error: expected one of `!` or `::`, found `foo`
  --> $DIR/fn-defined-using-function.rs:6:10
   |
LL | function foo() {}
   | -------- ^^^ expected one of `!` or `::`
   | |
   | help: write `fn` instead of `function` to declare a function

error: aborting due to 1 previous error