error[E0384]: cannot assign twice to immutable variable `v`
  --> $DIR/assign-imm-local-twice.rs:7:5
   |
LL |     let v: isize;
   |         - help: consider making this binding mutable: `mut v`
...
LL |     v = 1;
   |     ----- first assignment to `v`
LL |     println!("v={}", v);
LL |     v = 2;
   |     ^^^^^ cannot assign twice to immutable variable

error: aborting due to previous error

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