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//! Implementation for `arr!` macro.↩
↩
use super::ArrayLength;↩
use core::ops::Add;↩
use typenum::U1;↩
↩
/// Helper trait for `arr!` macro↩
pub trait AddLength<T, N: ArrayLength<T>>: ArrayLength<T> {↩
/// Resulting length↩
type Output: ArrayLength<T>;↩
}↩
↩
impl<T, N1, N2> AddLength<T, N2> for N1↩
where↩
N1: ArrayLength<T> + Add<N2>,↩
N2: ArrayLength<T>,↩
<N1 as Add<N2>>::Output: ArrayLength<T>,↩
{↩
type Output = <N1 as Add<N2>>::Output;↩
}↩
↩
/// Helper type for `arr!` macro↩
pub type Inc<T, U> = <U as AddLength<T, U1>>::Output;↩
↩
#[doc(hidden)]↩
#[macro_export]↩
macro_rules! arr_impl {↩
(@replace_expr $e:expr) => { 1 };↩
($T:ty; $N:ty, [$($x:expr),*], []) => ({↩
const __ARR_LENGTH: usize = 0 $(+ $crate::arr_impl!(@replace_expr $x) )*;↩
↩
#[inline(always)]↩
fn __do_transmute<T, N: $crate::ArrayLength<T>>(arr: [T; __ARR_LENGTH]) -> $crate::GenericArray<T, N> {↩
unsafe { $crate::transmute(arr) }↩
}↩
↩
let _: [(); <$N as $crate::typenum::Unsigned>::USIZE] = [(); __ARR_LENGTH];↩
↩
__do_transmute::<$T, $N>([$($x as $T),*])↩
});↩
($T:ty; $N:ty, [], [$x1:expr]) => (↩
$crate::arr_impl!($T; $crate::arr::Inc<$T, $N>, [$x1], [])↩
);↩
($T:ty; $N:ty, [], [$x1:expr, $($x:expr),+]) => (↩
$crate::arr_impl!($T; $crate::arr::Inc<$T, $N>, [$x1], [$($x),+])↩
);↩
($T:ty; $N:ty, [$($y:expr),+], [$x1:expr]) => (↩
$crate::arr_impl!($T; $crate::arr::Inc<$T, $N>, [$($y),+, $x1], [])↩
);↩
($T:ty; $N:ty, [$($y:expr),+], [$x1:expr, $($x:expr),+]) => (↩
$crate::arr_impl!($T; $crate::arr::Inc<$T, $N>, [$($y),+, $x1], [$($x),+])↩
);↩
}↩
↩
/// Macro allowing for easy generation of Generic Arrays.↩
/// Example: `let test = arr![u32; 1, 2, 3];`↩
#[macro_export]↩
macro_rules! arr {↩
($T:ty; $(,)*) => ({↩
unsafe { $crate::transmute::<[$T; 0], $crate::GenericArray<$T, $crate::typenum::U0>>([]) }↩
});↩
($T:ty; $($x:expr),* $(,)*) => (↩
$crate::arr_impl!($T; $crate::typenum::U0, [], [$($x),*])↩
);↩
($($x:expr,)+) => (arr![$($x),+]);↩
() => ("""Macro requires a type, e.g. `let array = arr![u32; 1, 2, 3];`")↩
}↩
↩
mod doctests_only {↩
///↩
/// # With ellision↩
///↩
/// Testing that lifetimes aren't transmuted when they're ellided.↩
///↩
/// ```compile_fail↩
/// #[macro_use] extern crate generic_array;↩
/// fn main() {↩
/// fn unsound_lifetime_extension<'a, A>(a: &'a A) -> &'static A {↩
/// arr![&A; a][0]↩
/// }↩
/// }↩
/// ```↩
///↩
/// ```rust↩
/// #[macro_use] extern crate generic_array;↩
/// fn main() {↩
/// fn unsound_lifetime_extension<'a, A>(a: &'a A) -> &'a A {↩
/// arr![&A; a][0]↩
/// }↩
/// }↩
/// ```↩
///↩
/// # Without ellision↩
///↩
/// Testing that lifetimes aren't transmuted when they're specified explicitly.↩
///↩
/// ```compile_fail↩
/// #[macro_use] extern crate generic_array;↩
/// fn main() {↩
/// fn unsound_lifetime_extension<'a, A>(a: &'a A) -> &'static A {↩
/// arr![&'a A; a][0]↩
/// }↩
/// }↩
/// ```↩
///↩
/// ```compile_fail↩
/// #[macro_use] extern crate generic_array;↩
/// fn main() {↩
/// fn unsound_lifetime_extension<'a, A>(a: &'a A) -> &'static A {↩
/// arr![&'static A; a][0]↩
/// }↩
/// }↩
/// ```↩
///↩
/// ```rust↩
/// #[macro_use] extern crate generic_array;↩
/// fn main() {↩
/// fn unsound_lifetime_extension<'a, A>(a: &'a A) -> &'a A {↩
/// arr![&'a A; a][0]↩
/// }↩
/// }↩
/// ```↩
#[allow(dead_code)]↩
pub enum DocTests {}↩
}↩