[Bug c++/85553] New: [8/9 Regression] cannot list-initialize a variable of type std::nullptr_t

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85553

            Bug ID: 85553
           Summary: [8/9 Regression] cannot list-initialize a variable of
                    type std::nullptr_t
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
                CC: paolo at gcc dot gnu.org
  Target Milestone: ---

THe fix for PR 70808 (r259303) causes this valid code to be rejected:

using T = decltype(nullptr);
const constexpr T foo{};


np.cc:2:23: error: '(const T)nullptr' is not a constant expression
 const constexpr T foo{};
                       ^

Reverting r259303 fixes it.