8338700: AttributeMapper type parameter should be bounded by Attribute

Reviewed-by: asotona

Author: liach

src/java.base/share/classes/java/lang/classfile/AttributeMapper.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2022, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2022, 2024, 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
@@ -40,7 +40,7 @@
  * @since 22
  */
 @PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
-public interface AttributeMapper<A> {
+public interface AttributeMapper<A extends Attribute<A>> {
 
     /**
      * Attribute stability indicator

src/java.base/share/classes/java/lang/classfile/package-info.java

@@ -147,7 +147,7 @@
  * ClassReader, int)} method for mapping from the classfile format
  * to an attribute instance, and the
  * {@link java.lang.classfile.AttributeMapper#writeAttribute(java.lang.classfile.BufWriter,
- * java.lang.Object)} method for mapping back to the classfile format.  It also
+ * java.lang.classfile.Attribute)} method for mapping back to the classfile format.  It also
  * contains metadata including the attribute name, the set of classfile entities
  * where the attribute is applicable, and whether multiple attributes of the
  * same kind are allowed on a single entity.

src/java.base/share/classes/jdk/internal/classfile/impl/AttributeHolder.java

@@ -54,7 +54,7 @@ public void writeTo(BufWriterImpl buf) {
     }
 
     @SuppressWarnings("unchecked")
-    <A> A get(AttributeMapper<A> am) {
+    <A extends Attribute<A>> A get(AttributeMapper<A> am) {
         for (Attribute<?> a : attributes)
             if (a.attributeMapper() == am)
                 return (A)a;

src/java.base/share/classes/jdk/internal/classfile/impl/BoundAttribute.java

@@ -148,7 +148,7 @@ public static List<Attribute<?>> readAttributes(AttributedElement enclosing, Cla
                 mapper = customAttributes.apply(name);
             }
             if (mapper != null) {
-                filled.add((Attribute<?>) Objects.requireNonNull(mapper.readAttribute(enclosing, reader, p)));
+                filled.add(Objects.requireNonNull(mapper.readAttribute(enclosing, reader, p)));
             } else {
                 AttributeMapper<UnknownAttribute> fakeMapper = new AttributeMapper<>() {
                     @Override

src/java.base/share/classes/jdk/internal/classfile/impl/Util.java

@@ -224,7 +224,7 @@ public static MethodTypeDesc methodTypeSymbol(NameAndTypeEntry nat) {
     }
 
     @SuppressWarnings("unchecked")
-    private static <T> void writeAttribute(BufWriterImpl writer, Attribute<?> attr) {
+    private static <T extends Attribute<T>> void writeAttribute(BufWriterImpl writer, Attribute<?> attr) {
         if (attr instanceof CustomAttribute<?> ca) {
             var mapper = (AttributeMapper<T>) ca.attributeMapper();
             mapper.writeAttribute(writer, (T) ca);