Summary:
It is (now?) the case that `[%sexp_of: type_name]` generates just
`sexp_of_type_name`, rather than expanding `type_name` to its
definition and generating a conversion function for that. Hence, when
such cases appear within `let rec sexp_of_type_name`, they get
captured, sometimes leading to divergence.
This diff fixes this by manually expanding such types into their
definitions.
Reviewed By: ngorogiannis
Differential Revision: D15314736
fbshipit-source-id: 716fff7cc
Josh Berdine
9a62554322