Introduce com.google.errorprone.annotations.Modifier

for use in `@IncompatibleModifiers` and `@RequiredModifiers`, as an
alternative to `javax.lang.model.element.Modifier` which is not
available at compile-time on Android.

#2122

PiperOrigin-RevId: 375766509

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

@@ -21,14 +21,13 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
-import javax.lang.model.element.Modifier;
 
 /**
  * Annotation declaring that the target annotation is incompatible with any one of the provided
  * modifiers. For example, an annotation declared as:
  *
  * <pre>
- * {@literal @}IncompatibleModifiers(Modifier.PUBLIC)
+ * {@literal @}IncompatibleModifiers(modifier = Modifier.PUBLIC)
  * {@literal @}interface MyAnnotation {}
  * </pre>
  *
@@ -44,12 +43,17 @@
 @Retention(RetentionPolicy.CLASS) // Element's source might not be available during analysis
 @Target(ElementType.ANNOTATION_TYPE)
 public @interface IncompatibleModifiers {
+
+  /** @deprecated use {@link #modifier} instead */
+  @Deprecated
+  javax.lang.model.element.Modifier[] value() default {};
+
   /**
    * The incompatible modifiers. The annotated element is illegal with the presence of any one or
    * more of these modifiers.
    *
    * <p>Empty array has the same effect as not applying this annotation at all; duplicates are
    * allowed but have no effect.
    */
-  Modifier[] value();
+  Modifier[] modifier() default {};
 }

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

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2021 The Error Prone 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.errorprone.annotations;
+
+/**
+ * Modifiers in the Java language, as specified in:
+ *
+ * <ul>
+ *   <li>https://docs.oracle.com/javase/specs/jls/se11/html/jls-8.html#jls-8.1.1
+ *   <li>https://docs.oracle.com/javase/specs/jls/se11/html/jls-8.html#jls-8.3.1
+ *   <li>https://docs.oracle.com/javase/specs/jls/se11/html/jls-8.html#jls-8.4.3
+ *   <li>https://docs.oracle.com/javase/specs/jls/se11/html/jls-9.html#jls-9.4
+ * </ul>
+ */
+public enum Modifier {
+  PUBLIC,
+  PROTECTED,
+  PRIVATE,
+  ABSTRACT,
+  DEFAULT,
+  STATIC,
+  FINAL,
+  TRANSIENT,
+  VOLATILE,
+  SYNCHRONIZED,
+  NATIVE,
+  STRICTFP
+}

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

@@ -21,14 +21,13 @@
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
-import javax.lang.model.element.Modifier;
 
 /**
  * Annotation declaring that the target annotation requires all the specified modifiers. For
  * example, an annotation declared as:
  *
  * <pre>
- * {@literal @}RequiredModifiers(Modifier.PUBLIC)
+ * {@literal @}RequiredModifiers(modifier = Modifier.PUBLIC)
  * {@literal @}interface MyAnnotation {}
  * </pre>
  *
@@ -44,12 +43,17 @@
 @Retention(RetentionPolicy.CLASS) // Element's source might not be available during analysis
 @Target(ElementType.ANNOTATION_TYPE)
 public @interface RequiredModifiers {
+
+  /** @deprecated use {@link #modifier} instead */
+  @Deprecated
+  javax.lang.model.element.Modifier[] value() default {};
+
   /**
    * The required modifiers. The annotated element is illegal if any one or more of these modifiers
    * are absent.
    *
    * <p>Empty array has the same effect as not applying this annotation at all; duplicates are
    * allowed but have no effect.
    */
-  Modifier[] value();
+  Modifier[] modifier() default {};
 }