dont ICE on ConstEvaluatable predicates

src/librustdoc/clean/mod.rs

@@ -350,12 +350,12 @@ fn clean(&self, cx: &mut DocContext<'_>) -> Option<WherePredicate> {
             ty::PredicateKind::RegionOutlives(pred) => pred.clean(cx),
             ty::PredicateKind::TypeOutlives(pred) => pred.clean(cx),
             ty::PredicateKind::Projection(pred) => Some(pred.clean(cx)),
+            ty::PredicateKind::ConstEvaluatable(..) => None,
 
             ty::PredicateKind::Subtype(..)
             | ty::PredicateKind::WellFormed(..)
             | ty::PredicateKind::ObjectSafe(..)
             | ty::PredicateKind::ClosureKind(..)
-            | ty::PredicateKind::ConstEvaluatable(..)
             | ty::PredicateKind::ConstEquate(..)
             | ty::PredicateKind::TypeWellFormedFromEnv(..) => panic!("not user writable"),
         }

src/test/rustdoc/const-generics/const-evaluatable-checked.rs

@@ -0,0 +1,5 @@
+#![crate_name = "foo"]
+#![feature(const_evaluatable_checked, const_generics)]
+#![allow(incomplete_features)]
+// make sure that `ConstEvaluatable` predicates dont cause rustdoc to ICE #77647
+pub struct Ice<const N: usize> where [(); N + 1]:;