error: a macro named `foo` has already been exported
  --> $DIR/issue-38715.rs:15:1
   |
LL | macro_rules! foo { () => {} } //~ ERROR a macro named `foo` has already been exported
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ `foo` already exported
   |
   = note: #[deny(duplicate_macro_exports)] on by default
   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in the 2018 edition!
   = note: for more information, see issue #35896 <https://github.com/rust-lang/rust/issues/35896>
note: previous macro export is now shadowed
  --> $DIR/issue-38715.rs:12:1
   |
LL | macro_rules! foo { ($i:ident) => {} }
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0601]: `main` function not found in crate `issue_38715`
   |
   = note: consider adding a `main` function to `$DIR/issue-38715.rs`

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0601`.