I am attempting to try out Rocket web framework with a very small example. However, Rocket (0.4.2) wont compile with the nightly rustc. (Using Ubuntu linux.) 

I am building using nightly rustc (2019-09-05). Just did a rustup to try the latest rustc. I am using these versions:

* nightly-x86\_64-unknown-linux-gnu (directory override for '/work/cd/rusty/cdbackend')
* rustc 1.39.0-nightly (618768492 2019-09-05)
* Rocket 0.4.2

I get the following error:

```
error: /work/cd/rusty/cdbackend/target/debug/deps/librocket_codegen-33108ba93258cfa7.so: undefined symbol: __rustc_plugin_registrar_a555dc3e7aee69391ac43d72ccd8fe72__
 --> src/main.rs:2:11
  |
2 | #![plugin(rocket_codegen)]
  |           ^^^^^^^^^^^^^^

error: aborting due to previous error

```

Any ideas on what version will compile?