001 /*
002 * Copyright 2010-2015 JetBrains s.r.o.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017 package org.jetbrains.kotlin.types;
018
019 import kotlin.Unit;
020 import kotlin.jvm.functions.Function1;
021 import org.jetbrains.annotations.NotNull;
022 import org.jetbrains.annotations.Nullable;
023 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
024 import org.jetbrains.kotlin.descriptors.ClassifierDescriptor;
025 import org.jetbrains.kotlin.descriptors.TypeParameterDescriptor;
026 import org.jetbrains.kotlin.descriptors.annotations.Annotations;
027 import org.jetbrains.kotlin.resolve.calls.inference.CallHandle;
028 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystem;
029 import org.jetbrains.kotlin.resolve.calls.inference.ConstraintSystemBuilderImpl;
030 import org.jetbrains.kotlin.resolve.scopes.TypeIntersectionScope;
031 import org.jetbrains.kotlin.types.checker.KotlinTypeChecker;
032
033 import java.util.*;
034
035 import static org.jetbrains.kotlin.resolve.calls.inference.constraintPosition.ConstraintPositionKind.SPECIAL;
036 import static org.jetbrains.kotlin.resolve.descriptorUtil.DescriptorUtilsKt.getBuiltIns;
037
038 public class TypeIntersector {
039
040 public static boolean isIntersectionEmpty(@NotNull KotlinType typeA, @NotNull KotlinType typeB) {
041 return intersectTypes(KotlinTypeChecker.DEFAULT, new LinkedHashSet<KotlinType>(Arrays.asList(typeA, typeB))) == null;
042 }
043
044 @Nullable
045 public static KotlinType intersectTypes(@NotNull KotlinTypeChecker typeChecker, @NotNull Collection<KotlinType> types) {
046 assert !types.isEmpty() : "Attempting to intersect empty collection of types, this case should be dealt with on the call site.";
047
048 if (types.size() == 1) {
049 return types.iterator().next();
050 }
051
052 // Intersection of T1..Tn is an intersection of their non-null versions,
053 // made nullable is they all were nullable
054 KotlinType nothingOrNullableNothing = null;
055 boolean allNullable = true;
056 List<KotlinType> nullabilityStripped = new ArrayList<KotlinType>(types.size());
057 for (KotlinType type : types) {
058 if (type.isError()) continue;
059
060 if (KotlinBuiltIns.isNothingOrNullableNothing(type)) {
061 nothingOrNullableNothing = type;
062 }
063 allNullable &= type.isMarkedNullable();
064 nullabilityStripped.add(TypeUtils.makeNotNullable(type));
065 }
066
067 if (nothingOrNullableNothing != null) {
068 return TypeUtils.makeNullableAsSpecified(nothingOrNullableNothing, allNullable);
069 }
070
071 if (nullabilityStripped.isEmpty()) {
072 // All types were errors
073 return ErrorUtils.createErrorType("Intersection of error types: " + types);
074 }
075
076 // Now we remove types that have subtypes in the list
077 List<KotlinType> resultingTypes = new ArrayList<KotlinType>();
078 outer:
079 for (KotlinType type : nullabilityStripped) {
080 if (!TypeUtils.canHaveSubtypes(typeChecker, type)) {
081 for (KotlinType other : nullabilityStripped) {
082 // It makes sense to check for subtyping (other <: type), despite that
083 // type is not supposed to be open, for there're enums
084 if (!TypeUnifier.mayBeEqual(type, other) && !typeChecker.isSubtypeOf(type, other) && !typeChecker.isSubtypeOf(other, type)) {
085 return null;
086 }
087 }
088 return TypeUtils.makeNullableAsSpecified(type, allNullable);
089 }
090 else {
091 for (KotlinType other : nullabilityStripped) {
092 if (!type.equals(other) && typeChecker.isSubtypeOf(other, type)) {
093 continue outer;
094 }
095 }
096 }
097
098 // Don't add type if it is already present, to avoid trivial type intersections in result
099 for (KotlinType other : resultingTypes) {
100 if (typeChecker.equalTypes(other, type)) {
101 continue outer;
102 }
103 }
104 resultingTypes.add(type);
105 }
106
107 if (resultingTypes.isEmpty()) {
108 // If we ended up here, it means that all types from `nullabilityStripped` were excluded by the code above
109 // most likely, this is because they are all semantically interchangeable (e.g. List<Foo>! and List<Foo>),
110 // in that case, we can safely select the best representative out of that set and return it
111 // TODO: maybe return the most specific among the types that are subtypes to all others in the `nullabilityStripped`?
112 // TODO: e.g. among {Int, Int?, Int!}, return `Int` (now it returns `Int!`).
113 KotlinType bestRepresentative = FlexibleTypesKt.singleBestRepresentative(nullabilityStripped);
114 if (bestRepresentative == null) {
115 throw new AssertionError("Empty intersection for types " + types);
116 }
117 return TypeUtils.makeNullableAsSpecified(bestRepresentative, allNullable);
118 }
119
120 if (resultingTypes.size() == 1) {
121 return TypeUtils.makeNullableAsSpecified(resultingTypes.get(0), allNullable);
122 }
123
124 TypeConstructor constructor = new IntersectionTypeConstructor(Annotations.Companion.getEMPTY(), resultingTypes);
125
126 return KotlinTypeImpl.create(
127 Annotations.Companion.getEMPTY(),
128 constructor,
129 allNullable,
130 Collections.<TypeProjection>emptyList(),
131 TypeIntersectionScope.create("member scope for intersection type " + constructor, resultingTypes)
132 );
133 }
134
135 /**
136 * Note: this method was used in overload and override bindings to approximate type parameters with several bounds,
137 * but as it turned out at some point, that logic was inconsistent with Java rules, so it was simplified.
138 * Most of the other usages of this method are left untouched but probably should be investigated closely if they're still valid.
139 */
140 @NotNull
141 public static KotlinType getUpperBoundsAsType(@NotNull TypeParameterDescriptor descriptor) {
142 List<KotlinType> upperBounds = descriptor.getUpperBounds();
143 assert !upperBounds.isEmpty() : "Upper bound list is empty: " + descriptor;
144 KotlinType upperBoundsAsType = intersectTypes(KotlinTypeChecker.DEFAULT, upperBounds);
145 return upperBoundsAsType != null ? upperBoundsAsType : getBuiltIns(descriptor).getNothingType();
146 }
147
148 private static class TypeUnifier {
149 private static class TypeParameterUsage {
150 private final TypeParameterDescriptor typeParameterDescriptor;
151 private final Variance howTheTypeParameterIsUsed;
152
153 public TypeParameterUsage(TypeParameterDescriptor typeParameterDescriptor, Variance howTheTypeParameterIsUsed) {
154 this.typeParameterDescriptor = typeParameterDescriptor;
155 this.howTheTypeParameterIsUsed = howTheTypeParameterIsUsed;
156 }
157 }
158
159 public static boolean mayBeEqual(@NotNull KotlinType type, @NotNull KotlinType other) {
160 return unify(type, other);
161 }
162
163 private static boolean unify(KotlinType withParameters, KotlinType expected) {
164 // T -> how T is used
165 final Map<TypeParameterDescriptor, Variance> parameters = new HashMap<TypeParameterDescriptor, Variance>();
166 Function1<TypeParameterUsage, Unit> processor = new Function1<TypeParameterUsage, Unit>() {
167 @Override
168 public Unit invoke(TypeParameterUsage parameterUsage) {
169 Variance howTheTypeIsUsedBefore = parameters.get(parameterUsage.typeParameterDescriptor);
170 if (howTheTypeIsUsedBefore == null) {
171 howTheTypeIsUsedBefore = Variance.INVARIANT;
172 }
173 parameters.put(parameterUsage.typeParameterDescriptor,
174 parameterUsage.howTheTypeParameterIsUsed.superpose(howTheTypeIsUsedBefore));
175 return Unit.INSTANCE;
176 }
177 };
178 processAllTypeParameters(withParameters, Variance.INVARIANT, processor);
179 processAllTypeParameters(expected, Variance.INVARIANT, processor);
180 ConstraintSystem.Builder constraintSystem = new ConstraintSystemBuilderImpl();
181 TypeSubstitutor substitutor = constraintSystem.registerTypeVariables(CallHandle.NONE.INSTANCE, parameters.keySet(), false);
182 constraintSystem.addSubtypeConstraint(withParameters, substitutor.substitute(expected, Variance.INVARIANT), SPECIAL.position());
183
184 return constraintSystem.build().getStatus().isSuccessful();
185 }
186
187 private static void processAllTypeParameters(KotlinType type, Variance howThisTypeIsUsed, Function1<TypeParameterUsage, Unit> result) {
188 ClassifierDescriptor descriptor = type.getConstructor().getDeclarationDescriptor();
189 if (descriptor instanceof TypeParameterDescriptor) {
190 result.invoke(new TypeParameterUsage((TypeParameterDescriptor) descriptor, howThisTypeIsUsed));
191 }
192 for (TypeProjection projection : type.getArguments()) {
193 if (projection.isStarProjection()) continue;
194 processAllTypeParameters(projection.getType(), projection.getProjectionKind(), result);
195 }
196 }
197 }
198 }