[Bug c++/92918] New: Does not do name lookup when using from base class

[CoachHagins at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92918

            Bug ID: 92918
           Summary: Does not do name lookup when using from base class
           Product: gcc
           Version: 9.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: CoachHagins at gmail dot com
  Target Milestone: ---

This bug exists on all versions of the compiler I tried, including the current
branch.

Here is a link to compiler explorer with the code example:
https://godbolt.org/z/wYo-4n

And here is a copy/paste of the code.  Compile with "-std=c++17 -DSHOW_BUG"

It shows several similar cases where the code compiles, followed by the case
which does not compile.

-----


#include <cstddef>

class ThisCompilesOnGCC {
    static void impl(char const *);
public:
    template <typename T>
    [[nodiscard]] constexpr auto operator()(const T &t) const noexcept
    -> decltype(impl(t))
    {
        return impl(t);
    }
};
void thisCompilesOnGCC() {
    ThisCompilesOnGCC{}("42");
}

class Base01 {
protected:
    static void impl(char const *);
};
class ThisAlsoCompilesOnGCC : private Base01 {
    using Base01::impl;
public:
    template <typename T>
    [[nodiscard]] constexpr auto operator()(const T &t) const noexcept
    -> decltype(impl(t))
    {
        return impl(t);
    }
};
void thisAlsoCompilesOnGCC() {
    ThisAlsoCompilesOnGCC{}("42");
}

class Base02 {
protected:
    static void impl(char const *);
};
class ThisCompilesOnGCCToo : private Base02 {
    using Base02::impl;
    static void impl(int);
public:
    template <typename T>
    [[nodiscard]] constexpr auto operator()(const T &t) const noexcept
    -> decltype(impl(t))
    {
        return impl(t);
    }
};
void thisCompilesOnGCCToo() {
    ThisCompilesOnGCCToo{}("42");
}

#if defined (__clang__) || defined(SHOW_BUG)
// This compiles with clang - but not with gcc
class Base03 {
protected:
    static void impl(int);
};
class ThisDoesNotCompileOnGCC : private Base03 {
    using Base03::impl;
    static void impl(char const *);
public:
    template <typename T>
    [[nodiscard]] constexpr auto operator()(const T &t) const noexcept
    -> decltype(impl(t))
    {
        return impl(t);
    }
};
void thisDoesNotCompileOnGCC() {
    ThisDoesNotCompileOnGCC{}("42");
}
#endif