CheckRealizable

Compute realizability status.

A type T is realizable iff it is inhabited by non-null values. This ensures that its type members have good bounds (in the sense from DOT papers). A type projection T#L is legal if T is realizable, and can be understood as Scala 2's v.L forSome { val v: T }.

In general, a realizable type can have multiple inhabitants, hence it need not be stable (in the sense of Type.isStable).