`module type S : sig ... end`

Suffix of a normal trace: just sinks and passthroughs, but no sources

`module MakeSink : functor (TraceElem : InferModules.TraceElem.S) -> InferModules.Sink.S with module Kind = TraceElem.Kind and type t = TraceElem.t`
`module Make : functor (TraceElem : InferModules.TraceElem.S) -> S with module Source = InferModules.Source.Dummy and module Sink = MakeSink(TraceElem)`