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// 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)
}
}
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