error: `macro_use` attributes are no longer needed in the Rust 2018 edition
  --> $DIR/macro_use_imports.rs:5:1
   |
LL | #[macro_use]
   | ^^^^^^^^^^^^ help: remove the attribute and import the macro directly, try: `use std::prelude::<macro name>`
   |
   = note: `-D clippy::macro-use-imports` implied by `-D warnings`

error: aborting due to previous error