https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113340
--- Comment #2 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
I suppose the following would be one way to fix it:
--- a/gcc/cp/decl2.cc
+++ b/gcc/cp/decl2.cc
@@ -312,6 +312,12 @@ maybe_retrofit_in_chrg (tree fn)
basetype = TREE_TYPE (TREE_VALUE (arg_types));
arg_types = TREE_CHAIN (arg_types);
+ if (!DECL_ARGUMENTS (fn))
+ {
+ gcc_checking_assert (seen_error ());
+ return;
+ }
+
parms = DECL_CHAIN (DECL_ARGUMENTS (fn));
/* If this is a subobject constructor or destructor, our caller will
