Type-variable references from local interface declaration

[Tagir Valeev]

Same with records. For some reason I thought I checked this before,
but this code is compilable both in 14-preview and 15-preview, which
looks incorrect:

class LocalRecord {
  static <U> void test() {
    record R() {
      U get() {return null;}
    }
  }
}

With best regards,
Tagir Valeev.

On Mon, Jun 15, 2020 at 6:45 PM Tagir Valeev <amaembo at gmail.com> wrote:
>
> Hello!
>
> The same problem appears for local enums as well. And, I believe, it
> causes type system unsoundness:
>
> class LocalEnum {
>   static <U> U getAndSet(U u) {
>     enum X {
>       A;
>       U u;
>     }
>     U old = X.A.u;
>     X.A.u = u;
>     return old;
>   }
>
>   public static void main(String[] args) {
>     String s = getAndSet("foo");
>     Integer i = getAndSet(123);
>   }
> }
>
> This code can be compiled without error or warning, yet it produces
> ClassCastException when executed.
>
> With best regards,
> Tagir Valeev.
>
> On Mon, Jun 15, 2020 at 6:38 PM Tagir Valeev <amaembo at gmail.com> wrote:
> >
> > Hello!
> >
> > The spec draft for local interfaces and enums [1] tells that it's
> > illegal to refer to the enclosing method type parameter from the local
> > interface. Here's a simplified sample from the spec:
> >
> > class Box<T> {
> >     static <U> Box<U> make(U val) {
> >         interface Checker {
> >             void check(U val); // compile-time error
> >         }
> >         return null;
> >     }
> > }
> >
> > However, it's successfully compilable using javac 15-ea+26-1287. I
> > believe, either spec or implementation should be adjusted.
> >
> > With best regards,
> > Tagir Valeev.
> >
> > [1] http://cr.openjdk.java.net/~gbierman/jep384/jep384-20200506/specs/local-statics-jls.html#jls-6.5.5.1