FPFn4
FP function interface with 4 arguments.
interface FPFn4 <Result, Arg4, Arg3, Arg2, Arg1> {
(): FPFn4<Result, Arg4, Arg3, Arg2, Arg1>;
(arg4: Arg4): FPFn3<Result, Arg3, Arg2, Arg1>;
(
}arg4: Arg4,
arg3: Arg3,
arg2: Arg2,
arg1: Arg1,
): Result;