$ cargo run
   Compiling collections v0.1.0 (file:///projects/collections)
error[E0277]: the type `String` cannot be indexed by `{integer}`
 --> src/main.rs:3:13
  |
3 |     let h = s1[0];
  |             ^^^^^ `String` cannot be indexed by `{integer}`
  |
  = help: the trait `Index<{integer}>` is not implemented for `String`
  = help: the following other types implement trait `Index<Idx>`:
            <String as Index<RangeFrom<usize>>>
            <String as Index<RangeFull>>
            <String as Index<RangeInclusive<usize>>>
            <String as Index<RangeTo<usize>>>
            <String as Index<RangeToInclusive<usize>>>
            <String as Index<std::ops::Range<usize>>>

For more information about this error, try `rustc --explain E0277`.
error: could not compile `collections` due to previous error