1 /* 2 * Copyright 2020 The JSpecify Authors. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 import org.jspecify.annotations.NullMarked; 17 import org.jspecify.annotations.Nullable; 18 19 @NullMarked 20 interface CovariantReturns { makeObject()21 @Nullable Object makeObject(); 22 makeImplicitlyObjectBounded()23 Lib<?> makeImplicitlyObjectBounded(); 24 makeExplicitlyObjectBounded()25 Lib<? extends @Nullable Object> makeExplicitlyObjectBounded(); 26 27 interface Subtype extends CovariantReturns { 28 @Override makeObject()29 Object makeObject(); 30 31 @Override makeImplicitlyObjectBounded()32 Lib<? extends Object> makeImplicitlyObjectBounded(); 33 34 @Override makeExplicitlyObjectBounded()35 Lib<? extends Object> makeExplicitlyObjectBounded(); 36 } 37 go(Subtype s)38 default void go(Subtype s) { 39 checkObject(s.makeObject()); 40 checkLibOfObject(s.makeImplicitlyObjectBounded()); 41 checkLibOfObject(s.makeExplicitlyObjectBounded()); 42 } 43 checkObject(Object o)44 void checkObject(Object o); 45 checkLibOfObject(Lib<? extends Object> o)46 void checkLibOfObject(Lib<? extends Object> o); 47 48 interface Lib<T extends @Nullable Object> {} 49 } 50