Add a version of @CheckReturnValue to ErrorProne

RELNOTES: Add a version of @CheckReturnValue to ErrorProne

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=175564025

annotations/src/main/java/com/google/errorprone/annotations/CheckReturnValue.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2017 Google Inc. All Rights Reserved.
+ *
+ * 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.errorprone.annotations;
+
+import static java.lang.annotation.ElementType.CONSTRUCTOR;
+import static java.lang.annotation.ElementType.METHOD;
+import static java.lang.annotation.ElementType.PACKAGE;
+import static java.lang.annotation.ElementType.TYPE;
+import static java.lang.annotation.RetentionPolicy.RUNTIME;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.Retention;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that the return value of the annotated method must be checked. An error is triggered
+ * when one of these methods is called but the result is not used.
+ *
+ * <p>{@code @CheckReturnValue} may be applied to a class or package to indicate that all methods in
+ * that class or package must have their return values checked. For convenience, we provide an
+ * annotation, {@link CanIgnoreReturnValue}, to exempt specific methods or classes from this
+ * behavior.
+ */
+@Documented
+@Target({METHOD, CONSTRUCTOR, TYPE, PACKAGE})
+@Retention(RUNTIME)
+public @interface CheckReturnValue {}

core/src/main/java/com/google/errorprone/bugpatterns/CheckReturnValue.java

@@ -120,8 +120,7 @@ public Matcher<ExpressionTree> specializedMatcher() {
       "@CheckReturnValue and @CanIgnoreReturnValue cannot both be applied to the same %s";
 
   /**
-   * Validate {@link javax.annotation.CheckReturnValue} and {@link CanIgnoreReturnValue} usage on
-   * methods.
+   * Validate {@code @CheckReturnValue} and {@link CanIgnoreReturnValue} usage on methods.
    *
    * <p>The annotations should not both be appled to the same method.
    *

core/src/test/java/com/google/errorprone/bugpatterns/testdata/CheckReturnValuePositiveCases.java

@@ -24,7 +24,7 @@ public class CheckReturnValuePositiveCases {
 
   IntValue intValue = new IntValue(0);
 
-  @CheckReturnValue
+  @javax.annotation.CheckReturnValue
   private int increment(int bar) {
     return bar + 1;
   }
@@ -118,7 +118,7 @@ public IntValue(int i) {
       this.i = i;
     }
 
-    @CheckReturnValue
+    @javax.annotation.CheckReturnValue
     public IntValue increment() {
       return new IntValue(i + 1);
     }
@@ -135,15 +135,15 @@ public void increment3() {
   }
 
   private static class MyObject {
-    @CheckReturnValue
+    @javax.annotation.CheckReturnValue
     MyObject() {}
   }
 
   private abstract static class LB1<A> {}
 
   private static class LB2<A> extends LB1<A> {
 
-    @CheckReturnValue
+    @javax.annotation.CheckReturnValue
     public static <T> LB2<T> lb1() {
       return new LB2<T>();
     }
@@ -154,4 +154,16 @@ public static <T> LB2<T> lb2() {
       return lb1();
     }
   }
+
+  private static class ErrorProneAnnotation {
+    @com.google.errorprone.annotations.CheckReturnValue
+    public static int check() {
+      return 1;
+    }
+
+    public static void ignoresCheck() {
+      // BUG: Diagnostic contains: remove this line
+      check();
+    }
+  }
 }