// Regression test for issue #27592. fn write<'a, F: ::std::ops::FnOnce()->::std::fmt::Arguments<'a> + 'a>(fcn: F) { use std::fmt::Write; let _ = match fcn() { a => write!(&mut Stream, "{}", a), }; } struct Stream; impl ::std::fmt::Write for Stream { fn write_str(&mut self, _s: &str) -> ::std::fmt::Result { Ok( () ) } } fn main() { write(|| format_args!("{}", String::from("Hello world"))); //~^ ERROR cannot return value referencing temporary value //~| ERROR cannot return reference to temporary value }