001/* 002 * Copyright 2016 The Error Prone Authors. 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 017package com.google.errorprone.annotations; 018 019import java.lang.annotation.Documented; 020import java.lang.annotation.ElementType; 021import java.lang.annotation.Retention; 022import java.lang.annotation.RetentionPolicy; 023import java.lang.annotation.Target; 024import java.util.Collection; 025 026/** 027 * Declares that a parameter to a method must be "compatible with" one of the type parameters in the 028 * method's enclosing class, or on the method itself. "Compatible with" means that there can exist a 029 * "reference casting conversion" from one type to the other (JLS 5.5.1). 030 * 031 * <p>For example, {@link Collection#contains} would be annotated as follows: 032 * 033 * <pre>{@code 034 * interface Collection<E> { 035 * boolean contains(@CompatibleWith("E") Object o); 036 * } 037 * }</pre> 038 * 039 * <p>To indicate that invocations of {@link Collection#contains} must be passed an argument whose 040 * type is compatible with the generic type argument of the Collection instance: 041 * 042 * <pre>{@code 043 * Collection<String> stringCollection = ...; 044 * boolean shouldBeFalse = stringCollection.contains(42); // BUG! int isn't compatible with String 045 * }</pre> 046 * 047 * <p>Note: currently, this annotation can't be used if the method overrides another method that has 048 * {@code @CompatibleWith} already present. 049 */ 050@Documented 051@Retention(RetentionPolicy.SOURCE) 052@Target(ElementType.PARAMETER) 053public @interface CompatibleWith { 054 String value(); 055}