//! lib-proc-macro Closure type (equivalent to `&mut dyn FnMut(A) -> R`) that's `repr(C)`. //! //! Copy from https://github.com/rust-lang/rust/blob/6050e523bae6de61de4e060facc43dc512adaccd/src/libproc_macro/bridge/closure.rs# //! augmented with removing unstable features #[repr(C)] pub struct Closure<'a, A, R> { call: unsafe extern "C" fn(&mut Env, A) -> R, env: &'a mut Env, } struct Env; // impl<'a, A, R> !Sync for Closure<'a, A, R> {} // impl<'a, A, R> !Send for Closure<'a, A, R> {} impl<'a, A, R, F: FnMut(A) -> R> From<&'a mut F> for Closure<'a, A, R> { fn from(f: &'a mut F) -> Self { unsafe extern "C" fn call<A, R, F: FnMut(A) -> R>(env: &mut Env, arg: A) -> R { (*(env as *mut _ as *mut F))(arg) } Closure { call: call::<A, R, F>, env: unsafe { &mut *(f as *mut _ as *mut Env) } } } } impl<'a, A, R> Closure<'a, A, R> { pub fn call(&mut self, arg: A) -> R { unsafe { (self.call)(self.env, arg) } } }