src/test/ui/consts/const-eval/union-const-eval-field.rs

   1 // only-x86_64
   2
   3 type Field1 = i32;
   4 type Field2 = f32;
   5 type Field3 = i64;
   6
   7 #[repr(C)]
   8 union DummyUnion {
   9     field1: Field1,
  10     field2: Field2,
  11     field3: Field3,
  12 }
  13
  14 const FLOAT1_AS_I32: i32 = 1065353216;
  15 const UNION: DummyUnion = DummyUnion { field1: FLOAT1_AS_I32 };
  16
  17 const fn read_field1() -> Field1 {
  18     const FIELD1: Field1 = unsafe { UNION.field1 };
  19     FIELD1
  20 }
  21
  22 const fn read_field2() -> Field2 {
  23     const FIELD2: Field2 = unsafe { UNION.field2 };
  24     FIELD2
  25 }
  26
  27 const fn read_field3() -> Field3 {
  28     const FIELD3: Field3 = unsafe { UNION.field3 };
  29     //~^ ERROR evaluation of constant value failed
  30     //~| uninitialized
  31     FIELD3
  32 }
  33
  34 fn main() {
  35     assert_eq!(read_field1(), FLOAT1_AS_I32);
  36     assert_eq!(read_field2(), 1.0);
  37     assert_eq!(read_field3(), unsafe { UNION.field3 });
  38 }