JEP 405 Record Patterns and Backwards Compatible Changes

[Nathan Walker]

Currently in Java 18 we can make backwards compatible changes to the
contents of a record.

Given:

   record Point(int x, int y){ }

We can add point z with:

   record Point(int x, int y, int z) {

      @Deprecated
      Point(int x, int y){ this(x, y, 0); }
   }

Or given:

   record Point(int x, int y, int z){ }

We can remove point z with:

   record Point(int x, int y) {

      @Deprecated
      Point(int x, int y, int z){ this(x, y); }

      @Deprecated
      public z(){ return 0; }
   }

If they are marked serializable then even the serialized forms maintain
backwards compatibility, with the z value in the first example being
defaulted to 0 during deserialization, and the z in the second example
being ignored during deserialization.

But if I understood JEP 405 correctly, a record pattern depends on matching
the exact record components.  So is there a way in JEP 405 to change a
record's components without breaking everywhere that is using the record in
a pattern match statement?  I would be concerned about using records in any
public API if every minor change to a record's structure will require a new
major version release under semantic versioning rules.

Thanks for your time.