Do not ICE on AnonConsts in diagnostic_hir_wf_check

Author: gurry

compiler/rustc_hir_analysis/src/hir_wf_check.rs

@@ -163,15 +163,17 @@ fn diagnostic_hir_wf_check<'tcx>(
                 kind: hir::GenericParamKind::Type { default: Some(ty), .. },
                 ..
             }) => vec![*ty],
-            hir::Node::AnonConst(_)
-                if let Some(const_param_id) =
-                    tcx.hir().opt_const_param_default_param_def_id(hir_id)
+            hir::Node::AnonConst(_) => {
+                if let Some(const_param_id) = tcx.hir().opt_const_param_default_param_def_id(hir_id)
                     && let hir::Node::GenericParam(hir::GenericParam {
                         kind: hir::GenericParamKind::Const { ty, .. },
                         ..
-                    }) = tcx.hir_node_by_def_id(const_param_id) =>
-            {
-                vec![*ty]
+                    }) = tcx.hir_node_by_def_id(const_param_id)
+                {
+                    vec![*ty]
+                } else {
+                    vec![]
+                }
             }
             ref node => bug!("Unexpected node {:?}", node),
         },

tests/crashes/122989.rs

@@ -0,0 +1,42 @@
+// Regression test for ICE #122989
+trait Traitor<const N: N<2> = 1, const N: N<2> = N> {
+//~^ ERROR the name `N` is already used for a generic parameter in this item's generic parameters
+//~| ERROR cycle detected when computing type of `Traitor::N`
+//~| ERROR cycle detected when computing type of `Traitor::N`
+//~| ERROR the trait `Traitor` cannot be made into an object
+//~| ERROR the trait `Traitor` cannot be made into an object
+//~| ERROR the trait `Traitor` cannot be made into an object
+//~| ERROR the trait `Traitor` cannot be made into an object
+//~| ERROR `(dyn N<2> + 'static)` is forbidden as the type of a const generic parameter
+//~| ERROR `(dyn N<2> + 'static)` is forbidden as the type of a const generic parameter
+//~| WARN trait objects without an explicit `dyn` are deprecated
+//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+//~| WARN trait objects without an explicit `dyn` are deprecated
+//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+//~| WARN trait objects without an explicit `dyn` are deprecated
+//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+    fn N(&N) -> N<2> {
+    //~^ ERROR the trait `Traitor` cannot be made into an object
+    //~| WARN anonymous parameters are deprecated and will be removed in the next edition
+    //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2018!
+    //~| WARN trait objects without an explicit `dyn` are deprecated
+    //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+    //~| WARN trait objects without an explicit `dyn` are deprecated
+    //~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+        M
+        //~^ ERROR cannot find value `M` in this scope
+    }
+}
+
+trait N<const N: Traitor<2> = 12> {}
+//~^ ERROR cycle detected when computing type of `N::N`
+//~| ERROR cycle detected when computing type of `N::N`
+//~| ERROR the trait `Traitor` cannot be made into an object
+//~| ERROR the trait `Traitor` cannot be made into an object
+//~| ERROR `(dyn Traitor<2, {const error}> + 'static)` is forbidden as the type of a const generic parameter
+//~| WARN trait objects without an explicit `dyn` are deprecated
+//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+//~| WARN trait objects without an explicit `dyn` are deprecated
+//~| WARN this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
+
+fn main() {}