74 lines
1.5 KiB
Rust
74 lines
1.5 KiB
Rust
//@ build-pass
|
|
|
|
#![allow(incomplete_features)]
|
|
#![feature(generic_const_exprs)]
|
|
|
|
trait Collate<Op> {
|
|
type Pass;
|
|
type Fail;
|
|
|
|
fn collate(self) -> (Self::Pass, Self::Fail);
|
|
}
|
|
|
|
impl<Op> Collate<Op> for () {
|
|
type Pass = ();
|
|
type Fail = ();
|
|
|
|
fn collate(self) -> ((), ()) {
|
|
((), ())
|
|
}
|
|
}
|
|
|
|
trait CollateStep<X, Prev> {
|
|
type Pass;
|
|
type Fail;
|
|
fn collate_step(x: X, prev: Prev) -> (Self::Pass, Self::Fail);
|
|
}
|
|
|
|
impl<X, P, F> CollateStep<X, (P, F)> for () {
|
|
type Pass = (X, P);
|
|
type Fail = F;
|
|
|
|
fn collate_step(x: X, (p, f): (P, F)) -> ((X, P), F) {
|
|
((x, p), f)
|
|
}
|
|
}
|
|
|
|
struct CollateOpImpl<const MASK: u32>;
|
|
trait CollateOpStep {
|
|
type NextOp;
|
|
type Apply;
|
|
}
|
|
|
|
impl<const MASK: u32> CollateOpStep for CollateOpImpl<MASK>
|
|
where
|
|
CollateOpImpl<{ MASK >> 1 }>: Sized,
|
|
{
|
|
type NextOp = CollateOpImpl<{ MASK >> 1 }>;
|
|
type Apply = ();
|
|
}
|
|
|
|
impl<H, T, Op: CollateOpStep> Collate<Op> for (H, T)
|
|
where
|
|
T: Collate<Op::NextOp>,
|
|
Op::Apply: CollateStep<H, (T::Pass, T::Fail)>,
|
|
{
|
|
type Pass = <Op::Apply as CollateStep<H, (T::Pass, T::Fail)>>::Pass;
|
|
type Fail = <Op::Apply as CollateStep<H, (T::Pass, T::Fail)>>::Fail;
|
|
|
|
fn collate(self) -> (Self::Pass, Self::Fail) {
|
|
<Op::Apply as CollateStep<H, (T::Pass, T::Fail)>>::collate_step(self.0, self.1.collate())
|
|
}
|
|
}
|
|
|
|
fn collate<X, const MASK: u32>(x: X) -> (X::Pass, X::Fail)
|
|
where
|
|
X: Collate<CollateOpImpl<MASK>>,
|
|
{
|
|
x.collate()
|
|
}
|
|
|
|
fn main() {
|
|
dbg!(collate::<_, 5>(("Hello", (42, ('!', ())))));
|
|
}
|