Racerd fails on unstable

[NorfairKing]

Describe the bug
A clear and concise description of what the bug is.

racerd fails to build on the latest unstable nixpkgs:

error[E0061]: this function takes 1 argument but 0 arguments were supplied
  --> /build/racerd-unstable-2019-09-02-vendor.tar.gz/rustc-ap-rustc_data_structures/box_region.rs:36:58
   |
36 |         let init = match Pin::new(&mut result.generator).resume() {
   |                                                          ^^^^^^- supplied 0 arguments
   |
help: expected the unit value `()`; create it with empty parentheses
   |
36 |         let init = match Pin::new(&mut result.generator).resume(()) {
   |                                                                 ^^

error[E0061]: this function takes 1 argument but 0 arguments were supplied
  --> /build/racerd-unstable-2019-09-02-vendor.tar.gz/rustc-ap-rustc_data_structures/box_region.rs:52:76
   |
52 |         if let GeneratorState::Complete(_) = Pin::new(&mut self.generator).resume() {
   |                                                                            ^^^^^^- supplied 0 arguments
   |
help: expected the unit value `()`; create it with empty parentheses
   |
52 |         if let GeneratorState::Complete(_) = Pin::new(&mut self.generator).resume(()) {
   |                                                                                   ^^

error[E0061]: this function takes 1 argument but 0 arguments were supplied
  --> /build/racerd-unstable-2019-09-02-vendor.tar.gz/rustc-ap-rustc_data_structures/box_region.rs:63:52
   |
63 |         let result = Pin::new(&mut self.generator).resume();
   |                                                    ^^^^^^- supplied 0 arguments
   |
help: expected the unit value `()`; create it with empty parentheses
   |
63 |         let result = Pin::new(&mut self.generator).resume(());
   |                                                           ^^

   Compiling persistent v0.4.0
   Compiling router v0.6.0
error: aborting due to 3 previous errors

For more information about this error, try `rustc --explain E0061`.
error: could not compile `rustc-ap-rustc_data_structures`.

To learn more, run the command again with --verbose.
warning: build failed, waiting for other jobs to finish...
error: build failed
builder for '/nix/store/c34jf7iy6dr4i8j6r35sl1550yq192m4-racerd-unstable-2019-09-02.drv' failed with exit code 101
cannot build derivation '/nix/store/74ppcvm04xvgvsxi17bayncp3qq35r4z-ycmd-2020-02-22.drv': 1 dependencies couldn't be built
cannot build derivation '/nix/store/clhky8y6ghwkiyi8xbbsxa54lkbiajqn-vimplugin-YouCompleteMe-2020-05-25.drv': 1 dependencies couldn't be built

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Metadata
Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

 - system: `"x86_64-linux"`
 - host os: `Linux 5.4.35, NixOS, 20.09pre227577.135073a87b7 (Nightingale)`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.3.5`
 - channels(root): `"nixos-20.09pre228622.029a5de0839"`
 - channels(syd): `""`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[luc65r]

Kind of a duplicate of #89481.
It needs Nightly Rust.

[NorfairKing]

Jup, seems like it!