tests/ui/root_namespace.rs - platform/external/rust/cxx - Git at Google

 #[cxx::bridge]
 mod ffi {
     #[namespace = "::"]
     extern "Rust" {}

     #[namespace = ""]
     extern "Rust" {}

     #[namespace = ]
     extern "Rust" {}
 }

 fn main() {}
	#[cxx::bridge]
	mod ffi {
	#[namespace = "::"]
	extern "Rust" {}

	#[namespace = ""]
	extern "Rust" {}

	#[namespace = ]
	extern "Rust" {}
	}

	fn main() {}