error: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
  --> $DIR/issue-36530.rs:11:1
   |
11 | #[foo] //~ ERROR is currently unknown to the compiler
   | ^^^^^^
   |
   = help: add #![feature(custom_attribute)] to the crate attributes to enable

error: The attribute `foo` is currently unknown to the compiler and may have meaning added to it in the future (see issue #29642)
  --> $DIR/issue-36530.rs:13:5
   |
13 |     #![foo] //~ ERROR is currently unknown to the compiler
   |     ^^^^^^^
   |
   = help: add #![feature(custom_attribute)] to the crate attributes to enable

error: aborting due to 2 previous errors