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