[Bug fortran/107721] Lost typespec with constant expressions using array constructors and parentheses

["kargl at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107721

kargl at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kargl at gcc dot gnu.org

--- Comment #5 from kargl at gcc dot gnu.org ---
(In reply to Jerry DeLisle from comment #4)
>
>   print *, ([1.0]) works quite well.
> 
> We have, therefore an expr.
> 
> In array.cc we have gfc_match_array_constructor.  As far as I can tell we
> are matching the ac-implied-do, however we are not even trying to match expr.
> 
> Let's see what we can do about it.
>

Yes, it's an expr.  The matching happens in gfc_match_array_constructor()
when you get to lines 1311ff

  for (;;)
    {
      m = match_array_cons_element (&head);
      if (m == MATCH_ERROR)
        goto cleanup;
      if (m == MATCH_NO)
        goto syntax;

      if (gfc_match_char (',') == MATCH_NO)
        break;
    }

If you deep dive into match_array_cons_element(), you see

  m = match_array_list (result);
  if (m != MATCH_NO)
    return m;

  m = gfc_match_expr (&expr);
  if (m != MATCH_YES)
    return m;

There's your expression mapping.  The problem is that for
[integer :: ([1.0])] **  2, simplification of the expression
([1.0]) returns ([1.0]) and expr_type of EXPR_OP.

So, when we walk the array constructor in lines 1368ff

      if (gfc_numeric_ts (&ts))
        {
          m = walk_array_constructor (&ts, head);
          if (m == MATCH_ERROR)
            return m;
        }

the walker cannot apply a type conversion.

My take is that simplification of ([1.0]) needs to reduce
this to [1.0], which then allows the code to compile.  I 
had a patch that did this, but it failed with (([1.0])).
I modified the patch to accept (([1.0])), and it of course
failed with ((([1.0]))).