error[E0384]: cannot assign twice to immutable variable `x` --> $DIR/command-line-diagnostics.rs:6:5 | LL | let x = 42; | - first assignment to `x` LL | x = 43; | ^^^^^^ cannot assign twice to immutable variable | help: consider making this binding mutable | LL | let mut x = 42; | +++ error: aborting due to 1 previous error For more information about this error, try `rustc --explain E0384`.