com.google.common.io.ParametricNullness Maven / Gradle / Ivy
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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including
all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and
JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up
with different versions on classes on the class path).
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/*
* Copyright (C) 2021 The Guava Authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.common.io;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.ElementType.PARAMETER;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
/**
* Annotates a "top-level" type-variable usage that takes its nullness from the type argument
* supplied by the user of the class. For example, {@code Multiset.Entry.getElement()} returns
* {@code @ParametricNullness E}, which means:
*
*
* - {@code getElement} on a {@code Multiset.Entry<@NonNull String>} returns {@code @NonNull
* String}.
*
- {@code getElement} on a {@code Multiset.Entry<@Nullable String>} returns {@code @Nullable
* String}.
*
*
* This is the same behavior as type-variable usages have to Kotlin and to the Checker Framework.
* Contrast the method above to:
*
*
* - methods whose return type is a type variable but which can never return {@code null},
* typically because the type forbids nullable type arguments: For example, {@code
* ImmutableList.get} returns {@code E}, but that value is never {@code null}. (Accordingly,
* {@code ImmutableList} is declared to forbid {@code ImmutableList<@Nullable String>}.)
*
- methods whose return type is a type variable but which can return {@code null} regardless
* of the type argument supplied by the user of the class: For example, {@code
* ImmutableMap.get} returns {@code @Nullable E} because the method can return {@code null}
* even on an {@code ImmutableMap
}.
*
*
* Consumers of this annotation include:
*
*
* - Kotlin, for which it makes the type-variable usage (a) a Kotlin platform type when the type
* argument is non-nullable and (b) nullable when the type argument is nullable. We use this
* to "undo" {@link ElementTypesAreNonnullByDefault}. It is the best we can do for Kotlin
* under our current constraints.
*
- NullAway, which will treat it
* identically to {@code Nullable} as of version 0.9.9. To treat it that way before then,
* you can set {@code
* -XepOpt:NullAway:CustomNullableAnnotations=com.google.common.base.ParametricNullness,...,com.google.common.util.concurrent.ParametricNullness},
* where the {@code ...} contains the names of all the other {@code ParametricNullness}
* annotations in Guava. Or you might prefer to omit Guava from your {@code AnnotatedPackages}
* list.
*
- J2ObjC
*
- {@code NullPointerTester}, at least in the Android backport (where the type-use annotations
* {@code NullPointerTester} would need are not available) and in case of JDK-8202469
*
*
* This annotation is a temporary hack. We will remove it after we're able to adopt the JSpecify nullness annotations and tools no longer need
* it.
*/
@GwtCompatible
@Retention(RUNTIME)
@Target({FIELD, METHOD, PARAMETER})
@javax.annotation.meta.TypeQualifierNickname
@javax.annotation.Nonnull(when = javax.annotation.meta.When.UNKNOWN)
@interface ParametricNullness {}