1 /* 2 * Copyright (C) 2021 The Guava 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 17 package com.google.common.math; 18 19 import static java.lang.annotation.ElementType.FIELD; 20 import static java.lang.annotation.ElementType.METHOD; 21 import static java.lang.annotation.ElementType.PARAMETER; 22 import static java.lang.annotation.RetentionPolicy.RUNTIME; 23 24 import com.google.common.annotations.GwtCompatible; 25 import java.lang.annotation.Retention; 26 import java.lang.annotation.Target; 27 28 /** 29 * Marks a "top-level" type-variable usage as the closest we can get to "non-nullable when 30 * non-nullable; nullable when nullable" (like the Android <a 31 * href="https://android.googlesource.com/platform/libcore/+/master/luni/src/main/java/libcore/util/NullFromTypeParam.java">{@code 32 * NullFromTypeParam}</a>). 33 * 34 * <p>Consumers of this annotation include: 35 * 36 * <ul> 37 * <li>Kotlin, for which it makes the type-variable usage (a) a Kotlin platform type when the type 38 * argument is non-nullable and (b) nullable when the type argument is nullable. We use this 39 * to "undo" {@link ElementTypesAreNonnullByDefault}. 40 * <li><a href="https://developers.google.com/j2objc">J2ObjC</a> 41 * <li>{@code NullPointerTester}, at least in the Android backport (where the type-use annotations 42 * {@code NullPointerTester} would need are not available) and in case of <a 43 * href="https://bugs.openjdk.java.net/browse/JDK-8202469">JDK-8202469</a> 44 * </ul> 45 * 46 */ 47 @GwtCompatible 48 @Retention(RUNTIME) 49 @Target({FIELD, METHOD, PARAMETER}) 50 @javax.annotation.meta.TypeQualifierNickname 51 @javax.annotation.Nonnull(when = javax.annotation.meta.When.UNKNOWN) 52 @interface ParametricNullness {} 53