[Bug c++/78511] New: ICE on using concept name as a "requires" parameter

["gcc-bugzilla at minijackson dot 33mail.com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78511

            Bug ID: 78511
           Summary: ICE on using concept name as a "requires" parameter
           Product: gcc
           Version: c++-concepts
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gcc-bugzilla at minijackson dot 33mail.com
  Target Milestone: ---

GCC version and system:

gcc (Gentoo 6.2.0-r1 p1.1) 6.2.0


Compilation options:

-altivec -awt -cilk cxx -debug -doc -fixed-point fortran gcj -go -graphite
-hardened -jit -libssp -mpx multilib nls nptl -objc -objc++ -objc-gc openmp pch
-pie -regression-test sanitize -ssp -vanilla vtv


Example program (test.cpp):

template <typename T>
concept bool A = true;

template <typename T>
concept bool B = requires(A a) {
        a;
}


Command line:

g++ -fconcepts -std=c++1z test.cpp


Error:

test.cpp:5:27: internal compiler error: in synthesize_implicit_template_parm,
at cp/parser.c:37866
 concept bool B = requires(A a) {
                           ^


test.ii generated file:

# 1 "test.cpp"
# 1 "<built-in>"
# 1 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 1 "<command-line>" 2
# 1 "test.cpp"
template <typename T>
concept bool A = true;

template <typename T>
concept bool B = requires(A a) {
 a;
}