I've been using piqi for quite a while and it's done wonders for me.

Lately though, I've had some issues with transforming some types provided by another library into a piqi representation.

Essentially, I'm at a crossroads where I'm running into a compile error, and I'm not sure how to fix it. Here's the root of my problem:

Error: This expression has type Stmt_piqi.stmt list list

       but an expression was expected of type

         Bapservice_piqi.Bapservice_piqi.lifted_region =

           Bapservice_piqi.Bapservice_piqi.stmt_list list

       Type Stmt_piqi.stmt list is not compatible with type

         Bapservice_piqi.Bapservice_piqi.stmt_list =

           Bapservice_piqi.Bapservice_piqi.stmt list 

       Type Stmt_piqi.stmt is not compatible with type

         Bapservice_piqi.Bapservice_piqi.stmt =

           [ `cpuexn of Bapservice_piqi.Bapservice_piqi.cpuexn

           | `if_stmt of Bapservice_piqi.Bapservice_piqi.if_stmt

           | `jmp of Bapservice_piqi.Bapservice_piqi.jmp

           | `move of Bapservice_piqi.Bapservice_piqi.move

           | `special of Bapservice_piqi.Bapservice_piqi.special

           | `while_stmt of Bapservice_piqi.Bapservice_piqi.while_stmt ]

lifted_region is defined in my piqi file as a stmt list list (a list of instructions). Here's the part that I don't know: in piqi do I import the module instead of including it in order to get the compiler to see that the types are equivalent? 

(because they are, this is very much like debugging a phantom type error. Stmt_piqi.stmt is the same as Bapservice_piqi.stmt).

My thinking with the above question is that if I import the module in piqi, then the piqi command will *not* generate a whole new ml, different entirely to the ml that was compiled and included in the library that I'm using, bap (it currently *is*). In that case, the types will be equivalent and everything will compile nicely.

But I attempted to import the module in my piqi file, and that results in some compile error that I don't know how to solve:

Unbound module Stmt_piqi. 

Naturally, in my makefile for generating ml of piqi encoder/decoder ocaml modules, I have an include that points to the folder that contains the bap stmt.piqi file. So the piqi ocaml command succeeds, but now I need to tell ocaml how to resolve the stmt_piqi module (compiled away in bap.serialization). I'm using oasis, and I already have bap.serialization in my depends, and the generated piqi ml file is auto detected and the correct bap.serialization is propagated through as a specified package on the command line.

How do I get the compiler to either see type equivalence of the Bapservice_piqi.stmt type or to know where to get the Stmt_piqi module?