error[E0381]: used binding `x` isn't initialized --> $DIR/borrowck-uninit.rs:5:9 | LL | let x: isize; | - binding declared here but left uninitialized LL | foo(x); | ^ `x` used here but it isn't initialized | help: consider assigning a value | LL | let x: isize = 0; | +++ error: aborting due to previous error For more information about this error, try `rustc --explain E0381`.