8247444: Trust final fields in records

Co-authored-by: Christoph Dreis <christoph.dreis@freenet.de>
Reviewed-by: jrose, dholmes, forax, coleenp, vlivanov

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

@@ -177,10 +177,16 @@ public class AccessibleObject implements AnnotatedElement {
      * to the caller's module. </p>
      *
      * <p> This method cannot be used to enable {@linkplain Field#set <em>write</em>}
-     * access to a final field declared in a {@linkplain Class#isHidden() hidden class},
-     * since such fields are not modifiable.  The {@code accessible} flag when
-     * {@code true} suppresses Java language access control checks to only
-     * enable {@linkplain Field#get <em>read</em>} access to such fields.
+     * access to a <em>non-modifiable</em> final field.  The following fields
+     * are non-modifiable:
+     * <ul>
+     * <li>static final fields declared in any class or interface</li>
+     * <li>final fields declared in a {@linkplain Class#isHidden() hidden class}</li>
+     * <li>final fields declared in a {@linkplain Class#isRecord() record}</li>
+     * </ul>
+     * <p> The {@code accessible} flag when {@code true} suppresses Java language access
+     * control checks to only enable {@linkplain Field#get <em>read</em>} access to
+     * these non-modifiable final fields.
      *
      * <p> If there is a security manager, its
      * {@code checkPermission} method is first called with a

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

@@ -72,6 +72,7 @@ class Field extends AccessibleObject implements Member {
     private String              name;
     private Class<?>            type;
     private int                 modifiers;
+    private boolean             trustedFinal;
     // Generics and annotations support
     private transient String    signature;
     // generic info repository; lazily initialized
@@ -119,6 +120,7 @@ class Field extends AccessibleObject implements Member {
           String name,
           Class<?> type,
           int modifiers,
+          boolean trustedFinal,
           int slot,
           String signature,
           byte[] annotations)
@@ -127,6 +129,7 @@ class Field extends AccessibleObject implements Member {
         this.name = name;
         this.type = type;
         this.modifiers = modifiers;
+        this.trustedFinal = trustedFinal;
         this.slot = slot;
         this.signature = signature;
         this.annotations = annotations;
@@ -148,7 +151,7 @@ class Field extends AccessibleObject implements Member {
         if (this.root != null)
             throw new IllegalArgumentException("Can not copy a non-root Field");
 
-        Field res = new Field(clazz, name, type, modifiers, slot, signature, annotations);
+        Field res = new Field(clazz, name, type, modifiers, trustedFinal, slot, signature, annotations);
         res.root = this;
         // Might as well eagerly propagate this if already present
         res.fieldAccessor = fieldAccessor;
@@ -728,7 +731,9 @@ class Field extends AccessibleObject implements Member {
      *     this {@code Field} object;</li>
      * <li>the field is non-static; and</li>
      * <li>the field's declaring class is not a {@linkplain Class#isHidden()
-     *     hidden class}.</li>
+     *     hidden class}; and</li>
+     * <li>the field's declaring class is not a {@linkplain Class#isRecord()
+     *     record class}.</li>
      * </ul>
      * If any of the above checks is not met, this method throws an
      * {@code IllegalAccessException}.
@@ -1145,10 +1150,14 @@ class Field extends AccessibleObject implements Member {
     }
 
     @Override
-    Field getRoot() {
+    /* package-private */ Field getRoot() {
         return root;
     }
 
+    /* package-private */ boolean isTrustedFinal() {
+        return trustedFinal;
+    }
+
     /**
      * {@inheritDoc}
      *

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

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2020, 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
@@ -118,6 +118,10 @@ class ReflectAccess implements jdk.internal.access.JavaLangReflectAccess {
         return (T) obj.getRoot();
     }
 
+    public boolean isTrustedFinalField(Field f) {
+        return f.isTrustedFinal();
+    }
+
     public <T> T newInstance(Constructor<T> ctor, Object[] args, Class<?> caller)
         throws IllegalAccessException, InstantiationException, InvocationTargetException
     {