Add Elements.getEnumConstantBody

Summary

For enum constants with specialized class bodies, the JLS mandates a translation into an anonymous subclass. The javax.lang.model API does not expose such subclasses when present.

Problem

In terms of providing as full a model of the language as reasonable, the lack of information on such class bodies is a gap. This gap has come up in writing facilities in various areas, including lint checks and fuller javadoc support.

Solution

Add a method to the Elements interface to provide the missing functionality. A default method is added to provide a nominal implementation, as usual.

Specification

diff --git a/src/java.compiler/share/classes/javax/lang/model/util/Elements.java b/src/java.compiler/share/classes/javax/lang/model/util/Elements.java
index d3326ba7018f..0b1e49768184 100644
--- a/src/java.compiler/share/classes/javax/lang/model/util/Elements.java
+++ b/src/java.compiler/share/classes/javax/lang/model/util/Elements.java
@@ -758,6 +758,30 @@ default boolean isAutomaticModule(ModuleElement module) {
         return false;
     }

+    /**
+     * {@return the class body of an {@code enum} constant if the
+     * argument is an {@code enum} constant declared with an optional
+     * class body, {@code null} otherwise}
+     *
+     * @implSpec
+     * The default implementation of this method throws {@code
+     * UnsupportedOperationException} if the argument is an {@code
+     * enum} constant and throws an {@code IllegalArgumentException}
+     * if it is not.
+     *
+     * @param enumConstant an enum constant
+     * @throws IllegalArgumentException if the argument is not an {@code enum} constant
+     * @jls 8.9.1 Enum Constants
+     * @since 22
+     */
+    default TypeElement getEnumConstantBody(VariableElement enumConstant) {
+        if (enumConstant.getKind() == ElementKind.ENUM_CONSTANT) {
+            throw new UnsupportedOperationException();
+        } else {
+            throw new IllegalArgumentException("Argument not an enum constant");
+        }
+    }
+
     /**
      * Returns the record component for the given accessor. Returns
      * {@code null} if the given method is not a record component