[Bug c++/84788] New: Parenthesis changes a constant to non-constant

[tuliom at linux dot vnet.ibm.com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84788

            Bug ID: 84788
           Summary: Parenthesis changes a constant to non-constant
           Product: gcc
           Version: 8.0.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: tuliom at linux dot vnet.ibm.com
  Target Milestone: ---

Reproduced with GCC 8.0.1 rev. 258059:

$ cat test-cxx.cpp 
template <int kKeybits>
class PackedCache {
 public:
  static const int kValuebits = 7;
  static const int kValueMask = 1 << ((kValuebits)-1);
};

$ g++ -c test-cxx.cpp
test-cxx.cpp:5:53: error: non-constant in-class initialization invalid for
static member ‘PackedCache<kKeybits>::kValueMask’
   static const int kValueMask = 1 << ((kValuebits)-1);
                                                     ^
test-cxx.cpp:5:53: note: (an out of class initialization is required)


If the parenthesis around kValuebits is removed, the error disappears, i.e.:
  static const int kValueMask = 1 << (kValuebits-1);

I can't reproduce this error with GCC 7.
This file used to build with rev. 253122.
I can build the file when using -std=gnu++11.