tests/ui/macros/empty-trailing-stmt.rs - third_party/github.com/rust-lang/rust - Git at Google

 macro_rules! empty {
     () => { }
 }

 fn foo() -> bool { //~ ERROR mismatched
     { true } //~ ERROR mismatched
     empty!();
 }

 fn main() {}
	macro_rules! empty {
	() => { }
	}

	fn foo() -> bool { //~ ERROR mismatched
	{ true } //~ ERROR mismatched
	empty!();
	}

	fn main() {}