F2_1<Result, State1, State2, Param1> typedef
F2_1<Result, State1, State2, Param1> =
R2_1<Result, Param1> Function(State1, State2)
Implementation
typedef F2_1<Result, State1, State2, Param1> = R2_1<Result, Param1> Function(
State1,
State2,
);