[Bug fortran/49213] New: [OOP] gfortran rejects structure constructor expression

["neil.n.carlson at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49213

           Summary: [OOP] gfortran rejects structure constructor
                    expression
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: fortran
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: neil.n.carlson@gmail.com


In the following program type-compatible variables are used as an expression in
a structure constructor for an allocatable CLASS(S) component.  In the first
case a TYPE(S) variable is used, and in the second a TYPE(S2), where S2 extends
S.

The program compiles with nagfor 5.2 and (reportedly) with the cray compiler,
but gfortran rejects the code with the error messages:

  Tobj = T(Sobj)
           1
Error: Can't convert TYPE(s) to CLASS(s) at (1)

  Tobj = T(S2obj)
           1
Error: Can't convert TYPE(s2) to CLASS(s) at (1)

===============

>From the F2008 standard:

"For a nonpointer component, the declared type and type parameters of the
component and expr shall conform in the same way as for a variable and expr in
an intrinsic assignment statement (7.2.1.2) [...]" (4.5.10p2)

"if the variable is polymorphic it shall be type compatible with expr; [...]"
(7.2.1.2p1(4))

Also 4.5.10 p6 applies to allocatable components.

===============

program main

  type :: S
    integer :: n
  end type
  type(S) :: Sobj

  type, extends(S) :: S2
    integer :: m
  end type
  type(S2) :: S2obj

  type :: T
    class(S), allocatable :: x
  end type
  type(T) :: Tobj

  Sobj = S(1)
  Tobj = T(Sobj)

  S2obj = S2(1,2)
  Tobj = T(S2obj)

end program