Type Inference with Nonstructural Subtyping

We present an O(n^3) time type inference algorithm for a typesystem with a largest type !, a smallest type ?, and the usual orderingbetween function types. The algorithm infers type annotations ofminimal size, and it works equally well for recursive types. For theproblem of typability, our algorithm is simpler than the one of Kozen,Palsberg, and Schwartzbach for type inference without ?. This maybe surprising, especially because the system with ? is strictly morepowerful