error[E0384]: cannot assign twice to immutable variable `nyan`
  --> $DIR/mutable-class-fields.rs:28:3
   |
LL |   let nyan : cat = cat(52, 99);
   |       ----
   |       |
   |       first assignment to `nyan`
   |       consider changing this to `mut nyan`
LL |   nyan.how_hungry = 0; //[ast]~ ERROR cannot assign
   |   ^^^^^^^^^^^^^^^^^^^ cannot assign twice to immutable variable

error: aborting due to previous error

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