Possible bug in Intel Fortran with GENERIC OPERATOR extension?

This is based on an ongoing discussion at the comp.lang.fortran forum (https://groups.google.com/forum/#!topic/comp.lang.fortran/aFNK3FXqTUA) on generic operator bindings to specific type-bound procedures and their extensions with extended derived type.  The simple code shown below is based on the postings in that thread as well as a companion thread at the gfortran gnu website.  This code appears alright with respect to the latest Fortran standard and it compiles and executes as expected using gfortran 4.9.  However, Intel Fortran compiler 15 raises an error which seems to be incorrect.

MODULE m

   !..
   IMPLICIT NONE

   !..
   PRIVATE

   TYPE, PUBLIC :: A_t

      !..
      PRIVATE

      !..
      INTEGER :: m_i = 0

   CONTAINS

      !..
      PRIVATE

      !..
      PROCEDURE, PASS(This) :: A_sum => sum_i

      !..
      GENERIC, PUBLIC :: OPERATOR(+) => A_sum

   END TYPE A_t

   TYPE, EXTENDS(A_t), PUBLIC ::  C_t

      !..
      PRIVATE

      !..
      REAL :: m_r = 1.0

   CONTAINS

      !..
      PROCEDURE, PASS(This) :: A_sum => sum_r
      PROCEDURE, PASS(This) :: C_sum => sum_s

      !..
      GENERIC, PUBLIC :: OPERATOR(+) => C_sum

   END TYPE C_t

   TYPE, PUBLIC :: S_t

      !..
      PRIVATE

      !..
      CHARACTER(LEN=6) :: m_s = "Hello!"

   END TYPE S_t

CONTAINS

   FUNCTION sum_i(This, Rhs) RESULT(RetVal)

      !.. Argument list
      CLASS(A_t), INTENT(IN) :: This
      INTEGER, INTENT(IN)    :: Rhs
      !.. Function result
      INTEGER :: RetVal

      RetVal = This%m_i + Rhs

      WRITE(*,*) 'In sum_i'

      !..
      RETURN

   END FUNCTION sum_i

   FUNCTION sum_r(This, Rhs) RESULT(RetVal)

      !.. Argument list
      CLASS(C_t), INTENT(IN) :: This
      INTEGER, INTENT(IN)    :: Rhs
      !.. Function result
      INTEGER :: RetVal

      RetVal = INT(This%m_r, KIND=KIND(RetVal)) + Rhs

      WRITE(*,*) 'In sum_r'

      !..
      RETURN

   END FUNCTION sum_r

   FUNCTION sum_s(This, Rhs) RESULT(RetVal)

      !.. Argument list
      CLASS(C_t), INTENT(IN) :: This
      CLASS(S_t), INTENT(IN) :: Rhs
      !.. Function result
      CHARACTER(LEN=6) :: RetVal

      !..
      IF (This%m_i == 0) THEN
         RetVal = Rhs%m_s
      END IF

      WRITE(*,*) 'In sum_s'

      !..
      RETURN

   END FUNCTION sum_s

END MODULE m

PROGRAM p

   USE m, ONLY : A_t, C_t, S_t

   IMPLICIT NONE

   !.. Local variables
   TYPE(A_t) :: A
   TYPE(C_t) :: C
   TYPE(S_t) :: S
   INTEGER :: I
   CHARACTER(LEN=6) :: G

   !..
   PRINT *, " Test #59: Generic Operator Extension "
   !..
   I = A + 1
   PRINT *, " I = ", I

   !..
   I = C + 1
   PRINT *, " I = ", I

   !..
   G = C + S
   PRINT *, " G = ", G

   !..
   STOP

END PROGRAM p

The compiler error is as follows:

1>Compiling with Intel(R) Visual Fortran Compiler XE 15.0.0.108 [Intel(R) 64]...
1>TestFor.f90
1>TestFor.f90(21): error #6355: This binary operation is invalid for this data type.   [C]
1>TestFor.f90(21): error #6549: An arithmetic or LOGICAL type is required in this context.
1>TestFor.f90(21): warning #6191: Fortran 2008 requires an arithmetic data type in this context.
1>TestFor.f90(21): error #6303: The assignment operation or the binary expression operation is invalid for the data types of the two operands.
1>compilation aborted for TestFor.f90 (code 1)

Note there is also another issue with Intel Fortran compiler giving an incorrect result if line 45 in module m i.e., if the generic operator + binding extension to another specific type-bound procedure is removed.  This is part of the question at the comp.lang.fortran thread.