Typability and type inference in atomic polymorphism

It is well-known that typability, type inhabitation and type inference are undecidable in the Girard-Reynolds polymorphic system F. It has recently been proven that type inhabitation remains undecidable even in the predicative fragment of system F in which all universal instantiations have an atomic witness (system Fat). In this paper we analyze typability and type inference in Curry style variants of system Fat and show that typability is decidable and that there is an algorithm for type inference which is capable of dealing with non-redundancy constraints.The second author acknowledges the support of FCT — Fundação para a Ciência e a Tecnologia under the projects UIDB/04561/2020, UIDB/00408/2020 and UIDP/00408/2020, and she is also grateful to CMAFcIO — Centro de Matemática, Aplicações Fundamentais e Investigação Operacional and to LASIGE — Computer Science and Engineering Research Centre (Universidade de Lisboa).