Summary

Update Class::isRecord to only return true for classes that are final.

Problem

The removal of non-specified JVM checks on classes with a Record Attribute (see JDK-8255342), has resulted in more types of loadable classes that may contain a Record Attribute. Since these checks are not performed by the JVM anymore, Class::isRecord, and by extension Class::getRecordComponents, may return true or component values, respectively, for classes that are not well-formed record classes (as per the JLS), .e.g. non-final or abstract classes, that contain a record Attribute.

Solution

Core Reflection, Class::isRecord, already asserts checks that the JVM does not, e.g. that the direct superclass is java.lang.Record.

Some points from the Java Language Specification for record classes:

1. It is a compile-time error if a record declaration has the modifier abstract.
2. A record declaration is implicitly final.
3. The direct superclass type of a record class is Record.

Class::isRecord already ensures no.3. This issue proposes to add explicit checks in Core Reflection to ensure #1 and #2, since the JVM now allows such classes that contain a Record Attribute to be loaded.

Note: asserting that a class is final is sufficient, as it implies that the class it non-abstract - an assertion guaranteed by the JVM.

Specification

java.lang.Class:

   /**
    * Returns {@code true} if and only if this class is a record class.
    *
    * <p> The {@linkplain #getSuperclass() direct superclass} of a record
-   * class is {@code java.lang.Record}. A record class has (possibly zero)
-   * record components, that is, {@link #getRecordComponents()} returns a
-   * non-null value.
+   * class is {@code java.lang.Record}. A record class is {@linkplain
+   * Modifier#FINAL final}. A record class has (possibly zero) record
+   * components; {@link #getRecordComponents()} returns a non-null but
+   * possibly empty value for a record.
    *
    * <p> Note that class {@link Record} is not a record type and thus invoking
    * this method on class {@code Record} returns {@code false}.
    *
    * @return true if and only if this class is a record class, otherwise false
    * @jls 8.10 Record Types
    * @since 16
    */
   public boolean isRecord() { ... }