TYPE INFERENCE WITH PARTIAL TYPES

As a partial solution to the problem of combining static and dynamic typing in a language with parametric polymorphism, this paper introduces a new form of type expressions which represent partial type information. These expressions are meant to capture the type information statically derivable from heterogeneous objects. The new ground types form a semilattice of subtypes and require type inference based on inclusion constraints. We discuss the existence and form of principal types under this extension and present a semi-decision procedure for the complete type inference problem.