Implement type_of for anon consts on RHS of const items

Author: camelid

compiler/rustc_hir_analysis/src/collect/type_of.rs

@@ -103,6 +103,12 @@ fn const_arg_anon_type_of<'tcx>(icx: &ItemCtxt<'tcx>, arg_hir_id: HirId, span: S
             icx.lower_ty(ty)
         }
 
+        Node::Item(hir::Item { kind: hir::ItemKind::Const(_, ty, ..), .. })
+        | Node::ImplItem(hir::ImplItem { kind: hir::ImplItemKind::Const(ty, ..), .. })
+        | Node::TraitItem(hir::TraitItem { kind: hir::TraitItemKind::Const(ty, ..), .. }) => {
+            icx.lower_ty(ty)
+        }
+
         // This is not a `bug!` as const arguments in path segments that did not resolve to anything
         // will result in `type_of` never being fed.
         _ => Ty::new_error_with_message(