with_locals 0.3.3

#![forbid(unsafe_code)]

#[macro_use]
extern crate with_locals;

use ::core::fmt::Display;

#[test]
#[with('local)]
fn hex ()
{
    #[with('local)]
    fn hex (n: u32) -> &'local dyn Display
    {
        &format_args!("{:#x}", n)
    }

    #[with]
    let s_hex = hex(66);
    assert_eq!(s_hex.to_string(), "0x42");
}

mod to_str {
    trait ToStr {
        #[with('local)]
        fn to_str (self: &'_ Self) -> &'local str
        ;
    }

    impl ToStr for u32 {
        #[with('local)]
        fn to_str (self: &'_ u32) -> &'local str
        {
            let mut x = *self;
            if x == 0 { return "0"; }
            let mut buf = [b' '; 1 + 3 + 3 + 3]; // u32::MAX ~ 4_000_000_000
            let mut cursor = &mut buf[..];
            while x > 0 {
                let (last, cursor_) = cursor.split_last_mut().unwrap();
                cursor = cursor_;
                *last = b'0' + (x % 10) as u8;
                x /= 10;
            }
            let len = cursor.len();
            ::core::str::from_utf8(&buf[len ..])
                .unwrap()
        }
    }

    #[test]
    #[with('local)]
    fn basic ()
    {

        #[with]
        let n: &str = ::core::u32::MAX.to_str();
        dbg!(n);
        assert_eq!(n.parse(), Ok(::core::u32::MAX));
    }

    #[test]
    #[with('local)]
    fn romans ()
    {

        struct Roman(u8); impl ToStr for Roman {
            #[with('local)]
            fn to_str (self: &'_ Self) -> &'local str
            {
                let mut buf = [b' '; 1 + 4 + 4];  // C LXXX VIII or CC XXX VIII
                let mut start = buf.len();
                let mut prepend = |b| {
                    start = start.checked_sub(1).unwrap();
                    buf[start] = b;
                };
                let mut n = self.0;
                if n == 0 {
                    panic!("Vade retro!");
                }
                const DIGITS: [u8; 7] = *b"IVXLCDM";
                (0 ..= 2).for_each(|shift| {
                    #[allow(nonstandard_style)]
                    let (I, V, X) = (
                        DIGITS[2 * shift],
                        DIGITS[2 * shift + 1],
                        DIGITS[2 * shift + 2],
                    );
                    match n % 10 {
                        | units @ 0 ..= 3 => {
                            (0 .. units).for_each(|_| prepend(I));
                        },
                        | 4 => {
                            prepend(V);
                            prepend(I);
                        },
                        | units @ 5 ..= 8 => {
                            (0 .. units - 5).for_each(|_| prepend(I));
                            prepend(V);
                        },
                        | 9 => {
                            prepend(X);
                            prepend(I);
                        },
                        | _ => unreachable!(),
                    }
                    n /= 10;
                });
                return ::core::str::from_utf8(&buf[start ..]).unwrap();
            }
        }

        let ref mut out = String::new();
        for n in 1 ..= ::core::u8::MAX {
            use ::core::fmt::Write;

            #[with]
            let roman = Roman(n).to_str();
            writeln!(out, "{:3} = {}", n, roman).unwrap();
        }
        assert_eq!(
            out.as_str(),
            include_str!("romans.txt")
                .replace("\r\n", "\n")
                .as_str()
            ,
        );
    }
}

#[test]
#[with('local)]
fn loops ()
{
    use ::core::cell::RefCell;

    trait Iterable {
        #[with('local)]
        fn next (self: &'_ mut Self)
          -> Option<&'local i32>
        ;
    }

    fn iter_refcells (refcells: &'_ [RefCell<i32>])
      -> impl '_ + Iterable
    {
        return Ret(refcells.iter());
        // where
        struct Ret<'__> (::core::slice::Iter<'__, RefCell<i32>>);
        impl Iterable for Ret<'_> {
            #[with('local)]
            fn next (self: &'_ mut Self)
              -> Option<&'local i32>
            {
                Some(&*self.0.next()?.borrow())
            }
        }
    }

    let ref elems = [
        RefCell::new(0),
        RefCell::new(1),
        RefCell::new(2),
        RefCell::new(3),
    ];

    let mut iterable = iter_refcells(elems);
    let mut acc = vec![];
    loop {
        #[with]
        let next = iterable.next();
        if let Some(&item) = next {
            if item == 1 { continue; }
            acc.push(item)
        } else {
            break;
        }
    }
    assert_eq!(
        acc,
        [0, 2, 3],
    );
    /* The above loop unsugared to:
    ```rust
    loop {
        match iterable.with_next(|next| {
            ::with_locals::__::ControlFlow::<
                _,
                ::with_locals::__::Unreachable,
                ::with_locals::__::Unreachable,
                _,
                (),
            >::Eval({
                if let Some(&item) = next {
                    if item == 1 {
                        return ::with_locals::__::ControlFlow::Continue(());
                    }
                    acc.push(item)
                } else {
                    return ::with_locals::__::ControlFlow::Break(());
                }
            })
        }) {
            ::with_locals::__::ControlFlow::Eval(it) => it,
            ::with_locals::__::ControlFlow::EarlyReturn(it) => {
                let unreachable = it;
                match unreachable {}
            }
            ::with_locals::__::ControlFlow::PropagateError(it) => {
                let unreachable = it;
                match unreachable {}
            }
            ::with_locals::__::ControlFlow::Break(it) => break it,
            ::with_locals::__::ControlFlow::Continue(it) => {
                let () = it;
                continue;
            }
        }
    }
    ```
    */
}

#[test]
#[with('local)]
fn recursive ()
{
    /// Recursive
    #[with('local, recursive = true)]
    fn recursive_f (recurse: bool) -> &'local ()
    {
        if recurse {
            let _: &'local _ = recursive_f(false);
        }
        &()
    }
    let _it: &'local () = recursive_f(true);
}

#[test]
#[with('local)]
fn object_safe ()
{
    #[with('local, dyn_safe = true)]
    trait DynSafe {
        fn foo (&self) -> &'local ()
        {
            &()
        }
    }
    impl DynSafe for () {}
    let dyn_obj: &'_ dyn DynSafe = &();
    #[with(dyn_safe)]
    let _: &'local () = dyn_obj.foo();
    return;
}