Generic key type prevents finding with non-static slices

[chris-morgan]

PhfMap<&'static str, Keyword> has K set to &'static str. This is an absolute killer for rust-phf, negating (without unsafe code) the whole point of the library.

fn find<'a>(&'a self, key: &K) -> Option<&'a V>

In other words, this is

fn find<'a>(&'a self, key: &&'static str) -> Option<&'a Keyword>

See the problem? I must pass the key as a reference to a static string.

If I wanted to do it based on user input—by far the most common case, I expect—I cannot do that, for it is not &'static str.

As it stands, I must cheat by transmuting the lifetime for the duration of the call, knowing it to be safe.

We evidently need something else. Straight generics don’t cut it.

[sfackler]

find_equiv exists to work around this problem.

[sfackler]

But I agree it is an issue.

[chris-morgan]

I had assumed that find_equiv was going to be inefficient. Am I wrong in that assumption?

[sfackler]

find_equiv has exactly the same performance characteristics as find. It just changes the final equality check from a == b to a.equiv(b).

[chris-morgan]

(I was unaware of the unwritten assumption that Equiv means the same hash also—this assumption is what allows it to be just as efficient, but it scares me significantly!)

[sfackler]

It is a bit dubious, but it's consistent with the way it's used in HashMap. I think @aturon is working on/thinking about a better solution.