TypeBox

A type for skolems that are generated during capture conversion. Capture conversion narrows the type of a tree whose type has wildcard arguments. A typical situation is a tree t of type C[_ >: L <: U] and an expected type C[X] where X is an instantiatable type variable. To be able to instantiate X, we cast the tree to type X[$n.CAP] where $n is a fresh skolem type with underlying type TypeBox[L, U].