error.ml

type something = | Something 'a :something;

module type ChildType = {let makeSomething: int => something;};

let module MakeThing (ChildA: ChildType) (ChildB: ChildType) => {
  type childArg = | A int | B int;
  let doThing arg =>
    switch arg {
    | A n => ChildA.makeSomething 10
    | B n => ChildB.makeSomething 5
    };
};

let module Result =
  (MakeThing 
    { let makeSomething _ => Something "string"; }
    { let makeSomething _ => Something "otherSTring"; });

let x = Result.doThing (Result.A 10);
switch x {
  | Something z => print_endline z
};