error: expected identifier, found keyword `fn`
  --> $DIR/keyword-fn-as-identifier.rs:4:9
   |
LL |     let fn = "foo";
   |         ^^ expected identifier, found keyword
   |
help: escape `fn` to use it as an identifier
   |
LL |     let r#fn = "foo";
   |         ++

error: aborting due to previous error