RFR: JDK-8283416: Update java.lang.invoke.MethodHandle to use sealed classes

[Athijegannathan Sundararajan]

On Sun, 20 Mar 2022 21:31:15 GMT, Joe Darcy <darcy at openjdk.org> wrote:

> Small refactoring to use sealed classes in the MethodHandle implementation hierarchy.
> 
> DelegatingMethodHandle is non-sealed rather than sealed since it has two subclasses, one defined as a nested class and only a separate type in the same package. The permits clause does not allow listed those two kinds of subclasses.
> 
> Please also review the corresponding CSR https://bugs.openjdk.java.net/browse/JDK-8283434

Hmm.. I tried the following example:

$ cat com/acme/X.java
package com.acme;

// We can omit permits clause if all the subclasses are in the same compilation unit.
// But that's applicable here as two subclasses "Z", "P.Q" are outside the compilation unit.
// So we use explicit permits clause that lists all the subclasses.

public sealed class X 
   permits X.Y, W, Z, P.Q {
   final class Y extends X {}
}

final class W extends X {}

$ cat com/acme/Z.java
package com.acme;

final class Z extends X {
}

$ cat com/acme/P.java 
package com.acme;

class P {
   final class Q extends X {}
}

$ javac com/acme/*.java

is fine. Am I missing something?

-------------

PR: https://git.openjdk.java.net/jdk/pull/7881