error[E0381]: used binding `x` isn't initialized
  --> $DIR/borrowck-break-uninit.rs:9:20
   |
LL |     let x: isize;
   |         - binding declared here but left uninitialized
...
LL |     println!("{}", x);
   |                    ^ `x` used here but it isn't initialized
   |
   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
help: consider assigning a value
   |
LL |     let x: isize = 0;
   |                  +++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0381`.