src/test/ui/rfcs/rfc-2528-type-changing-struct-update/type-generic-update.rs

   1 #![feature(type_changing_struct_update)]
   2 #![allow(incomplete_features)]
   3
   4 struct Machine<'a, S, M> {
   5     state: S,
   6     message: M,
   7     lt_str: &'a str,
   8     common_field: i32,
   9 }
  10
  11 struct State1;
  12 struct State2;
  13
  14 struct Message1;
  15 struct Message2;
  16
  17 fn update() {
  18     let m1: Machine<State1, Message1> = Machine {
  19         state: State1,
  20         message: Message1,
  21         lt_str: "hello",
  22         common_field: 2,
  23     };
  24     // single type update
  25     let m2: Machine<State2, Message1> = Machine {
  26         state: State2,
  27         ..m1
  28     };
  29     // multiple type update
  30     let m3: Machine<State2, Message2> = Machine {
  31         state: State2,
  32         message: Message2,
  33         ..m1
  34     };
  35 }
  36
  37 fn fail_update() {
  38     let m1: Machine<f64, f64> = Machine {
  39         state: 3.2,
  40         message: 6.4,
  41         lt_str: "hello",
  42         common_field: 2,
  43     };
  44     // single type update fail
  45     let m2: Machine<i32, f64> = Machine {
  46         ..m1
  47         //~^ ERROR mismatched types [E0308]
  48     };
  49     // multiple type update fail
  50     let m3 = Machine::<i32, i32> {
  51         ..m1
  52         //~^ ERROR mismatched types [E0308]
  53     };
  54 }
  55
  56 fn main() {}