Instead of
> <@ fun x (g, f) -> 3 @> |> source;;
val it : string =
"fun x tupledArg -> let g = (let item1,_ = tupledArg in item1) in let f = (let _,item2 = tupledArg in item2) in 3"
should be
> <@ fun x (g,f) -> 3 @> |> source;;
val it : string = "fun x (g, f) -> 3"