error: a macro named `foo` has already been exported
  --> $DIR/issue-38715.rs:5:1
   |
LL | macro_rules! foo { () => {} }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `foo` already exported
   |
note: previous macro export is now shadowed
  --> $DIR/issue-38715.rs:2:1
   |
LL | macro_rules! foo { ($i:ident) => {} }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to previous error