error[E0019]: constant contains unimplemented expression type
  --> $DIR/infinite_loop.rs:19:9
   |
LL | /         while n != 0 { //~ ERROR constant contains unimplemented expression type
LL | |             n = if n % 2 == 0 { n/2 } else { 3*n + 1 };
LL | |             //~^ ERROR evaluation of constant value failed
LL | |         }
   | |_________^

warning: Constant evaluating a complex constant, this might take some time
  --> $DIR/infinite_loop.rs:16:18
   |
LL |       let _ = [(); {
   |  __________________^
LL | |         //~^ WARNING Constant evaluating a complex constant, this might take some time
LL | |         let mut n = 113383; // #20 in https://oeis.org/A006884
LL | |         while n != 0 { //~ ERROR constant contains unimplemented expression type
...  |
LL | |         n
LL | |     }];
   | |_____^

error[E0080]: evaluation of constant value failed
  --> $DIR/infinite_loop.rs:20:20
   |
LL |             n = if n % 2 == 0 { n/2 } else { 3*n + 1 };
   |                    ^^^^^^^^^^ duplicate interpreter state observed here, const evaluation will never terminate

error: aborting due to 2 previous errors

Some errors occurred: E0019, E0080.
For more information about an error, try `rustc --explain E0019`.