[llvm-bugs] [Bug 39263] New: Clang wrongly reports duplicate member error on using recursive template

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39263

            Bug ID: 39263
           Summary: Clang wrongly reports duplicate member error on using
                    recursive template
           Product: clang
           Version: 7.0
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: leandro.dasilva at younicos.com
                CC: dgregor at apple.com, llvm-bugs at lists.llvm.org

I am using Clang 7.0 on Windows 10, but could reproduce the issue on Compiler
Explorer using different compiler versions.

The following code compiles fine on GCC (tested with 4.2 (!) and 4.8 and other
versions available on Compiler Explorer), and on MSVC 19 (again on CE).

But yields error on every clang I tried, both on my local machine as well as on
Compiler Explorer.

The code requires boost (tested with 1.52 and newer)

Code:

```
#include <boost/mpl/integral_c.hpp>

struct r_base {};

typedef long long r_value_t;

template<r_value_t N, r_value_t D = 1>
struct r : r_base
{
    static const r_value_t n = N;
    static const r_value_t d = D;
};

template<r_value_t X>
struct a : boost::mpl::integral_c<r_value_t, (X < 0) ? -X : X> {};

template<r_value_t U, r_value_t V>
struct g : g<V, U % V> {};

template<r_value_t U>
struct g<U, 0> : a<U> {};

template<typename T>
struct r_r
{
    static const r_value_t n = a<T::n>::value;
    static const r_value_t d = a<T::d>::value; // error happens here: d is
duplicate member
    static const r_value_t g = g<n, d>::value;
};

Clang reports the errors:
<source>:29:37: error: duplicate member 'd'

    static const r_value_t g = g<n, d>::value;

                                    ^
<source>:28:28: note: previous declaration is here

    static const r_value_t d = a<T::d>::value;

                           ^
<source>:29:38: error: expected ';' at end of declaration list

    static const r_value_t g = g<n, d>::value;

                                     ^
                                     ;

```

Thank you in advance.

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