tests/ui/issues/issue-20055-box-trait.rs

   1 // run-pass
   2 // See Issues #20055 and #21695.
   3
   4 // We are checking here that the temporaries `Box<[i8, k]>`, for `k`
   5 // in 1, 2, 3, 4, that are induced by the match expression are
   6 // properly handled, in that only *one* will be initialized by
   7 // whichever arm is run, and subsequently dropped at the end of the
   8 // statement surrounding the `match`.
   9
  10 trait Boo {
  11     fn dummy(&self) { }
  12 }
  13
  14 impl Boo for [i8; 1] { }
  15 impl Boo for [i8; 2] { }
  16 impl Boo for [i8; 3] { }
  17 impl Boo for [i8; 4] { }
  18
  19 pub fn foo(box_1: fn () -> Box<[i8; 1]>,
  20            box_2: fn () -> Box<[i8; 2]>,
  21            box_3: fn () -> Box<[i8; 3]>,
  22            box_4: fn () -> Box<[i8; 4]>,
  23             ) {
  24     println!("Hello World 1");
  25     let _: Box<dyn Boo> = match 3 {
  26         1 => box_1(),
  27         2 => box_2(),
  28         3 => box_3(),
  29         _ => box_4(),
  30     };
  31     println!("Hello World 2");
  32 }
  33
  34 pub fn main() {
  35     fn box_1() -> Box<[i8; 1]> { Box::new( [1; 1] ) }
  36     fn box_2() -> Box<[i8; 2]> { Box::new( [1; 2] ) }
  37     fn box_3() -> Box<[i8; 3]> { Box::new( [1; 3] ) }
  38     fn box_4() -> Box<[i8; 4]> { Box::new( [1; 4] ) }
  39
  40     foo(box_1, box_2, box_3, box_4);
  41 }