// This module needs the following features. // //#![feature(unboxed_closures)] //#![feature(fn_traits)] pub struct FnNOP(); impl Fn<()> for FnNOP { extern "rust-call" fn call(&self, _args: ()) {} } impl FnMut<()> for FnNOP { extern "rust-call" fn call_mut(&mut self, _args: ()) {} } impl FnOnce<()> for FnNOP { type Output = (); extern "rust-call" fn call_once(self, _args: ()) {} } static mut NOP: FnNOP = FnNOP();