#![feature(pin)]

use std::pin::Pin;

macro_rules! pin_proj {
    (@record({}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        let &mut $st {$($p)*} = unsafe { Pin::get_mut_unchecked($e) };
        $(
            let $binders = unsafe { Pin::new_unchecked($binders) };
        )*
    };
    (@record({..}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({}, $st, $e, {$($p)* ..}, [$($binders)*]) }
    };
    (@record({$field:ident, $($rem:tt)*}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({$($rem)*}, $st, $e, {$($p)* ref mut $field,}, [$($binders)* $field]) }
    };
    (@record({$field:ident}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({}, $st, $e, {$($p)* ref mut $field}, [$($binders)* $field]) }
    };
    (@record({$field:ident : _, $($rem:tt)*}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({$($rem)*}, $st, $e, {$($p)* $field: _,}, [$($binders)*]) }
    };
    (@record({$field:ident : _}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({}, $st, $e, {$($p)* $field: _}, [$($binders)*]) }
    };
    (@record({$field:ident : $var:ident, $($rem:tt)*}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({$($rem)*}, $st, $e, {$($p)* $field: ref mut $var,}, [$($binders)* $var]) }
    };
    (@record({$field:ident : $var:ident}, $st:path, $e:expr, {$($p:tt)*}, [$($binders:ident)*])) => {
        pin_proj! { @record({}, $st, $e, {$($p)* $field: ref mut $var}, [$($binders)* $var]) }
    };
    (let $st:path {$($fields:tt)*} = $e:expr;) => {
        pin_proj! { @record({$($fields)*}, $st, $e, {}, []) }
    };
}

pub struct A {}

pub fn test1(x: Pin<&mut A>) {
    pin_proj! {
        let A {} = x;
    }
}

pub struct B {
    x: i32,
    y: i32,
}

pub fn test2(x: Pin<&mut B>) {
    pin_proj! {
        let B { x, y: z } = x;
    }
    fn foo(_: Pin<&mut i32>) {}
    foo(x);
    foo(z);
}