Support extension methods on a specialized version of a raw type

In addition to generic types, also support extension methods on specific parameterized instances of generic types. For example:

package extensions.java.util.List;

import manifold.ext.api.Extension;
import manifold.ext.api.This;
import java.util.List;

@Extension
public class MyListOfStringExt {
  public static String foo(@This List<String>  thiz) {
    return thiz.get( 0 );
  }
}

The idea is the type variables are inferred from the @This parameter type and, thus, only apply accordingly. An alternative format follows more closely with a normal extension method on a generic class, which specifies the type var. This one has the advantage of supporting covariance:

  public static <E extends String> String foo(@This List<E>  thiz) {
    return thiz.get( 0 );
  }

Should be straightforward to implement in Manifold. The challenge is probably more with Intellij to get code completion to filter out such extension methods when they don’t apply.

[rsmckinney]

Right… if you want contravariance on the return type, you’ll have to use a non-extension method for that. This is a case that will be supported when this issue (#7) is implemented.

[WilliamStone]

Glad to know that. Thanks!