error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
  --> $DIR/issue-70971.rs:2:14
   |
LL |     let x : (impl Copy,) = (true,);
   |              ^^^^^^^^^
   |
   = note: found `impl Trait` in variable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0562`.