src/test/ui/feature-gate/rustc-private.stderr

   1 error[E0658]: use of unstable library feature 'rustc_private': this crate is being loaded from the sysroot, an unstable location; did you mean to load this crate from crates.io via `Cargo.toml` instead?
   2   --> $DIR/rustc-private.rs:3:1
   3    |
   4 LL | extern crate libc;
   5    | ^^^^^^^^^^^^^^^^^^
   6    |
   7    = note: see issue #27812 <https://github.com/rust-lang/rust/issues/27812> for more information
   8    = help: add `#![feature(rustc_private)]` to the crate attributes to enable
   9
  10 error: aborting due to previous error
  11
  12 For more information about this error, try `rustc --explain E0658`.