error[E0015]: `?` is not allowed on `Option<i32>` in constant functions
  --> $DIR/try.rs:6:5
   |
LL |     x?;
   |     ^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants

error[E0015]: `?` is not allowed on `Option<i32>` in constant functions
  --> $DIR/try.rs:6:5
   |
LL |     x?;
   |     ^^
   |
   = note: calls in constant functions are limited to constant functions, tuple structs and tuple variants

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0015`.