There is no easy way to find the functions which returns a specific data type t

For example, there is no easy way to list functions which return Unix.file_descr.

_ -> Unix.file_descr just shows functions with arity 1 immediately. It displays Unix.openfile but much later after various polymorphic functions. There are two issues:

• Type instantiation of target type variables may not be a very good idea
• We should have a way to express "arbitrary number of fucntion arguments" like ... -> file_descr

Type instantiation of target type variables is currently disabled.