    proc_macros::mirror! {
        {
            ,i32 :x pub
            ,i32 :y pub
        } Foo struct
    }
    macro_rules! def_fn {
        ($($tt:tt)*) => {$($tt)*}
    }

    def_fn! {
        fn bar() -> u32 {
            100
        }
    }

    macro_rules! dont_color_me_braces {
        () => {0}
    }

    macro_rules! noop {
        ($expr:expr) => {
            $expr
        }
    }

    /// textually shadow previous definition
    macro_rules! noop {
        ($expr:expr) => {
            $expr
        }
    }

    macro_rules! keyword_frag {
        ($type:ty) => ($type)
    }

    macro with_args($i:ident) {
        $i
    }

    macro without_args {
        ($i:ident) => {
            $i
        }
    }

    #[rustc_builtin_macro]
    macro_rules! concat {}
    #[rustc_builtin_macro]
    macro_rules! include {}
    #[rustc_builtin_macro]
    macro_rules! format_args {}

    include!(concat!("foo/", "foo.rs"));

    fn main() {
        format_args!("Hello, {}!", 92);
        dont_color_me_braces!();
        noop!(noop!(1));
    }