#![feature(rustc_attrs)] #[rustc_builtin_macro] macro_rules! option_env { () => {} } #[lang = "sized"] trait Sized {} pub mod core { pub mod option { pub enum Option { #[lang = "Some"] Some(T), #[lang = "None"] None, } } } use core::option::Option; fn main() { let _: Option<&str> = option_env!(42); // { dg-error "argument must be a string literal" "" { target *-*-* } .-1 } }