// `/**/` was previously regarded as a doc comment because it starts with `/**` and ends with `*/`. // This could break some internal logic that assumes the length of a doc comment is at least 5, // leading to an ICE. macro_rules! one_arg_macro { ($fmt:expr) => (print!(concat!($fmt, "\n"))); } fn main() { one_arg_macro!(/**/); //~ ERROR unexpected end }