Use-after-free when calling a derive more than once

[8BitMate]

I get a use-after-free error when calling the same derive macro more than once. It seems to be related to this issue. I didn't notice this problem in any of the tests, as it only happens when making a procedural macro. It seems the issue has to with using std::thread::LocalKey.

The issue may be resolved by removing the cashing inside the library! macro. However, I'm not entirely sure how we can remove the cashing of the Parent structs without making things incorrect.

Alternatively, it may be possible to replace all the occurrences of Ident inside the crate defined types, as the issue may be related to storing Span information between two calls to the same derive macro.