https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82336
--- Comment #3 from Nathan Sidwell <nathan at gcc dot gnu.org> --- When checking the default arg during parsing, we perform an implicit conversion inside an unevaluated_operand context. That's needed to fix 54198, where an ill-formed instantiation occurs otherwise. However, here, that implicit conversion is altering arg itself, via reshape_init, and we lose an enclosing target_expr.
