Fix rustdoc

src/librustdoc/clean/mod.rs

@@ -2897,7 +2897,14 @@ impl Clean<Type> for hir::Ty {
                 }
             }
             TyBareFn(ref barefn) => BareFunction(box barefn.clean(cx)),
-            TyImplTraitExistential(ref exist_ty, _, _) => ImplTrait(exist_ty.bounds.clean(cx)),
+            TyImplTraitExistential(hir_id, _, _) => {
+                match cx.tcx.hir.expect_item(hir_id.id).node {
+                    hir::ItemExistential(ref exist_ty) => {
+                        ImplTrait(exist_ty.bounds.clean(cx))
+                    },
+                    ref other => panic!("impl Trait pointed to {:#?}", other),
+                }
+            },
             TyInfer | TyErr => Infer,
             TyTypeof(..) => panic!("Unimplemented type {:?}", self.node),
         }

src/librustdoc/visit_ast.rs

@@ -559,6 +559,9 @@ impl<'a, 'tcx, 'rcx> RustdocVisitor<'a, 'tcx, 'rcx> {
                     om.impls.push(i);
                 }
             },
+            hir::ItemExistential(_) => {
+                // FIXME(oli-obk): actually generate docs for real existential items
+            }
         }
     }