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use std::any::TypeId;
use std::mem::{transmute_copy, ManuallyDrop};
use paste::paste;
use seq_macro::seq;
use util_macros::sub;
pub trait Tuple: sealed::Sealed
{
/// `Self` with the given type added as the last element.
///
/// `(String, i32, u8)::WithElementAtEnd<Path> = (String, i32, u8, Path)`
///
/// # Important note
/// If `Self` has 16 elements, this will be `()`. The reason for this is that the
/// `Tuple` trait is only implemented for tuples with up to and including 16 elements.
type WithElementAtEnd<NewElem>: Tuple;
/// `Self` without the last element.
///
/// `(u16, AtomicU8)::WithoutLastElement = (u16,)`
type WithoutLastElement: Tuple;
/// The last element of `Self`.
type LastElement;
/// Pops the last element from this tuple, returning the new tuple and the popped
/// element.
fn pop_last(self) -> (Self::WithoutLastElement, Self::LastElement);
}
/// Used to make all elements of a tuple type wrapped in [`Option`].
pub trait IntoInOptions
{
type InOptions: WithOptionElements;
fn into_in_options(self) -> Self::InOptions;
}
/// A tuple with all elements wrapped in [`Option`].
pub trait WithOptionElements
{
fn take<Element: 'static>(&mut self) -> TakeOptionElementResult<Element>;
}
/// Using the type system, reduces the elements of a tuple to a single one. Each element
/// determines itself how it is handled.
pub trait Reduce<Operation>
{
type Out;
}
pub trait ReduceElement<Accumulator, Operation>
{
type Return;
}
/// The result of trying to [`take`] a element from a implementation of
/// [`WithOptionElements`].
///
/// [`take`]: WithOptionElements::take
pub enum TakeOptionElementResult<Element>
{
/// The element was succesfully taken.
Found(Element),
/// The element is not a element of the tuple.
NotFound,
/// The element has already been taken
AlreadyTaken,
}
macro_rules! tuple_reduce_elem_tuple {
(overflow) => {
()
};
($index: tt) => {
paste! {
[<Elem $index>]::Return
}
};
}
macro_rules! elem_type_by_index {
(overflow) => {
()
};
($index: tt) => {
paste! {
[<Elem $index>]
}
};
}
macro_rules! elem_by_index {
(overflow) => {
()
};
($index: tt, $self: ident) => {
$self.$index
};
}
macro_rules! all_except_last {
(start $($rest: tt)*) => {
all_except_last!(@[] $($rest)*)
};
(@[$($included_elem: ident,)*] $elem: ident $($rest: tt)+) => {
all_except_last!(@[$($included_elem,)* $elem,] $($rest)*)
};
(@[$($included_elem: expr,)*] ($elem: expr) $($rest: tt)+) => {
all_except_last!(@[$($included_elem,)* $elem,] $($rest)*)
};
(@[$($included_elem: ident,)*] $elem: ident) => {
($($included_elem,)*)
};
(@[$($included_elem: expr,)*] $elem: expr) => {
($($included_elem,)*)
};
(@[]) => {
()
};
}
macro_rules! impl_tuple_traits {
($cnt: tt) => {
seq!(I in 0..$cnt {
impl< #(Elem~I,)*> Tuple for (#(Elem~I,)*)
{
type WithElementAtEnd<NewElem> = (#(Elem~I,)* NewElem,);
type WithoutLastElement = all_except_last!(start #(Elem~I)*);
type LastElement = sub!($cnt - 1, elem_type_by_index);
fn pop_last(self) -> (Self::WithoutLastElement, Self::LastElement)
{
(
all_except_last!(start #((self.I))*),
sub!($cnt - 1, elem_by_index, (self))
)
}
}
impl< #(Elem~I,)*> sealed::Sealed for (#(Elem~I,)*)
{
}
impl<#(Element~I: 'static,)*> IntoInOptions for (#(Element~I,)*)
{
type InOptions = (#(Option<Element~I>,)*);
fn into_in_options(self) -> Self::InOptions
{
#![allow(clippy::unused_unit)]
(#(Some(self.I),)*)
}
}
impl<#(Element~I: 'static,)*> WithOptionElements for (#(Option<Element~I>,)*)
{
fn take<Element: 'static>(&mut self)
-> TakeOptionElementResult<Element>
{
#(
if TypeId::of::<Element~I>() == TypeId::of::<Element>() {
let input = match self.I.take() {
Some(input) => ManuallyDrop::new(input),
None => {
return TakeOptionElementResult::AlreadyTaken;
}
};
return TakeOptionElementResult::Found(
// SAFETY: It can be transmuted safely since it is the
// same type and the type is 'static
unsafe { transmute_copy(&input) }
);
}
)*
TakeOptionElementResult::NotFound
}
}
paste! {
impl<Operation, #(Elem~I,)*> Reduce<Operation> for (#(Elem~I,)*)
where
#(
Elem~I: ReduceElement<
sub!(I - 1, tuple_reduce_elem_tuple), Operation
>,
)*
{
type Out = sub!($cnt - 1, tuple_reduce_elem_tuple);
}
}
});
};
}
seq!(N in 0..16 {
impl_tuple_traits!(N);
});
seq!(I in 0..16 {
impl< #(Elem~I,)*> Tuple for (#(Elem~I,)*)
{
type WithElementAtEnd<NewElem> = ();
type WithoutLastElement = all_except_last!(start #(Elem~I)*);
type LastElement = Elem15;
fn pop_last(self) -> (Self::WithoutLastElement, Self::LastElement)
{
(
all_except_last!(start #((self.I))*),
self.15
)
}
}
impl< #(Elem~I,)*> sealed::Sealed for (#(Elem~I,)*)
{
}
});
mod sealed
{
pub trait Sealed {}
}
|
