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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Invalid private member diagnostic of template using with decltype of private member method"
   href="https://bugs.llvm.org/show_bug.cgi?id=42348">42348</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Invalid private member diagnostic of template using with decltype of private member method
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>andyg1001@hotmail.co.uk
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>The following code fails to compile with an erroneous error "'Impl' is a
private member of 'S<void>'":

  template <typename> struct S
    {
    private:
    template <typename> static constexpr auto Impl();

    public:
    template <typename X> using U = decltype(Impl<X>());
    };

  template <typename T> template <typename>
  constexpr auto S<T>::Impl() { }

  using X = S<void>::U<void>;

The above code compiles in gcc et al.  Making the following change allows
compilation:

  template <typename> struct S
    {
    private:
    struct W
      {
      template <typename> static constexpr auto Impl();
      };

    public:
    template <typename X> using U = decltype(W::template Impl<X>());
    };

  template <typename T> template <typename>
  constexpr auto S<T>::W::Impl()
    { }</pre>
        </div>
      </p>


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      <ul>
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