Inferência de tipos com suporte para sobrecarga baseada no sistema CT

This work discusses the problem of type inference in the presence of overloading, making a revision of type system CT . This system is an extension of the wellknown Damas-Milner system with support for overloading, where constraints are used in polymorphic types to indicate restrictions on the instantiation of these types, with respect to type assumptions of overloaded symbols that are available in the relevant typing context. Type inference in this system involves a solution to the problem of constraint-set satisfiability in a given typing context, that is, the problem of deciding whether a given set of constraints in a polymorphic type is considered valid (is satisfied) or not, in a given typing context. Over-restrictive overloading policies have been adopted in order to guarantee the decidibility of this problem. System CT adopts an overloading policy that is much less restrictive than those of similar type systems. The main contribuitions of this work are the following: a formal definition of the problem of constraint-set satisfiability that is independent of (the rules used in) a type system, the definition of an algorithm for solving this problem and the implementation of a prototype of this algorithm that indicates that the adoption of a less restrictive overloading policy can work well in practice. In tests with this prototype, no situation was detected where the satisfiability could not be decided. In this cases a user configurable iteration limit is used in order to stop the process and reject the expression, indicating a type error.