Missing ```AltPattern``` typechecking

[powerboat9]

I tried this code:

pub fn main() {
    match 12 {
        12 | 13 | 14 => {}
        _ => {}
    }
}

I expected to see this happen: no error

Instead, this happened:

<source>:3:9: sorry, unimplemented: type checking alternate patterns not supported
    3 |         12 | 13 | 14 => {}
      |         ^~