error[E0608]: cannot index into a value of type `()`
  --> $DIR/index_message.rs:13:13
   |
LL |     let _ = z[0]; //~ ERROR cannot index into a value of type `()`
   |             ^^^^ help: to access tuple elements, use: `z.0`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0608`.