[Bug c++/85278] New: [concepts] Garbled diagnostic

[reichelt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85278

            Bug ID: 85278
           Summary: [concepts] Garbled diagnostic
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Keywords: diagnostic
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: reichelt at gcc dot gnu.org
            Blocks: 67491
  Target Milestone: ---

The testcase gcc/testsuite/g++.dg/concepts/req2.C produces a broken diagnostic
since GCC 6.1.0:

req2.C:18:14: error: cannot call function 'void f2(auto:2) requires (<requires
(#'decltype_type' not supported by simple_type_specifier#x#'decltype_type' not
supported by direct_abstract_declarator#) <valid-expression (-x)>> [with auto:2
= void*]'

The offending testcase can be reduced to:

======================================================
void f2(auto a)
  requires requires (decltype(a) x) { -x; }
{ }

int main() {
  f2((void*)0);
}
======================================================


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67491
[Bug 67491] [meta-bug] concepts issues