-- | Builds a call graph of function definitions                           
callGraph' :: ControlPoint DataEnv -> TypedExpr -> CallGraph
callGraph' f (TEApp _ (TEFold _ _) [tag@(TETag _ _ _)]) = callGraph' f tag
callGraph' :: ControlPoint DataEnv -> TypedExpr -> CallGraph
callGraph' f (TEApp _ (TEFold _ _) [tag@(TETag _ _ _)]) = callGraph' f tag
callGraph' f (TEApp _ (TEFold _ _) [tag@(TETag _ _ _)]) = callGraph' f tag