); |
| for (var i = 0; i < constraints.length; i++) { |
| var constraint = constraints[i]; |
| var substituted = _substitution.substituteType(constraint); |
| result[i] = InstantiatedClass.of(substituted); |
| } |
| |
| return result; |
| } |
| |
| @visibleForTesting |
| InterfaceType get withNullabilitySuffixNone { |
| return withNullability(NullabilitySuffix.none); |
| } |
| |
| @override |
| bool operator ==(Object other) { |
| if (identical(this, other)) return true; |
| |
| if (other is InstantiatedClass) { |
| if (element != other.element) return false; |
| if (arguments.length != other.arguments.length) return false; |
| for (var i = 0; i < arguments.length; i++) { |
| if (arguments[i] != other.arguments[i]) return false; |
| } |
| return true; |
| } |
| return false; |
| } |
| |
| InstantiatedClass mapArguments(DartType Function(DartType) f) { |
| var mappedArguments = arguments.map(f).toList(); |
| return InstantiatedClass(element, mappedArguments); |
| } |
| |
| @override |
| String toString() { |
| var buffer = StringBuffer(); |
| buffer.write(element.name); |
| if (arguments.isNotEmpty) { |
| buffer.write('<'); |
| buffer.write(arguments.join(', ')); |
| buffer.write('>'); |
| } |
| return buffer.toString(); |
| } |
| |
| InterfaceType withNullability(NullabilitySuffix nullability) { |
| return InterfaceTypeImpl( |
| element: element, |
| typeArguments: arguments, |
| nullabilitySuffix: nullability, |
| ); |
| } |
| } |
| |
| class InterfaceLeastUpperBoundHelper { |
| final TypeSystemImpl typeSystem; |
| |
| InterfaceLeastUpperBoundHelper(this.typeSystem); |
| |
| /// This currently does not implement a very complete least upper bound |
| /// algorithm, but handles a couple of the very common cases that are |
| /// causing pain in real code. The current algorithm is: |
| /// 1. If either of the types is a supertype of the other, return it. |
| /// This is in fact the best result in this case. |
| /// 2. If the two types have the same class element and are implicitly or |
| /// explicitly covariant, then take the pointwise least upper bound of |
| /// the type arguments. This is again the best result, except that the |
| /// recursive calls may not return the true least upper bounds. The |
| /// result is guaranteed to be a well-formed type under the assumption |
| /// that the input types were well-formed (and assuming that the |
| /// recursive calls return well-formed types). |
| /// If the variance of the type parameter is contravariant, we take the |
| /// greatest lower bound of the type arguments. If the variance of the |
| /// type parameter is invariant, we verify if the type arguments satisfy |
| /// subtyping in both directions, then choose a bound. |
| /// 3. Otherwise return the spec-defined least upper bound. This will |
| /// be an upper bound, might (or might not) be least, and might |
| /// (or might not) be a well-formed type. |
| /// |
| /// TODO(leafp): Use matchTypes or something similar here to handle the |
| /// case where one of the types is a superclass (but not supertype) of |
| /// the other, e.g. LUB(Iterable<double>, List<int>) = Iterable<num> |
| /// TODO(leafp): Figure out the right final algorithm and implement it. |
| InterfaceTypeImpl compute(InterfaceTypeImpl type1, InterfaceTypeImpl type2) { |
| var nullability = _chooseNullability(type1, type2); |
| |
| // Strip off nullability. |
| type1 = type1.withNullability(NullabilitySuffix.none); |
| type2 = type2.withNullability(NullabilitySuffix.none); |
| |
| if (typeSystem.isSubtypeOf2(type1, type2)) { |
| return type2.withNullability(nullability); |
| } |
| if (typeSystem.isSubtypeOf2(type2, type1)) { |
| return type1.withNullability(nullability); |
| } |
| |
| if (type1.element == type2.element) { |
| var args1 = type1.typeArguments; |
| var args2 = type2.typeArguments; |
| var params = type1.element.typeParameters; |
| assert(args1.length == args2.length); |
| assert(args1.length == params.length); |
| |
| var args = List<DartType>(args1.length); |
| for (int i = 0; i < args1.length; i++) { |
| // TODO (kallentu) : Clean up TypeParameterElementImpl casting once |
| // variance is added to the interface. |
| Variance parameterVariance = |
| (params[i] as TypeParameterElementImpl).variance; |
| if (parameterVariance.isCovariant) { |
| args[i] = typeSystem.getLeastUpperBound(args1[i], args2[i]); |
| } else if (parameterVariance.isContravariant) { |
| if (typeSystem is TypeSystemImpl) { |
| args[i] = typeSystem.getGreatestLowerBound(args1[i], args2[i]); |
| } else { |
| args[i] = typeSystem.getLeastUpperBound(args1[i], args2[i]); |
| } |
| } else if (parameterVariance.isInvariant) { |
| if (!typeSystem.isSubtypeOf2(args1[i], args2[i]) || |
| !typeSystem.isSubtypeOf2(args2[i], args1[i])) { |
| // No bound will be valid, find bound at the interface level. |
| return _computeLeastUpperBound( |
| InstantiatedClass.of(type1), |
| InstantiatedClass.of(type2), |
| ).withNullability(nullability); |
| } |
| // TODO (kallentu) : Fix asymmetric bounds behavior for invariant type |
| // parameters. |
| args[i] = args1[i]; |
| } else { |
| throw StateError('Type parameter ${params[i]} has unknown ' |
| 'variance $parameterVariance for bounds calculation.'); |
| } |
| } |
| |
| return InterfaceTypeImpl( |
| element: type1.element, |
| typeArguments: args, |
| nullabilitySuffix: nullability, |
| ); |
| } |
| |
| var result = _computeLeastUpperBound( |
| InstantiatedClass.of(type1), |
| InstantiatedClass.of(type2), |
| ); |
| return result.withNullability(nullability); |
| } |
| |
| /// Return all of the superinterfaces of the given [type]. |
| @visibleForTesting |
| Set<InstantiatedClass> computeSuperinterfaceSet(InstantiatedClass type) { |
| var result = <InstantiatedClass>{}; |
| _addSuperinterfaces(result, type); |
| if (typeSystem.isNonNullableByDefault) { |
| return result; |
| } else { |
| return result.map((e) { |
| return e.mapArguments(typeSystem.toLegacyType); |
| }).toSet(); |
| } |
| } |
| |
| /// Compute the least upper bound of types [i] and [j], both of which are |
| /// known to be interface types. |
| /// |
| /// In the event that the algorithm fails (which might occur due to a bug in |
| /// the analyzer), `null` is returned. |
| InstantiatedClass _computeLeastUpperBound( |
| InstantiatedClass i, |
| InstantiatedClass j, |
| ) { |
| // compute set of supertypes |
| var si = computeSuperinterfaceSet(i); |
| var sj = computeSuperinterfaceSet(j); |
| |
| // union si with i and sj with j |
| si.add(i); |
| sj.add(j); |
| |
| // compute intersection, reference as set 's' |
| var s = _intersection(si, sj); |
| return _computeTypeAtMaxUniqueDepth(s); |
| } |
| |
| /// Return the length of the longest inheritance path from the [element] to |
| /// Object. |
| @visibleForTesting |
| static int computeLongestInheritancePathToObject(ClassElement element) { |
| return _computeLongestInheritancePathToObject( |
| element, |
| 0, |
| <ClassElement>{}, |
| ); |
| } |
| |
| /// Add all of the superinterfaces of the given [type] to the given [set]. |
| static void _addSuperinterfaces( |
| Set<InstantiatedClass> set, InstantiatedClass type) { |
| for (var interface in type.interfaces) { |
| if (!interface.isDartCoreFunction) { |
| if (set.add(interface)) { |
| _addSuperinterfaces(set, interface); |
| } |
| } |
| } |
| |
| for (var constraint in type.superclassConstraints) { |
| if (!constraint.isDartCoreFunction) { |
| if (set.add(constraint)) { |
| _addSuperinterfaces(set, constraint); |
| } |
| } |
| } |
| |
| var supertype = type.superclass; |
| if (supertype != null && !supertype.isDartCoreFunction) { |
| if (set.add(supertype)) { |
| _addSuperinterfaces(set, supertype); |
| } |
| } |
| } |
| |
| static NullabilitySuffix _chooseNullability( |
| InterfaceTypeImpl type1, |
| InterfaceTypeImpl type2, |
| ) { |
| var nullability1 = type1.nullabilitySuffix; |
| var nullability2 = type2.nullabilitySuffix; |
| if (nullability1 == NullabilitySuffix.question || |
| nullability2 == NullabilitySuffix.question) { |
| return NullabilitySuffix.question; |
| } else if (nullability1 == NullabilitySuffix.star || |
| nullability2 == NullabilitySuffix.star) { |
| return NullabilitySuffix.star; |
| } |
| return NullabilitySuffix.none; |
| } |
| |
| /// Return the length of the longest inheritance path from a subtype of the |
| /// given [element] to Object, where the given [depth] is the length of the |
| /// longest path from the subtype to this type. The set of [visitedElements] |
| /// is used to prevent infinite recursion in the case of a cyclic type |
| /// structure. |
| static int _computeLongestInheritancePathToObject( |
| ClassElement element, int depth, Set<ClassElement> visitedElements) { |
| // Object case |
| if (element.isDartCoreObject || visitedElements.contains(element)) { |
| return depth; |
| } |
| int longestPath = 1; |
| try { |
| visitedElements.add(element); |
| int pathLength; |
| |
| // loop through each of the superinterfaces recursively calling this |
| // method and keeping track of the longest path to return |
| for (InterfaceType interface in element.superclassConstraints) { |
| pathLength = _computeLongestInheritancePathToObject( |
| interface.element, depth + 1, visitedElements); |
| if (pathLength > longestPath) { |
| longestPath = pathLength; |
| } |
| } |
| |
| // loop through each of the superinterfaces recursively calling this |
| // method and keeping track of the longest path to return |
| for (InterfaceType interface in element.interfaces) { |
| pathLength = _computeLongestInheritancePathToObject( |
| interface.element, depth + 1, visitedElements); |
| if (pathLength > longestPath) { |
| longestPath = pathLength; |
| } |
| } |
| |
| // finally, perform this same check on the super type |
| // TODO(brianwilkerson) Does this also need to add in the number of mixin |
| // classes? |
| InterfaceType supertype = element.supertype; |
| if (supertype != null) { |
| pathLength = _computeLongestInheritancePathToObject( |
| supertype.element, depth + 1, visitedElements); |
| if (pathLength > longestPath) { |
| longestPath = pathLength; |
| } |
| } |
| } finally { |
| visitedElements.remove(element); |
| } |
| return longestPath; |
| } |
| |
| /// Return the type from the [types] list that has the longest inheritance |
| /// path to Object of unique length. |
| static InstantiatedClass _computeTypeAtMaxUniqueDepth( |
| List<InstantiatedClass> types, |
| ) { |
| // for each element in Set s, compute the largest inheritance path to Object |
| List<int> depths = List<int>.filled(types.length, 0); |
| int maxDepth = 0; |
| for (int i = 0; i < types.length; i++) { |
| depths[i] = computeLongestInheritancePathToObject(types[i].element); |
| if (depths[i] > maxDepth) { |
| maxDepth = depths[i]; |
| } |
| } |
| // ensure that the currently computed maxDepth is unique, |
| // otherwise, decrement and test for uniqueness again |
| for (; maxDepth >= 0; maxDepth--) { |
| int indexOfLeastUpperBound = -1; |
| int numberOfTypesAtMaxDepth = 0; |
| for (int m = 0; m < depths.length; m++) { |
| if (depths[m] == maxDepth) { |
| numberOfTypesAtMaxDepth++; |
| indexOfLeastUpperBound = m; |
| } |
| } |
| if (numberOfTypesAtMaxDepth == 1) { |
| return types[indexOfLeastUpperBound]; |
| } |
| } |
| // Should be impossible--there should always be exactly one type with the |
| // maximum depth. |
| assert(false); |
| return null; |
| } |
| |
| /// Return the intersection of the [first] and [second] sets of types, where |
| /// intersection is based on the equality of the types themselves. |
| static List<InstantiatedClass> _intersection( |
| Set<InstantiatedClass> first, |
| Set<InstantiatedClass> second, |
| ) { |
| var result = first.toSet(); |
| result.retainAll(second); |
| return result.toList(); |
| } |
| } |
| |
| class LeastUpperBoundHelper { |
| final TypeSystemImpl _typeSystem; |
| |
| LeastUpperBoundHelper(this._typeSystem); |
| |
| InterfaceType get _interfaceTypeFunctionNone { |
| return _typeSystem.typeProvider.functionType.element.instantiate( |
| typeArguments: const [], |
| nullabilitySuffix: NullabilitySuffix.none, |
| ); |
| } |
| |
| /// Compute the least upper bound of two types. |
| /// |
| /// https://github.com/dart-lang/language |
| /// See `resources/type-system/upper-lower-bounds.md` |
| DartType getLeastUpperBound(DartType T1, DartType T2) { |
| // UP(T, T) = T |
| if (identical(T1, T2)) { |
| return T1; |
| } |
| |
| // For any type T, UP(?, T) == T. |
| if (identical(T1, UnknownInferredType.instance)) { |
| return T2; |
| } |
| if (identical(T2, UnknownInferredType.instance)) { |
| return T1; |
| } |
| |
| var T1_isTop = _typeSystem.isTop(T1); |
| var T2_isTop = _typeSystem.isTop(T2); |
| |
| // UP(T1, T2) where TOP(T1) and TOP(T2) |
| if (T1_isTop && T2_isTop) { |
| // * T1 if MORETOP(T1, T2) |
| // * T2 otherwise |
| if (_typeSystem.isMoreTop(T1, T2)) { |
| return T1; |
| } else { |
| return T2; |
| } |
| } |
| |
| // UP(T1, T2) = T1 if TOP(T1) |
| if (T1_isTop) { |
| return T1; |
| } |
| |
| // UP(T1, T2) = T2 if TOP(T2) |
| if (T2_isTop) { |
| return T2; |
| } |
| |
| var T1_isBottom = _typeSystem.isBottom(T1); |
| var T2_isBottom = _typeSystem.isBottom(T2); |
| |
| // UP(T1, T2) where BOTTOM(T1) and BOTTOM(T2) |
| if (T1_isBottom && T2_isBottom) { |
| // * T2 if MOREBOTTOM(T1, T2) |
| // * T1 otherwise |
| if (_typeSystem.isMoreBottom(T1, T2)) { |
| return T2; |
| } else { |
| return T1; |
| } |
| } |
| |
| // UP(T1, T2) = T2 if BOTTOM(T1) |
| if (T1_isBottom) { |
| return T2; |
| } |
| |
| // UP(T1, T2) = T1 if BOTTOM(T2) |
| if (T2_isBottom) { |
| return T1; |
| } |
| |
| var T1_isNull = _typeSystem.isNull(T1); |
| var T2_isNull = _typeSystem.isNull(T2); |
| |
| // UP(T1, T2) where NULL(T1) and NULL(T2) |
| if (T1_isNull && T2_isNull) { |
| // * T2 if MOREBOTTOM(T1, T2) |
| // * T1 otherwise |
| if (_typeSystem.isMoreBottom(T1, T2)) { |
| return T2; |
| } else { |
| return T1; |
| } |
| } |
| |
| var T1_impl = T1 as TypeImpl; |
| var T2_impl = T2 as TypeImpl; |
| |
| var T1_nullability = T1_impl.nullabilitySuffix; |
| var T2_nullability = T2_impl.nullabilitySuffix; |
| |
| // UP(T1, T2) where NULL(T1) |
| if (T1_isNull) { |
| // * T2 if T2 is nullable |
| // * T2* if Null <: T2 or T1 <: Object (that is, T1 or T2 is legacy) |
| // * T2? otherwise |
| if (_typeSystem.isNullable(T2)) { |
| return T2; |
| } else if (T1_nullability == NullabilitySuffix.star || |
| T2_nullability == NullabilitySuffix.star) { |
| return T2_impl.withNullability(NullabilitySuffix.star); |
| } else { |
| return _typeSystem.makeNullable(T2); |
| } |
| } |
| |
| // UP(T1, T2) where NULL(T2) |
| if (T2_isNull) { |
| // * T1 if T1 is nullable |
| // * T1* if Null <: T1 or T2 <: Object (that is, T1 or T2 is legacy) |
| // * T1? otherwise |
| if (_typeSystem.isNullable(T1)) { |
| return T1; |
| } else if (T1_nullability == NullabilitySuffix.star || |
| T2_nullability == NullabilitySuffix.star) { |
| return T1_impl.withNullability(NullabilitySuffix.star); |
| } else { |
| return _typeSystem.makeNullable(T1); |
| } |
| } |
| |
| var T1_isObject = _typeSystem.isObject(T1); |
| var T2_isObject = _typeSystem.isObject(T2); |
| |
| // UP(T1, T2) where OBJECT(T1) and OBJECT(T2) |
| if (T1_isObject && T2_isObject) { |
| // * T1 if MORETOP(T1, T2) |
| // * T2 otherwise |
| if (_typeSystem.isMoreTop(T1, T2)) { |
| return T1; |
| } else { |
| return T2; |
| } |
| } |
| |
| // UP(T1, T2) where OBJECT(T1) |
| if (T1_isObject) { |
| // * T1 if T2 is non-nullable |
| // * T1? otherwise |
| if (_typeSystem.isNonNullable(T2)) { |
| return T1; |
| } else { |
| return _typeSystem.makeNullable(T1); |
| } |
| } |
| |
| // UP(T1, T2) where OBJECT(T2) |
| if (T2_isObject) { |
| // * T2 if T1 is non-nullable |
| // * T2? otherwise |
| if (_typeSystem.isNonNullable(T1)) { |
| return T2; |
| } else { |
| return _typeSystem.makeNullable(T2); |
| } |
| } |
| |
| // UP(T1*, T2*) = S* where S is UP(T1, T2) |
| // UP(T1*, T2?) = S? where S is UP(T1, T2) |
| // UP(T1?, T2*) = S? where S is UP(T1, T2) |
| // UP(T1*, T2) = S* where S is UP(T1, T2) |
| // UP(T1, T2*) = S* where S is UP(T1, T2) |
| // UP(T1?, T2?) = S? where S is UP(T1, T2) |
| // UP(T1?, T2) = S? where S is UP(T1, T2) |
| // UP(T1, T2?) = S? where S is UP(T1, T2) |
| if (T1_nullability != NullabilitySuffix.none || |
| T2_nullability != NullabilitySuffix.none) { |
| var resultNullability = NullabilitySuffix.none; |
| if (T1_nullability == NullabilitySuffix.question || |
| T2_nullability == NullabilitySuffix.question) { |
| resultNullability = NullabilitySuffix.question; |
| } else if (T1_nullability == NullabilitySuffix.star || |
| T2_nullability == NullabilitySuffix.star) { |
| resultNullability = NullabilitySuffix.star; |
| } |
| var T1_none = T1_impl.withNullability(NullabilitySuffix.none); |
| var T2_none = T2_impl.withNullability(NullabilitySuffix.none); |
| var S = getLeastUpperBound(T1_none, T2_none); |
| return (S as TypeImpl).withNullability(resultNullability); |
| } |
| |
| assert(T1_nullability == NullabilitySuffix.none); |
| assert(T2_nullability == NullabilitySuffix.none); |
| |
| // UP(X1 extends B1, T2) |
| // UP(X1 & B1, T2) |
| if (T1 is TypeParameterType) { |
| // T2 if X1 <: T2 |
| if (_typeSystem.isSubtypeOf2(T1, T2)) { |
| return T2; |
| } |
| // otherwise X1 if T2 <: X1 |
| if (_typeSystem.isSubtypeOf2(T2, T1)) { |
| return T1; |
| } |
| // otherwise UP(B1[Object/X1], T2) |
| var T1_toObject = _typeParameterResolveToObjectBounds(T1); |
| return getLeastUpperBound(T1_toObject, T2); |
| } |
| |
| // UP(T1, X2 extends B2) |
| // UP(T1, X2 & B2) |
| if (T2 is TypeParameterType) { |
| // X2 if T1 <: X2 |
| if (_typeSystem.isSubtypeOf2(T1, T2)) { |
| // TODO(scheglov) How to get here? |
| return T2; |
| } |
| // otherwise T1 if X2 <: T1 |
| if (_typeSystem.isSubtypeOf2(T2, T1)) { |
| return T1; |
| } |
| // otherwise UP(T1, B2[Object/X2]) |
| var T2_toObject = _typeParameterResolveToObjectBounds(T2); |
| return getLeastUpperBound(T1, T2_toObject); |
| } |
| |
| // UP(T Function<...>(...), Function) = Function |
| if (T1 is FunctionType && T2.isDartCoreFunction) { |
| return T2; |
| } |
| |
| // UP(Function, T Function<...>(...)) = Function |
| if (T1.isDartCoreFunction && T2 is FunctionType) { |
| return T1; |
| } |
| |
| // UP(T Function<...>(...), S Function<...>(...)) = Function |
| // And other, more interesting variants. |
| if (T1 is FunctionType && T2 is FunctionType) { |
| return _functionType(T1, T2); |
| } |
| |
| // UP(T Function<...>(...), T2) = UP(Object, T2) |
| if (T1 is FunctionType) { |
| return getLeastUpperBound(_typeSystem.objectNone, T2); |
| } |
| |
| // UP(T1, T Function<...>(...)) = UP(T1, Object) |
| if (T2 is FunctionType) { |
| return getLeastUpperBound(T1, _typeSystem.objectNone); |
| } |
| |
| // UP(T1, T2) = T2 if T1 <: T2 |
| // UP(T1, T2) = T1 if T2 <: T1 |
| // And other, more complex variants of interface types. |
| var helper = InterfaceLeastUpperBoundHelper(_typeSystem); |
| return helper.compute(T1, T2); |
| } |
| |
| /// Compute the least upper bound of function types [f] and [g]. |
| /// |
| /// https://github.com/dart-lang/language |
| /// See `resources/type-system/upper-lower-bounds.md` |
| DartType _functionType(FunctionType f, FunctionType g) { |
| var fTypeFormals = f.typeFormals; |
| var gTypeFormals = g.typeFormals; |
| |
| // The number of type parameters must be the same. |
| // Otherwise the result is `Function`. |
| if (fTypeFormals.length != gTypeFormals.length) { |
| return _interfaceTypeFunctionNone; |
| } |
| |
| // The bounds of type parameters must be equal. |
| // Otherwise the result is `Function`. |
| var freshTypeFormalTypes = |
| FunctionTypeImpl.relateTypeFormals(f, g, (t, s, _, __) => t == s); |
| if (freshTypeFormalTypes == null) { |
| return _interfaceTypeFunctionNone; |
| } |
| |
| var typeFormals = freshTypeFormalTypes |
| .map<TypeParameterElement>((t) => t.element) |
| .toList(); |
| |
| f = f.instantiate(freshTypeFormalTypes); |
| g = g.instantiate(freshTypeFormalTypes); |
| |
| var fParameters = f.parameters; |
| var gParameters = g.parameters; |
| |
| var parameters = <ParameterElement>[]; |
| var fIndex = 0; |
| var gIndex = 0; |
| while (fIndex < fParameters.length && gIndex < gParameters.length) { |
| var fParameter = fParameters[fIndex]; |
| var gParameter = gParameters[gIndex]; |
| if (fParameter.isRequiredPositional) { |
| if (gParameter.isRequiredPositional) { |
| fIndex++; |
| gIndex++; |
| parameters.add( |
| fParameter.copyWith( |
| type: _parameterType(fParameter, gParameter), |
| ), |
| ); |
| } else { |
| break; |
| } |
| } else if (fParameter.isOptionalPositional) { |
| if (gParameter.isOptionalPositional) { |
| fIndex++; |
| gIndex++; |
| parameters.add( |
| fParameter.copyWith( |
| type: _parameterType(fParameter, gParameter), |
| ), |
| ); |
| } else { |
| break; |
| } |
| } else if (fParameter.isNamed) { |
| if (gParameter.isNamed) { |
| var compareNames = fParameter.name.compareTo(gParameter.name); |
| if (compareNames == 0) { |
| fIndex++; |
| gIndex++; |
| parameters.add( |
| fParameter.copyWith( |
| type: _parameterType(fParameter, gParameter), |
| kind: fParameter.isRequiredNamed || gParameter.isRequiredNamed |
| ? ParameterKind.NAMED_REQUIRED |
| : ParameterKind.NAMED, |
| ), |
| ); |
| } else if (compareNames < 0) { |
| if (fParameter.isRequiredNamed) { |
| // We cannot skip required named. |
| return _interfaceTypeFunctionNone; |
| } else { |
| fIndex++; |
| } |
| } else { |
| assert(compareNames > 0); |
| if (gParameter.isRequiredNamed) { |
| // We cannot skip required named. |
| return _interfaceTypeFunctionNone; |
| } else { |
| gIndex++; |
| } |
| } |
| } else { |
| break; |
| } |
| } |
| } |
| |
| while (fIndex < fParameters.length) { |
| var fParameter = fParameters[fIndex++]; |
| if (fParameter.isNotOptional) { |
| return _interfaceTypeFunctionNone; |
| } |
| } |
| |
| while (gIndex < gParameters.length) { |
| var gParameter = gParameters[gIndex++]; |
| if (gParameter.isNotOptional) { |
| return _interfaceTypeFunctionNone; |
| } |
| } |
| |
| var returnType = getLeastUpperBound(f.returnType, g.returnType); |
| |
| return FunctionTypeImpl( |
| typeFormals: typeFormals, |
| parameters: parameters, |
| returnType: returnType, |
| nullabilitySuffix: NullabilitySuffix.none, |
| ); |
| } |
| |
| DartType _parameterType(ParameterElement a, ParameterElement b) { |
| return _typeSystem.getGreatestLowerBound(a.type, b.type); |
| } |
| |
| /// TODO(scheglov) Use greatest closure. |
| /// See https://github.com/dart-lang/language/pull/1195 |
| DartType _typeParameterResolveToObjectBounds(DartType type) { |
| var element = type.element; |
| |
| var objectType = _typeSystem.isNonNullableByDefault |
| ? _typeSystem.objectQuestion |
| : _typeSystem.objectStar; |
| |
| type = type.resolveToBound(objectType); |
| return Substitution.fromMap({element: objectType}).substituteType(type); |
| } |
| } |
