druid: druid-derive: syn::ty::Type` doesn't implement `std::fmt::Debug

I couldn’t get any Druid project to compile. Was getting some kind of linker error. I went through the crates one by one, attempting to find out where it was breaking.

If I put druid-derive = "0.3.1" into my Cargo.toml dependencies, and try to run nothing but an empty main(). This is the error I get:

   Compiling druid-derive v0.3.1
error[E0277]: `syn::ty::Type` doesn't implement `std::fmt::Debug`
  --> /home/arif/.cargo/registry/src/github.com-1ecc6299db9ec823/druid-derive-0.3.1/src/attr.rs:65:5
   |
65 |     pub ty: syn::Type,
   |     ^^^^^^^^^^^^^^^^^ `syn::ty::Type` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
   |
   = help: the trait `std::fmt::Debug` is not implemented for `syn::ty::Type`
   = note: required because of the requirements on the impl of `std::fmt::Debug` for `&syn::ty::Type`
   = note: required for the cast to the object type `dyn std::fmt::Debug`
   = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)

error[E0277]: `syn::expr::ExprPath` doesn't implement `std::fmt::Debug`
  --> /home/arif/.cargo/registry/src/github.com-1ecc6299db9ec823/druid-derive-0.3.1/src/attr.rs:69:5
   |
69 |     pub same_fn: Option<ExprPath>,
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `syn::expr::ExprPath` cannot be formatted using `{:?}` because it doesn't implement `std::fmt::Debug`
   |
   = help: the trait `std::fmt::Debug` is not implemented for `syn::expr::ExprPath`
   = note: required because of the requirements on the impl of `std::fmt::Debug` for `std::option::Option<syn::expr::ExprPath>`
   = note: required because of the requirements on the impl of `std::fmt::Debug` for `&std::option::Option<syn::expr::ExprPath>`
   = note: required for the cast to the object type `dyn std::fmt::Debug`
   = note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)