// { dg-additional-options "-frust-name-resolution-2.0 -frust-compile-until=lowering" }

macro_rules! impl_fn_for_zst {
    ($(
        $( #[$attr: meta] )*
        struct $Name: ident impl$( <$( $lifetime : lifetime ),+> )? Fn =
            |$( $arg: ident: $ArgTy: ty ),*| -> $ReturnTy: ty
            $body: block;
    )+) => {
        $(
            $( #[$attr] )*
            struct $Name;

            impl $( <$( $lifetime ),+> )? Fn<($( $ArgTy, )*)> for $Name {
                #[inline]
                extern "rust-call" fn call(&self, ($( $arg, )*): ($( $ArgTy, )*)) -> $ReturnTy {
                    $body
                }
            }

            impl $( <$( $lifetime ),+> )? FnMut<($( $ArgTy, )*)> for $Name {
                #[inline]
                extern "rust-call" fn call_mut(
                    &mut self,
                    ($( $arg, )*): ($( $ArgTy, )*)
                ) -> $ReturnTy {
                    Fn::call(&*self, ($( $arg, )*))
                }
            }

            impl $( <$( $lifetime ),+> )? FnOnce<($( $ArgTy, )*)> for $Name {
                type Output = $ReturnTy;

                #[inline]
                extern "rust-call" fn call_once(self, ($( $arg, )*): ($( $ArgTy, )*)) -> $ReturnTy {
                    Fn::call(&self, ($( $arg, )*))
                }
            }
        )+
    }
}

#[lang = "sized"]
trait Sized {}

#[lang = "copy"]
trait Copy {}

#[lang = "fn"]
pub trait Fn<Args>: FnMut<Args> {
    /// Performs the call operation.
    #[unstable(feature = "fn_traits", issue = "29625")]
    extern "rust-call" fn call(&self, args: Args) -> Self::Output;
}

#[lang = "fn_mut"]
#[must_use = "closures are lazy and do nothing unless called"]
pub trait FnMut<Args>: FnOnce<Args> {
    /// Performs the call operation.
    #[unstable(feature = "fn_traits", issue = "29625")]
    extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output;
}

#[lang = "fn_once"]
pub trait FnOnce<Args> {
    /// The returned type after the call operator is used.
    #[lang = "fn_once_output"]
    #[stable(feature = "fn_once_output", since = "1.12.0")]
    type Output;

    /// Performs the call operation.
    #[unstable(feature = "fn_traits", issue = "29625")]
    extern "rust-call" fn call_once(self, args: Args) -> Self::Output;
}

impl_fn_for_zst! {
    /// Documentation for the zst
    #[derive(Copy)]
    struct LinesAnyMap impl<'a> Fn = |line: &'a str| -> () {
    };
}