Add 82268

Issue: rust-lang/rust#82268

ices/82268.rs

@@ -0,0 +1,82 @@
+#![feature(const_generics, const_evaluatable_checked)]
+
+struct True;
+struct False;
+
+trait ConstBool {
+    type Val;
+}
+struct TypeBool<const X: bool>;
+
+impl ConstBool for TypeBool<true> {
+    type Val = True;
+}
+
+impl ConstBool for TypeBool<false> {
+    type Val = False;
+}
+
+trait Collate<const MASK: u32> {
+    type Pass;
+    type Fail;
+
+    fn collate(self) -> (Self::Pass, Self::Fail);
+}
+
+impl<const MASK: u32> Collate<MASK> 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 TypeBool<true> {
+    type Pass = (X, P);
+    type Fail = F;
+
+    fn collate_step(x: X, (p, f): (P, F)) -> ((X, P), F) {
+        ((x, p), f)
+    }
+}
+
+impl<X, P, F> CollateStep<X, (P, F)> for TypeBool<false> {
+    type Pass = P;
+    type Fail = (X, F);
+
+    fn collate_step(x: X, (p, f): (P, F)) -> (P, (X, F)) {
+        (p, (x, f))
+    }
+}
+
+impl<H, T: Collate<{ MASK >> 1 }>, const MASK: u32> Collate<MASK> for (H, T)
+where
+    TypeBool<{ 1 == MASK & 1 }>: CollateStep<H, (T::Pass, T::Fail)>,
+{
+    type Pass =
+        <TypeBool<{ 1 == MASK & 1 }> as CollateStep<H, (T::Pass, T::Fail)>>::Pass;
+    type Fail =
+        <TypeBool<{ 1 == MASK & 1 }> as CollateStep<H, (T::Pass, T::Fail)>>::Fail;
+
+    fn collate(self) -> (Self::Pass, Self::Fail) {
+        <TypeBool<{ 1 == MASK & 1 }>
+         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<MASK> {
+    x.collate()
+}
+
+fn main() {
+    dbg!(collate::<_,3>((4, ('!',()))));
+}