[Bug c++/87765] New: Internal compiler error: coerce_template_parms (8.2) or cxx_eval_constant_expression (trunk)

[curlypaul924 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87765

            Bug ID: 87765
           Summary: Internal compiler error: coerce_template_parms (8.2)
                    or cxx_eval_constant_expression (trunk)
           Product: gcc
           Version: 8.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: curlypaul924 at gmail dot com
  Target Milestone: ---

The following syntactically valid program produces an ICE in
coerce_template_parms on gcc 8.2:

template <int N>
using foo = int;

struct A {
  constexpr int bar() const { return 42; }
};

void baz(A a) {
  [=](auto c) { return foo<a.bar()> { }; };
}

creduce produced a syntactically invalid program which also causes ICE:

template <int N>
using foo = int;

struct A {
  int bar();
};

void baz(A a) {
  [](auto foo<a.bar()>
}

x86-64 gcc trunk on godbolt.org also ICEs, but in cxx_eval_constant_expression.

Clang accepts the first snippet, but gcc 7.3 rejects it with "error:
'__closure' is not a constant expression".

Possibly related to (or duplicate of) Bug 86960.