Compatibility with Rust 2018 paths

[jimmycuadra]

I'm trying to update ruma-events to Rust 2018 and the code generated by serde_derive seems to be using old-style paths that are resulting in compiler errors.

My crate has code like this (snippet from inside a decl macro expansion):

        #[derive(Clone, Debug, serde_derive::Deserialize, serde_derive::Serialize)]
        pub struct $name {
            /// The event's content.
            pub content: $content_type,

            /// The type of the event.
            #[serde(rename="type")]
            pub event_type: $crate::EventType,

But compiling results in errors like this:

error[E0412]: cannot find type `EventType` in the crate root
  --> src/macros.rs:81:32
   |
81 |         #[derive(Clone, Debug, serde_derive::Deserialize, serde_derive::Serialize)]
   |                                ^^^^^^^^^^^^^^^^^^^^^^^^^ not found in the crate root
help: possible candidate is found in another module, you can import it into scope
   |
3  | use crate::EventType;
   |

I see this in the output of cargo expand:

                            let __field2 = match match _serde::de::SeqAccess::next_element::<
                                ::EventType,
                            >(&mut __seq)

My understanding is that this should be:

                            let __field2 = match match _serde::de::SeqAccess::next_element::<
                                crate::EventType,
                            >(&mut __seq)

Is this something that needs to be fixed within serde or is there something I'm doing wrong here?

I'm using rustc 1.32.0-nightly (14997d56a 2018-12-05), serde v1.0.81, serde_derive v1.0.81.

Thanks!

[dtolnay]

Thanks! Closing in favor of a compiler issue because I believe serde_derive is doing it correctly: rust-lang/rust#56622.