error[E0658]: non-builtin inner attributes are unstable
  --> $DIR/issue-36530.rs:9:5
   |
LL |     #![foo]
   |     ^^^^^^^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/54726
   = help: add `#![feature(custom_inner_attributes)]` to the crate attributes to enable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.