Currently, rustc does not pass the exact original TokenStream to
proc-macros in several cases. This has many undesirable effects, such as
losing correct location information in error message.
See rust-lang/rust#43081 for more details
In the future, rustc will begin passing the correct TokenStream to
proc-macros. As a result, `syn` may wrap a type in one or more
`syn::Type::Group`s (if the proc-macro input came from a `macro_rules!` expansion).
I've determined that this can cause `yaserde-derive` to fail to match
a `Type::Path`. This PR should properly handle nested groups, allowing
your crate to work with both old and new input.
If you have any questions, feel free to ask me. See rust-lang/rust#72622
for more details.
