[Bug c++/54309] New: type alias accessing class template enum type member fails
paul at preney dot ca
gcc-bugzilla@gcc.gnu.org
Sat Aug 18 05:16:00 GMT 2012
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54309
Bug #: 54309
Summary: type alias accessing class template enum type member
fails
Classification: Unclassified
Product: gcc
Version: 4.8.0
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: c++
AssignedTo: unassigned@gcc.gnu.org
ReportedBy: paul@preney.ca
Created attachment 28046
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=28046
Source code demonstrating the bug.
This is easier to see not working than to describe. The code that does not work
(i.e., "not ok: BUG" comment in the example) works if you replace the using
type alias with a typedef instead though (which means that is a work-around for
now).
This bug was tested with these versions of GCC:
g++ v4.7.0
g++ v4.8.0 (snapshot 20120812)
The error message (from GCC v4.8):
$ g++-4.8.0-alpha20120812 -std=c++11 gcc-cxx-bug.cxx
gcc-cxx-bug.cxx: In instantiation of ‘void func() [with T = int]’:
gcc-cxx-bug.cxx:25:13: required from here
gcc-cxx-bug.cxx:15:24: error: no type named ‘Stuff’ in ‘using test = class
Foo<T>’
typename test::Stuff b = test::Stuff::beta; // not ok: BUG
^
gcc-cxx-bug.cxx:15:24: error: no type named ‘Stuff’ in ‘using test = class
Foo<T>’
gcc-cxx-bug.cxx:15:24: error: no type named ‘Stuff’ in ‘using test = class
Foo<T>’
$
(I also tried this code with clang++ (v3.1) and it compiles successfully as
expected.)
It appears to only occur when a using type alias (i.e., the "test" alias in the
example) is used to access a template class' member that is an enum type (i.e.,
"Foo<T>::Stuff" in the example) when the class template parameter is not
hard-coded using the using type alias (i.e., Foo<T> is used but Foo<int> is
okay). The code triggering the issue follows and is attached.
template <typename T>
class Foo
{
public:
enum class Stuff { alpha, beta };
};
template <typename T>
void func()
{
typename Foo<T>::Stuff a = Foo<T>::Stuff::alpha; // ok
a = a;
using test = Foo<T>;
typename test::Stuff b = test::Stuff::beta; // not ok: BUG
b = b;
typedef Foo<T> test2;
typename test2::Stuff c = test2::Stuff::beta; // ok
c = c;
}
int main()
{
func<int>();
{
Foo<int>::Stuff a = Foo<int>::Stuff::alpha; // ok
a = a;
using test = Foo<int>;
typename test::Stuff b = test::Stuff::beta; // ok
b = b;
typedef Foo<int> test2;
typename test2::Stuff c = test2::Stuff::beta; // ok
c = c;
}
}
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