[Flang][Assumed-rank] Missing diagnose on invalid assumed-rank actual argument

[DanielCChen]

Consider the following code:

subroutine sub(arg)
  character(*) :: arg(..)

  interface
   subroutine sub1(arg1) bind(c)
     character(1) :: arg1(2,4)
   end subroutine
  end interface

  call sub1(arg)                    ! Invalid
  call sub2(arg)                    ! Invalid
  contains
    subroutine sub2(arg2)
      character(*) :: arg2(10)
    end subroutine sub2
end subroutine

Both calls to sub1 and sub2 are invalid based on c840 in the standard
[8.5.8.7]

C840 An assumed-rank variable name shall not appear in a designator or expression except as an actual argument that corresponds to a dummy argument that is assumed-rank, the argument of the function C_LOC or C_SIZEOF from the intrinsic module ISO_C_BINDING (18.2), the first dummy argument of an intrinsic inquiry function, or the selector of a SELECT RANK statement.

I don't see this can be a reasonable extension. Even it is, it seems not documented.

[llvmbot]

@llvm/issue-subscribers-bug

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` subroutine sub(arg) character(*) :: arg(..)

interface
subroutine sub1(arg1) bind(c)
character(1) :: arg1(2,4)
end subroutine
end interface

call sub1(arg) ! Invalid
call sub2(arg) ! Invalid
contains
subroutine sub2(arg2)
character(*) :: arg2(10)
end subroutine sub2
end subroutine

Both calls to `sub1` and `sub2` are invalid based on `c840` in the standard
[8.5.8.7]

C840 An assumed-rank variable name shall not appear in a designator or expression except as an actual argument that corresponds to a dummy argument that is assumed-rank, the argument of the function C_LOC or C_SIZEOF from the intrinsic module ISO_C_BINDING (18.2), the first dummy argument of an intrinsic inquiry function, or the selector of a SELECT RANK statement.

I don't see this can be a reasonable extension. Even it is, it seems not documented.
</details>

[llvmbot]

@llvm/issue-subscribers-flang-frontend

Author: Daniel Chen (DanielCChen)

Consider the following code: ``` subroutine sub(arg) character(*) :: arg(..)

interface
subroutine sub1(arg1) bind(c)
character(1) :: arg1(2,4)
end subroutine
end interface

call sub1(arg) ! Invalid
call sub2(arg) ! Invalid
contains
subroutine sub2(arg2)
character(*) :: arg2(10)
end subroutine sub2
end subroutine

Both calls to `sub1` and `sub2` are invalid based on `c840` in the standard
[8.5.8.7]

C840 An assumed-rank variable name shall not appear in a designator or expression except as an actual argument that corresponds to a dummy argument that is assumed-rank, the argument of the function C_LOC or C_SIZEOF from the intrinsic module ISO_C_BINDING (18.2), the first dummy argument of an intrinsic inquiry function, or the selector of a SELECT RANK statement.

I don't see this can be a reasonable extension. Even it is, it seems not documented.
</details>

[klausler]

Passing an assumed-rank actual argument as a storage association (15.5.2.12) is an intentional extension supported by nvfortran. I'll add documentation and an optional portability warning.