Polymorphic Subtyping for Effect Analysis: The Static Semantics

The integration of polymorphism (in the style of the ML let-construct), subtyping, and effects (modelling assignment or communication) into one common type system has proved remarkably difficult. One line of research has succeeded in integrating polymorphism and subtyping; adding effects in a straightforward way results in a semantically unsound system. Another line of research has succeeded in integrating polymorphism, effects, and subeffecting; adding subtyping in a straightforward way invalidates the construction of the inference algorithm. This paper integrates all of polymorphism, effects, and subtyping into an annotated type and effect system for Concurrent ML and shows that the resulting system is a conservative extension of the ML type system.