78 lines
1.5 KiB
Rust
78 lines
1.5 KiB
Rust
//@ check-pass
|
|
|
|
use std::cell::RefMut;
|
|
|
|
fn main() {
|
|
StateMachine2::Init.resume();
|
|
}
|
|
|
|
enum StateMachine2<'a> {
|
|
Init,
|
|
#[allow(dead_code)] // match required for ICE
|
|
AfterTwoYields {
|
|
p: Backed<'a, *mut String>,
|
|
},
|
|
}
|
|
|
|
impl<'a> StateMachine2<'a> {
|
|
fn take(&self) -> Self {
|
|
StateMachine2::Init
|
|
}
|
|
}
|
|
|
|
impl<'a> StateMachine2<'a> {
|
|
fn resume(&mut self) -> () {
|
|
use StateMachine2::*;
|
|
match self.take() {
|
|
AfterTwoYields { p } => {
|
|
p.with(|_| {});
|
|
}
|
|
_ => panic!("Resume after completed."),
|
|
}
|
|
}
|
|
}
|
|
|
|
unsafe trait Unpack<'a> {
|
|
type Unpacked: 'a;
|
|
|
|
fn unpack(&self) -> Self::Unpacked {
|
|
unsafe { std::mem::transmute_copy(&self) }
|
|
}
|
|
}
|
|
|
|
unsafe trait Pack {
|
|
type Packed;
|
|
|
|
fn pack(&self) -> Self::Packed {
|
|
unsafe { std::mem::transmute_copy(&self) }
|
|
}
|
|
}
|
|
|
|
unsafe impl<'a> Unpack<'a> for String {
|
|
type Unpacked = String;
|
|
}
|
|
|
|
unsafe impl Pack for String {
|
|
type Packed = String;
|
|
}
|
|
|
|
unsafe impl<'a> Unpack<'a> for *mut String {
|
|
type Unpacked = &'a mut String;
|
|
}
|
|
|
|
unsafe impl<'a> Pack for &'a mut String {
|
|
type Packed = *mut String;
|
|
}
|
|
|
|
struct Backed<'a, U>(RefMut<'a, Option<String>>, U);
|
|
|
|
impl<'a, 'b, U: Unpack<'b>> Backed<'a, U> {
|
|
fn with<F>(self, f: F) -> Backed<'a, ()>
|
|
where
|
|
F: for<'f> FnOnce(<U as Unpack<'f>>::Unpacked) -> (),
|
|
{
|
|
let result: () = f(self.1.unpack());
|
|
Backed(self.0, result)
|
|
}
|
|
}
|