[rust-dev] Patterns that'll never match

Corey Richardson corey at octayn.net
Sun Jun 1 01:40:35 PDT 2014


We already *do* do this, but not for guards because that's not possible.

On Sun, Jun 1, 2014 at 12:02 AM, Tommi <rusty.gates at icloud.com> wrote:
> Would it be possible to get a compile-time error for a `match` branch that can never be reached due to a previous branch encompassing it. For example, for the middle branch here:
>
> let n = 0;
> match n {
>     x if x < 2 => (),
>     x if x < 1 => (),
>     _ => ()
> }
>
> If this is a too complicated a problem in the general case, then perhaps there could be warnings for some (implementation defined) simple cases.
>
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