Lambda the Ultimate

The essence of ML type inference is an expanded version of Chapter 10 of the beloved Advanced Topics in Types and Programming Languages. It weighs in as the heaviest non-dissertation, non-book academic paper I've ever seen, but it's still a great introduction to HM type inference with some extensions.

The extensions are based on contraints, and are closely related to HM(X) and Chameleon. Along the way, the authors deal with row types, equirecursive types, and subtyping. Fun for the whole family!