https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117782
--- Comment #2 from kugan at gcc dot gnu.org ---
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -1194,6 +1194,7 @@ write_unscoped_name (const tree decl)
in a local function scope. A lambda can also be mangled in the
scope of a default argument. */
gcc_assert (context == global_namespace
+ || TREE_CODE (context) == RECORD_TYPE
|| TREE_CODE (context) == PARM_DECL
|| TREE_CODE (context) == FUNCTION_DECL);
Fixes.
