[Bug c++/87536] New: Illegal recursive concept leads to compiler ICE

[blelbach at cct dot lsu.edu]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87536

            Bug ID: 87536
           Summary: Illegal recursive concept leads to compiler ICE
           Product: gcc
           Version: c++-concepts
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: blelbach at cct dot lsu.edu
  Target Milestone: ---

GCC concepts seem to allow the use of the name of a concept in the definition
of the concept itself. This appears to allow me to trick GCC into infinitely
recursing and blowing up with an ICE:

https://godbolt.org/z/p8Yuo0

A repro is as follows:

template <typename T>
bool concept X = X<T>;

template <X> struct A{};
A<int> a;