[Flang] Incorrect diagnostic on intrinsic `ASSOCIATED` when the `TARGET` argument is unlimited polymorphic

[DanielCChen]

Consider the following code

    type :: bType
        integer*4 :: i1
    end type

    type base
        type (bType), pointer :: b1
    end type

    class (*), allocatable, target :: x

    type (base) :: b1

    if (.not. associated (b1%b1, x)) error stop(2_4)
end

Flang currently issues an error as:

./t.f:13:15: error: Arguments of ASSOCIATED() must be a pointer and an optional valid target
      if (.not. associated (b1%b1, x)) error stop(2_4)
                ^^^^^^^^^^^^^^^^^^^^^

The code seems valid as the standard requires the type of TARGET to be compatible with POINTER argument.
Unlimited polymorphic entity is type compatible with all entities.

All ifort, gfortran and XLF compile the code successfully.

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Consider the following code ``` type :: bType integer*4 :: i1 end type

type base
    type (bType), pointer :: b1
end type

class (*), allocatable, target :: x

type (base) :: b1

if (.not. associated (b1%b1, x)) error stop(2_4)

end

Flang currently issues an error as:

./t.f:13:15: error: Arguments of ASSOCIATED() must be a pointer and an optional valid target
if (.not. associated (b1%b1, x)) error stop(2_4)
^^^^^^^^^^^^^^^^^^^^^

The code seems valid as the standard requires the type of `TARGET` to be compatible with `POINTER` argument.
Unlimited polymorphic entity is type compatible with all entities.

All ifort, gfortran and XLF compile the code successfully.
</details>

[klausler]

I think that this is a bug. 7.3.3 has "Even though an unlimited polymorphic entity is not considered to have a declared type, it is type compatible with all entities.", and the text defining ASSOCIATED only requires that the target be type compatible with the pointer in the case of a data pointer.

[klausler]

type t                                                                                                                                                          
end type                                                                                                                                                     
real, pointer :: rptr                                                                                                                                           
type(t), pointer :: tptr                                                                                                                                
class(*), pointer :: ulpp  
! nvfortran and cray emit no error for any of these                                                                                                                                     
print *, associated(rptr, ulpp) ! error with gfortran, ifx, nag; warning with xlf                                                                               
print *, associated(ulpp, rptr) ! error with ifx, nag; warning with xlf                                                                                         
print *, associated(tptr, ulpp) ! error with gfortran, nag; warning with xlf                                                                                    
print *, associated(ulpp, tptr) ! ok with all                                                                                                                   
print *, associated(rptr, tptr) ! not standard; error with gfortran, ifx, nag, warning with xlf                     
print *, associated(tptr, rptr) ! not standard; error with gfortran, ifx, nag, warning with xlf                                                               
end                                                                                                                                                             

I think that only the last two calls should be flagged as errors. I might emit a portability warning for the first three cases.