error[E0277]: the type `[{integer}]` cannot be indexed by `i32`
  --> $DIR/index-help.rs:3:7
   |
LL |     x[0i32];
   |       ^^^^ slice indices are of type `usize` or ranges of `usize`
   |
   = help: the trait `SliceIndex<[{integer}]>` is not implemented for `i32`
           but it is implemented for `usize`
   = help: for that trait implementation, expected `usize`, found `i32`
   = note: required for `Vec<{integer}>` to implement `Index<i32>`

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0277`.