error: unused macro definition: `a`
  --> $DIR/concat-in-crate-name-issue-137687.rs:5:14
   |
LL | macro_rules! a {
   |              ^
   |
note: the lint level is defined here
  --> $DIR/concat-in-crate-name-issue-137687.rs:1:9
   |
LL | #![deny(unused)]
   |         ^^^^^^
   = note: `#[deny(unused_macros)]` implied by `#[deny(unused)]`

error: crate-level attribute should be an inner attribute: add an exclamation mark: `#![crate_name]`
  --> $DIR/concat-in-crate-name-issue-137687.rs:3:1
   |
LL | #[crate_name = concat !()]
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
note: This attribute does not have an `!`, which means it is applied to this macro def
  --> $DIR/concat-in-crate-name-issue-137687.rs:5:1
   |
LL | / macro_rules! a {
LL | |
LL | |     () => {};
LL | | }
   | |_^
   = note: `#[deny(unused_attributes)]` implied by `#[deny(unused)]`

error: aborting due to 2 previous errors