Proc macro gives bad error about custom derives if regular macro with the same name is imported first

[Arnavion]

rustc 1.16.0-nightly (7821a9b 2017-01-23)

main.rs

#[macro_use] extern crate derive_error_chain;
#[macro_use] extern crate error_chain;

#[derive(Debug, error_chain)]
pub enum ErrorKind {
    Msg(String),
}

fn main() {
}

Cargo.toml

[package]
name = "rust-test"
version = "0.1.0"
authors = ["Arnavion <[email protected]>"]

[dependencies]
derive-error-chain = "=0.8.0"
error-chain = "=0.8.1"

cargo build gives:

error: `#[derive]` for custom traits is not stable enough for use. It is deprecated and will be removed in v1.15 (see issue #29644)
 --> src\main.rs:4:17
  |
4 | #[derive(Debug, error_chain)]
  |                 ^^^^^^^^^^^
  |
  = help: add #![feature(custom_derive)] to the crate attributes to enable

error: aborting due to previous error

derive-error-chain exports a proc macro named error_chain. error-chain exports a regular macro named error_chain.

Everything's fine if the order of the extern crate statements is reversed, or error-chain's import does not have #[macro_use].

[keeperofdakeys]

Unfortunately macro_rules, proc-macro derives, and future proc-macros share the same namespace. So I don't think there is a way to fix this besides renaming one of the macros.

@nrc ?

[Arnavion]

I'm not asking for a way to make this work. I'm asking for an error message that isn't misleading :)

[keeperofdakeys]

Ah, I'm actually working on a PR right now which should fix this, I'll be sure to keep it in mind #39391.