Predicative compilation and full monomorphization

Determine whether choosing the predicative size rule for function types in Hippogriff yields a system that can be fully monomorphized during compilation by statically tracking the implementations of functions with type arguments.

Background

Hippogriff can be made impredicative or predicative by changing how the size of a function type is determined. The current implementation adopts the impredicative choice because its semantics are modeled using System F.

The paper identifies, conjecturally, a potential consequence of the predicative alternative: functions with type arguments might be fully monomorphized during compilation because their implementations could be tracked statically. Establishing whether this compilation property actually follows from the predicative design remains unresolved.

References

However, conjecturally the predicative choice could lead to a system that could be fully monomorphized during compilation, essentially because we can statically track the implementations of functions with type arguments.

— Hippogriff: a semantic approach to uniting core and modules  (2608.19728 - Lynch et al., 20 Aug 2026) in Section 3, subsection “Impredicativity”