error[E0384]: cannot assign twice to immutable variable `b`
  --> $DIR/liveness-assign-imm-local-with-drop.rs:6:5
   |
LL |     let b = Box::new(1);
   |         - first assignment to `b`
...
LL |     b = Box::new(2);
   |     ^ cannot assign twice to immutable variable
   |
help: consider making this binding mutable
   |
LL |     let mut b = Box::new(1);
   |         +++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0384`.