Hi,
when preparing for standardization in WG14 of this feature we ran into an inconsistency with gcc.
For declarations with __auto_type gcc accepts all C qualifiers in a reasonable way, whereas clang refuses restrict and _Atomic. The diagnostics that clang gives seem to indicate that these have simply not yet been considered

restrict requires a pointer or reference ('__auto_type' is invalid)
_Atomic cannot be applied to type '__auto_type' which is not trivially copyable

A small example that compiles with gcc but not with clang:

int main() {
  double x = 37;
  // clang doesn't accept that
  __auto_type restrict xr = &x;
  restrict __auto_type rx = &x;
  __auto_type _Atomic xa = x;
   _Atomic __auto_type ax = x;
}

Thanks
Jens