Metamodel version of ProducedType.getSupertype(TypeDeclaration)

[tombentley]

Currently although you can ask a ceylon.language.meta.model::Type whether it is a subtype of another Type, you cannot get the principal instantiation of that other type that it's a subtype of. In other words we don't have the metamodel version of the typechecker's ProducedType.getSupertype(TypeDeclaration).

The main impediment to resolving this is needing to implement the whole algorithm for computing principal instantiations in Ceylon. (We could implement this today for the JVM, but the metamodel needs to work on JS too).

This came up here.

[gavinking]

Note: to implement this for any Type is perhaps a bit for work. To implement it just for ClassOrInterface should be pretty trivial.

[gavinking]

@chochos, thoughts?

[chochos]

Right, doing it only for ClassOrInterface shouldn't be too hard. But is it useful?

OTOH, can we really implement the algorithm @tombentley mentions, completely in Ceylon, using the existing metamodel stuff? Perhaps if there are only a couple of things that need to be native, we can encapsule them in separate native methods, although I don't know if native compilation is working already for JVM.

[FroMage]

This sounds too hard, let's move it to the next release.