[Bug c++/84325] [8 Regression] internal compiler error, in cxx_eval_constant_expression gcc/cp/constexpr.c:4740

[mpolacek at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84325

--- Comment #6 from Marek Polacek <mpolacek at gcc dot gnu.org> ---
If I tweak the testcase like this:

struct seconds { int i_{0}; constexpr seconds (int) {} };
template <char... _Digits> constexpr seconds operator""_s() {
  return seconds(0);
}
constexpr seconds operator""_s(long double i) {
  return seconds(0);
}
template<class TYPE>
struct Param {
  constexpr static inline seconds time_to_wait{10_s};
};
struct Empty {};
Param<Empty> p;

then it's accepted by clang++ and ICEs the same.  And if I apply this then it's
accepted by G++, too:

--- a/gcc/cp/tree.c
+++ b/gcc/cp/tree.c
@@ -3091,7 +3091,7 @@ replace_placeholders_r (tree* t, int* walk_subtrees,
void* data_)
   replace_placeholders_t *d = static_cast<replace_placeholders_t*>(data_);
   tree obj = d->obj;

-  if (TREE_CONSTANT (*t))
+  if (!TYPE_P (*t) && TREE_CONSTANT (*t))
     {
       *walk_subtrees = false;
       return NULL_TREE;