http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59383
Bug ID: 59383
Summary: typedef propagation with template base class using the
same name is wrong
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: gmarkhor at gmail dot com
I am using g++ 4.8.1. Consider the following code (compiled as g++ -std=c++11
-c test.cc):
#include <type_traits>
template <typename F, typename S>
struct TypePair {
typedef F First;
typedef S Second;
};
template <int I>
class Base {
public:
typedef TypePair<Base, Base> Family;
typedef Base ParentType;
};
template <int I>
class Derived : public Base<I> {
public:
typedef TypePair<Derived, typename Derived::Family::First> Family;
typedef typename Family::Second ParentType;
};
static_assert(std::is_same<Base<1>, Derived<1>::ParentType>::value, "Error");
The static assertion is failed. Clang ver. 3.2 and 3.3 and 3.4 compiles this
code well.
If you remove the template from Base:
#include <type_traits>
template <typename F, typename S>
struct TypePair {
typedef F First;
typedef S Second;
};
class Base {
public:
typedef TypePair<Base, Base> Family;
typedef Base ParentType;
};
template <int I>
class Derived : public Base {
public:
typedef TypePair<Derived, typename Derived::Family::First> Family;
typedef typename Family::Second ParentType;
};
static_assert(std::is_same<Base, Derived<1>::ParentType>::value, "Error");
then everything becomes OK. The other way to make it work is to remove template
from Derived and inherit from an explicit Base<1>:
#include <type_traits>
template <typename F, typename S>
struct TypePair {
typedef F First;
typedef S Second;
};
template <int I>
class Base {
public:
typedef TypePair<Base, Base> Family;
typedef Base ParentType;
};
class Derived : public Base<1> {
public:
typedef TypePair<Derived, typename Derived::Family::First> Family;
typedef typename Family::Second ParentType;
};
static_assert(std::is_same<Base<1>, Derived::ParentType>::value, "Error");
I am not sure what standard says about this, but it seems a bug.
