error[E0423]: expected function, found macro `println`
  --> $DIR/rustc-error.rs:LL:CC
   |
LL |     println("Hello, world!");
   |     ^^^^^^^ not a function
   |
help: use `!` to invoke the macro
   |
LL |     println!("Hello, world!");
   |            +

error: aborting due to previous error

For more information about this error, try `rustc --explain E0423`.