https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100032
Patrick Palka <ppalka at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Target Milestone|--- |8.5
CC| |jason at gcc dot gnu.org
Summary|renaming alias template |[8/9/10/11 Regression]
|that also adds |renaming alias template
|cv-qualifiers is deemed |that also adds
|equivalent to underlying |cv-qualifiers is deemed
|template |equivalent to underlying
| |template
--- Comment #1 from Patrick Palka <ppalka at gcc dot gnu.org> ---
We started accepting the testcase after r208152.
I tried making get_underlying_template look through an alias only if the
underlying type is unqualified:
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6574,6 +6574,8 @@ get_underlying_template (tree tmpl)
/* The underlying type may have been ill-formed. Don't proceed. */
if (!orig_type)
break;
+ if (TYPE_QUALS (orig_type) != TYPE_UNQUALIFIED)
+ break;
tree tinfo = TYPE_TEMPLATE_INFO_MAYBE_ALIAS (orig_type);
if (!tinfo)
break;
but this also makes us (incorrectly?) reject
template <template<class> class> struct X { };
template <class> struct Y { };
template <class T> using Z = const Y<T>;
template <class T> using W = Z<T>;
using U = X<Z>;
using U = X<W>;
because the underlying type of W for some reason already has the const
qualifier, so get_underlying_template(W) yields W and we deem W not equivalent
to Z.
