add test for ICE with associated_const_equality #108220

Fixes #108220

tests/ui/generic-const-items/assoc-const-AnonConst-ice-108220.rs

@@ -0,0 +1,35 @@
+// ICE assertion failed: matches!(self.def_kind(ct.def.did), DefKind :: AnonConst)
+// issue: rust-lang/rust#108220
+//@ check-pass
+
+#![feature(associated_const_equality)]
+#![allow(unused)]
+
+use std::marker::PhantomData;
+
+pub struct NoPin;
+
+pub trait SetAlternate<const A: u8> {}
+
+impl SetAlternate<0> for NoPin {}
+
+pub trait PinA<PER> {
+    const A: u8;
+}
+
+impl<PER> PinA<PER> for NoPin {
+    const A: u8 = 0;
+}
+
+pub trait Pins<USART> {}
+
+impl<USART, T, const TA: u8> Pins<USART> for T where
+    T: PinA<USART, A = { TA }> + SetAlternate<TA>
+{
+}
+
+struct Serial<USART>(PhantomData<USART>);
+
+impl<USART> Serial<USART> where NoPin: Pins<USART> {}
+
+fn main() {}