warning: `try` is a keyword in the 2018 edition
  --> $DIR/lint_pre_expansion_extern_module_aux.rs:3:8
   |
LL | pub fn try() {}
   |        ^^^ help: you can use a raw identifier to stay compatible: `r#try`
   |
   = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018!
   = note: for more information, see issue #49716 <https://github.com/rust-lang/rust/issues/49716>
   = note: `-W keyword-idents-2018` implied by `-W rust-2018-compatibility`
   = help: to override `-W rust-2018-compatibility` add `#[allow(keyword_idents_2018)]`

warning: 1 warning emitted