Summary

Two changes proposed:

1. The current specification for Pattern Matching in instanceof allows declaration annotations on the pattern variables, but javac does not currently support them.

2. The specification for Pattern Matching in instanceof has been recently updated to allow the final modifier (with the usual meaning and grammar) on pattern variables; javac needs to be updated to accept them as well.

Problem

Two issues:

1. javac does not handle declaration annotations properly on pattern variables. E.g. the following fails to compile:

   public class A {
    public void test(Object o) {
        if (o instanceof @Deprecated String s) {}
    }
   } 

2. javac does not support a recent change to the specification to allow the final modifier on pattern variables E.g. the following does not compile:

   public class B {
    public void test(Object o) {
        if (o instanceof final String s) {}
    }
   } 

Solution

The JLS will be updated to allow the final modifier on pattern variables. javac will be updated to allow both the final modifier and declaration annotations on pattern variables.

Specification

The full draft specification will be attached. The only non-editorial change compared to state described in JDK-8254235 is that the final modifier is allowed on the pattern variables, with the same grammar and semantics as for local variables.