Hi again,
On 04/27/2013 02:56 AM, Jason Merrill wrote:
Why should id_expression_or_member_access_p be false?
"declval<T>().dummy" is a class member access (5.2.5) regardless of
what kind of member dummy is.
today I have been able to spend some more time on the issue, and I think
the attached further reduced testcase summarizes rather well what I
figured out.
Assuming as obvious that we don't want to crash on it, the interesting
issue is whether we want the static_asserts to both fail or succeed: in
practice, a rather recent ICC I have at hand fails both; a rather recent
clang++ passes both (consistently with the expectation of Bug
submitter). In fact, as I'm reading now 7.1.6.2/4, since we are dealing
with a class member access in any case, it may well be possible that
*ICC* is right. And then a tiny patch like the attached works for me to
obtain the same behavior for GCC (passes testing etc; it's the first
"stupid" thing I tried days ago ;)
FWIW, the attached testcase also explains pretty well why my earlier
hack appeared to work, in the sense of recent clang++: we ended up
calling cp_build_reference_type on the type.
Overall, I think the situation is rather clear by now. What do you think?
Thanks!
Paolo.
////////////////////////
template<typename T>
T&& declval();
template<typename, typename>
struct is_same
{ static constexpr bool value = false; };
template<typename T>
struct is_same<T, T>
{ static constexpr bool value = true; };
struct A
{
static const int dummy = 0;
};
static_assert(!is_same<decltype(declval<A>().dummy), const int>::value, "");
static_assert(is_same<decltype(declval<A>().dummy), const int&>::value, "");
Index: semantics.c
===================================================================
--- semantics.c (revision 198359)
+++ semantics.c (working copy)
@@ -5398,6 +5398,7 @@ finish_decltype_type (tree expr, bool id_expressio
break;
case COMPONENT_REF:
+ case COMPOUND_EXPR:
mark_type_use (expr);
type = is_bitfield_expr_with_lowered_type (expr);
if (!type)
