Performance Issue on Large enums

[anlumo]

#[derive(TryFromPrimitive)]

takes about two minutes on my machine for an enum with ~6700 entries on every compile (even when the module it's in hasn't changed).

With RUSTFLAGS="-Ztime" set, the log output shows that the time is spent in the expand crate step.

[illicitonion]

This has since been fixed in one of our upstream dependencies (proc-macro2).

I've just published 0.4.2 of num_enum which should use that dependency - if you cargo update you should start seeing much better performance :)

Thanks for the bug report, it was an interesting one to dive into, and see others dive into as well, and the fix should hopefully help the wider rust ecosystem!