[Bug fortran/104651] [OOP] CLASS with assumed-size/assumed-rank array

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104651

--- Comment #3 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to kargl from comment #1)
> (In reply to Tobias Burnus from comment #0)
> > Error: Rank mismatch in argument ‘x’ at (1) (rank-1 and rank-2)
> > Error: Rank mismatch in argument ‘y’ at (1) (rank-2 and rank-1)
> >
> > subroutine bar(x)
> >   class(t) :: x(*)
> >
> > subroutine bar2(y)
> >   class(t) :: y(5,10)
> 
> Error look correct to me.  Interfaces are resolved by type, kind, and rank;
> sometimes referred to TKR.  Is there an exception for class?

Passing an array of any rank or even array element to ASSUMED-SIZE and
EXPLICIT-SIZE ARRAYS is a Fortran 66 feature which still exists. For those, the
simple (contiguous) byte stream ("storage sequence") is passed – and the
partition of that stream into array bounds/elements is determined by the
callee.

Example:
    integer A(10), B(10,10), C(10,10,10)
    call foo(A,A); call foo(B,B); call foo(C,C)
  contains
    subroutine foo(x,y)
      integer, intent(in) :: x(5:7,*), y(5,2)
    end
  end

This works just fine in gfortran. But for CLASS the like-wise code does not
work.

>From the standard (allocatable/pointers and deferred-shape arrays are in
section):


Fortran 2018, "15.5.2.4 Ordinary dummy variables":

"If a dummy argument is an assumed-shape array, the rank of the actual argument
shall be the same as the rank of the dummy argument ..."

As this restriction does not exist for assumed-size/explicit-size array
dummies, those are permitted. Some more wording is then in "15.5.2.11 Sequence
association":

"Sequence association only applies when the dummy argument is an explicit-shape
or assumed-size array. The rest of this subclause only applies in that case.
"An actual argument represents an element sequence if it is an array
expression, an array element designator, a default character scalar, or a
scalar of type character with the C character kind (18.2.2). [...]"

For details, see the two sections mentioned above as I did leave out some bits
related to this discussion.