error[E0658]: The attribute `my_attr` is currently unknown to the compiler and may have meaning added to it in the future
  --> $DIR/derive-helper-shadowing.rs:20:15
   |
LL |             #[my_attr]
   |               ^^^^^^^
   |
   = note: for more information, see https://github.com/rust-lang/rust/issues/29642
   = help: add #![feature(custom_attribute)] to the crate attributes to enable

error[E0659]: `my_attr` is ambiguous (derive helper attribute vs any other name)
  --> $DIR/derive-helper-shadowing.rs:6:3
   |
LL | #[my_attr]
   |   ^^^^^^^ ambiguous name
   |
note: `my_attr` could refer to the derive helper attribute defined here
  --> $DIR/derive-helper-shadowing.rs:7:10
   |
LL | #[derive(MyTrait)]
   |          ^^^^^^^
note: `my_attr` could also refer to the attribute macro imported here
  --> $DIR/derive-helper-shadowing.rs:4:5
   |
LL | use derive_helper_shadowing::*;
   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
   = help: use `crate::my_attr` to refer to this attribute macro unambiguously

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0658, E0659.
For more information about an error, try `rustc --explain E0658`.