serde_derive fails in latest nightly

[lambda-fairy]

Using this code:

#![feature(proc_macro)]

extern crate serde;
#[macro_use]
extern crate serde_derive;

#[derive(Deserialize)]
pub struct Foo;

fails with this error:

error[E0428]: a type named `Foo` has already been defined in this module
 --> src/lib.rs:8:1
  |
7 | #[derive(Deserialize)]
  |          ----------- previous definition of `Foo` here
8 | pub struct Foo;
  | ^^^^^^^^^^^^^^^ already defined

I am using rustc 1.15.0-nightly (43006fcea 2016-11-15) on Arch Linux.

[lambda-fairy]

Running rustc with --pretty=expanded yields the following:

#![feature(prelude_import)]
#![no_std]
#![feature(proc_macro)]
#[prelude_import]
use std::prelude::v1::*;
#[macro_use]
extern crate std as std;

extern crate serde;
#[macro_use]
extern crate serde_derive;

pub struct Foo;
#[allow(non_upper_case_globals, unused_attributes, unused_qualifications)]
const _IMPL_DESERIALIZE_FOR_Foo: () =
    {
        extern crate serde as _serde;
        #[automatically_derived]
        impl _serde::de::Deserialize for Foo {
            fn deserialize<__D>(deserializer: &mut __D)
             -> ::std::result::Result<Foo, __D::Error> where
             __D: _serde::de::Deserializer {
                struct __Visitor;
                impl _serde::de::Visitor for __Visitor {
                    type
                    Value
                    =
                    Foo;
                    #[inline]
                    fn visit_unit<__E>(&mut self)
                     -> ::std::result::Result<Foo, __E> where
                     __E: _serde::de::Error {
                        Ok(Foo)
                    }
                    #[inline]
                    fn visit_seq<__V>(&mut self, mut visitor: __V)
                     -> ::std::result::Result<Foo, __V::Error> where
                     __V: _serde::de::SeqVisitor {
                        match visitor.end() {
                            $crate::result::Result::Ok(val) => val,
                            $crate::result::Result::Err(err) => {
                                return $crate::result::Result::Err($crate::convert::From::from(err))
                            }
                        };
                        self.visit_unit()
                    }
                }
                deserializer.deserialize_unit_struct("Foo", __Visitor)
            }
        }
    };
pub struct Foo;

Note the duplicated pub struct Foo.

[lambda-fairy]

Duplicate of #614