error[E0381]: used binding `last_error` isn't initialized --> $DIR/issue-103250.rs:22:13 | LL | let mut last_error: Box; | -------------- binding declared here but left uninitialized ... LL | Err(last_error) | ^^^^^^^^^^ `last_error` used here but it isn't initialized | help: consider assigning a value | LL | let mut last_error: Box = todo!(); | +++++++++ error: aborting due to previous error For more information about this error, try `rustc --explain E0381`.