[llvm-bugs] [Bug 50496] New: Use of auto template parameters breaks partial specialization

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50496

            Bug ID: 50496
           Summary: Use of auto template parameters breaks partial
                    specialization
           Product: clang
           Version: trunk
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++17
          Assignee: unassignedclangbugs at nondot.org
          Reporter: eniebler at boost.org
                CC: blitzrakete at gmail.com, erik.pilkington at gmail.com,
                    llvm-bugs at lists.llvm.org, richard-llvm at metafoo.co.uk

The following code fails to compile, but should:

  inline constexpr struct S {} C {};

  template <class S>
  struct traits;

  template <auto& A>
  struct odd {};

  template <auto& A>
  struct traits<odd<A>> {};

  int main() {
    traits<odd<C>> t; // ERROR HERE
  }


The commented line in main generated the following error:

  error: implicit instantiation of undefined template 'traits<odd<C>>'
      traits<odd<C>> t;
                     ^

The partial specialization with the auto template parameter fails to match the
instantiation.

GCC accepts the code. A slight tweak causes clang to accept the code (replacing
`auto&` with `const auto&`.

https://godbolt.org/z/M7Y9nvva3

-- 
You are receiving this mail because:
You are on the CC list for the bug.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-bugs/attachments/20210526/f05ffaf6/attachment.html>