[Bug c++/94553] New: Revisit [basic.scope.declarative]/4.2

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94553

            Bug ID: 94553
           Summary: Revisit [basic.scope.declarative]/4.2
           Product: gcc
           Version: 10.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mpolacek at gcc dot gnu.org
  Target Milestone: ---

<http://eel.is/c++draft/basic.scope#declarative-4.2> has a note:
A structured binding ([dcl.struct.bind]), namespace name ([basic.namespace]),
or class template name ([temp.pre]) must be unique in its declarative region.
but we don't fully implement that.  Consequently, the following is
accepts-valid.  (The structured binding part was added in CWG 2289.)

void
f ()
{
  int arr[1] = { 1 };
  struct A { };
  auto [A] = arr; // error
  auto [B] = arr;
  struct B { }; // error
}

struct C { };
template<typename> int C; // error
template<typename> int D;
struct D { }; // error