<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/139129>139129</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [flang] Semantic error on pure subroutine that compiles with gfortran and ifx
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            flang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          R-Goc
      </td>
    </tr>
</table>

<pre>
    Hitting this issue when trying to compile fortran-stdlib ([issue there](https://github.com/fortran-lang/stdlib/issues/990)). 
Other compilers accept this code. Compiling [stdlib-error.f90](https://github.com/fortran-lang/stdlib/blob/master/src/stdlib_error.fypp): 
```
error: Semantic errors in src/CMakeFiles/fortran_stdlib.dir/stdlib_error.f90-pp.f90
/code/rbfx-new/standalone/batched-assembly/stdlib/build/src/stdlib_error.f90:245:14: error: Left-hand side of assignment is not definable
               ierr_out = ierr
 ^^^^^^^^
/code/rbfx-new/standalone/batched-assembly/stdlib/build/src/stdlib_error.f90:245:14: because: 'ierr_out' is polymorphic in a pure subprogram
 ierr_out = ierr
 ^^^^^^^^
/code/rbfx-new/standalone/batched-assembly/stdlib/build/src/stdlib_error.f90:239:56: Declaration of 'ierr_out'
           class(state_type), optional, intent(inout) :: ierr_out
 ^^^^^^^^
```
This is the [function](https://github.com/fortran-lang/stdlib/blob/c14d599a7b9dabf8789be6ecc484339599f595c8/src/stdlib_error.fypp#L239):
```fortran
 pure subroutine error_handling(ierr,ierr_out)
         class(state_type), intent(in) :: ierr
         class(state_type), optional, intent(inout) :: ierr_out

         character(len=:),allocatable :: err_msg

         if (present(ierr_out)) then
             ! Return error flag
 ierr_out = ierr
         elseif (ierr%error()) then
             err_msg = ierr%print()
             error stop err_msg
         end if

    end subroutine error_handling
```
[state_type](https://github.com/fortran-lang/stdlib/blob/c14d599a7b9dabf8789be6ecc484339599f595c8/src/stdlib_error.fypp#L52):
```fortran
 type :: state_type

        !> The current exit state
 integer(ilp) :: state = STDLIB_SUCCESS

        !> Message associated to the current state
        character(len=MSG_LENGTH) :: message = repeat(' ',MSG_LENGTH)

        !> Location of the state change
 character(len=NAME_LENGTH) :: where_at = repeat(' ',NAME_LENGTH)

 contains

           !> Cleanup
           procedure :: destroy   => state_destroy
           
           !> Parse error constructor
 procedure, private :: state_parse_at_location
           procedure, private :: state_parse_arguments
           generic   :: parse     => state_parse_at_location, &
 state_parse_arguments

           !> Print error message
 procedure :: print     => state_print
           procedure :: print_msg => state_message

           !> State properties
           procedure :: ok => state_is_ok
           procedure :: error     => state_is_error
 
           !> Handle optional error message 
           procedure :: handle    => error_handling

    end type state_type
```
state_type is also extended by two methods:
```fortran
    interface state_type
 module procedure new_state
        module procedure new_state_nowhere
 end interface state_type
```
which are defined [here](https://github.com/fortran-lang/stdlib/blob/c14d599a7b9dabf8789be6ecc484339599f595c8/src/stdlib_error.fypp#L513):
```fortran
 pure type(state_type) function new_state(where_at,flag,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10, &
 a11,a12,a13,a14,a15,a16,a17,a18,a19,a20) 

 !> Location
       character(len=*),intent(in) :: where_at

       !> Input error flag
       integer,intent(in) :: flag

       !> Optional rank-agnostic arguments
       class(*),optional,intent(in),dimension(..) :: a1,a2,a3,a4,a5,a6,a7,a8,a9,a10, &
 a11,a12,a13,a14,a15,a16,a17,a18,a19,a20  

       ! Init object
 call new_state%parse(where_at,flag,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10, &
 a11,a12,a13,a14,a15,a16,a17,a18,a19,a20)

    end function new_state

    !> Error creation message, from N input variables (numeric or strings)
    pure type(state_type) function new_state_nowhere(flag,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10, &
 a11,a12,a13,a14,a15,a16,a17,a18,a19,a20) &
 result(new_state)

 !> Input error flag
       integer,intent(in) :: flag

       !> Optional rank-agnostic arguments
 class(*),optional,intent(in),dimension(..) :: a1,a2,a3,a4,a5,a6,a7,a8,a9,a10, &
 a11,a12,a13,a14,a15,a16,a17,a18,a19,a20  

       ! Init object
 call new_state%parse(flag,a1,a2,a3,a4,a5,a6,a7,a8,a9,a10, &
 a11,a12,a13,a14,a15,a16,a17,a18,a19,a20)

    end function new_state_nowhere
```

</pre>
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