8263763: Synthetic constructor parameters of enum are not considered for annotation indices

Reviewed-by: darcy, jfranck

src/java.base/share/classes/java/lang/reflect/Constructor.java

@@ -605,9 +605,14 @@ public final class Constructor<T> extends Executable {
     }
 
     @Override
-    boolean handleParameterNumberMismatch(int resultLength, int numParameters) {
+    boolean handleParameterNumberMismatch(int resultLength, Class<?>[] parameterTypes) {
+        int numParameters = parameterTypes.length;
         Class<?> declaringClass = getDeclaringClass();
-        if (declaringClass.isEnum() ||
+        if (declaringClass.isEnum()) {
+            return resultLength + 2 == numParameters &&
+                    parameterTypes[0] == String.class &&
+                    parameterTypes[1] == int.class;
+        } else if (
             declaringClass.isAnonymousClass() ||
             declaringClass.isLocalClass() )
             return false; // Can't do reliable parameter counting

src/java.base/share/classes/java/lang/reflect/Executable.java

@@ -566,17 +566,19 @@ public abstract class Executable extends AccessibleObject
         Annotation[][] result = parseParameterAnnotations(parameterAnnotations);
 
         if (result.length != numParameters &&
-            handleParameterNumberMismatch(result.length, numParameters)) {
-            Annotation[][] tmp = new Annotation[result.length+1][];
-            // Shift annotations down one to account for an implicit leading parameter
-            System.arraycopy(result, 0, tmp, 1, result.length);
-            tmp[0] = new Annotation[0];
+            handleParameterNumberMismatch(result.length, parameterTypes)) {
+            Annotation[][] tmp = new Annotation[numParameters][];
+            // Shift annotations down to account for any implicit leading parameters
+            System.arraycopy(result, 0, tmp, numParameters - result.length, result.length);
+            for (int i = 0; i < numParameters - result.length; i++) {
+                tmp[i] = new Annotation[0];
+            }
             result = tmp;
         }
         return result;
     }
 
-    abstract boolean handleParameterNumberMismatch(int resultLength, int numParameters);
+    abstract boolean handleParameterNumberMismatch(int resultLength, Class<?>[] parameterTypes);
 
     /**
      * {@inheritDoc}

src/java.base/share/classes/java/lang/reflect/Method.java

@@ -760,7 +760,7 @@ public final class Method extends Executable {
     }
 
     @Override
-    boolean handleParameterNumberMismatch(int resultLength, int numParameters) {
+    boolean handleParameterNumberMismatch(int resultLength, Class<?>[] parameterTypes) {
         throw new AnnotationFormatError("Parameter annotations don't match number of parameters");
     }
 }

test/jdk/java/lang/annotation/EnumConstructorAnnotation.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 8263763
+ * @summary Check that annotations on an enum constructor are indexed correctly.
+ */
+
+import java.lang.annotation.Annotation;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.reflect.Constructor;
+import java.util.Arrays;
+
+public class EnumConstructorAnnotation {
+
+    public static void main(String[] args) {
+        Constructor<?> c = SampleEnum.class.getDeclaredConstructors()[0];
+        Annotation[] a1 = c.getParameters()[2].getAnnotations(), a2 = c.getParameterAnnotations()[2];
+        for (Annotation[] a : Arrays.asList(a1, a2)) {
+            if (a.length != 1) {
+                throw new RuntimeException("Unexpected length " + a.length);
+            } else if (a[0].annotationType() != SampleAnnotation.class) {
+                throw new RuntimeException("Unexpected type " + a[0]);
+            }
+        }
+    }
+
+    enum SampleEnum {
+        INSTANCE("foo");
+        SampleEnum(@SampleAnnotation String value) { }
+    }
+
+    @Retention(RetentionPolicy.RUNTIME)
+    @interface SampleAnnotation { }
+}