message: ENH: use constexpr for mpi_traits
diff: @@ -69,10 +69,10 @@ using IndexType = int32;
  /*!
  * \brief Traits class to map Axom types to their corresponding MPI type.
  */
  -template < typename AxomType >
  +template < class AxomType >
  struct mpi_traits
  {
  - static const MPI_Datatype type = MPI_DATATYPE_NULL;
  + static constexpr MPI_Datatype type = MPI_DATATYPE_NULL;
  };
  /// \name Specialization of mpi_traits
  @@ -82,28 +82,28 @@ struct mpi_traits
  template < >
  struct mpi_traits < float64 >
  {
  - static const MPI_Datatype type = MPI_DOUBLE;
  + static constexpr MPI_Datatype type = MPI_DOUBLE;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < float32 >
  {
  - static const MPI_Datatype type = MPI_FLOAT;
  + static constexpr MPI_Datatype type = MPI_FLOAT;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < int8 >
  {
  - static const MPI_Datatype type = MPI_INT8_T;
  + static constexpr MPI_Datatype type = MPI_INT8_T;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < uint8 >
  {
  - static const MPI_Datatype type = MPI_UINT8_T;
  + static constexpr MPI_Datatype type = MPI_UINT8_T;
  };
  @@ -111,28 +111,28 @@ struct mpi_traits < uint8 >
  template < >
  struct mpi_traits < int16 >
  {
  - static const MPI_Datatype type = MPI_INT16_T;
  + static constexpr MPI_Datatype type = MPI_INT16_T;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < uint16 >
  {
  - static const MPI_Datatype type = MPI_UINT16_T;
  + static constexpr MPI_Datatype type = MPI_UINT16_T;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < int32 >
  {
  - static const MPI_Datatype type = MPI_INT32_T;
  + static constexpr MPI_Datatype type = MPI_INT32_T;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < uint32 >
  {
  - static const MPI_Datatype type = MPI_UINT32_T;
  + static constexpr MPI_Datatype type = MPI_UINT32_T;
  };
  //------------------------------------------------------------------------------
  @@ -140,14 +140,14 @@ struct mpi_traits < uint32 >
  template < >
  struct mpi_traits < int64 >
  {
  - static const MPI_Datatype type = MPI_INT64_T;
  + static constexpr MPI_Datatype type = MPI_INT64_T;
  };
  //------------------------------------------------------------------------------
  template < >
  struct mpi_traits < uint64 >
  {
  - static const MPI_Datatype type = MPI_UINT64_T;
  + static constexpr MPI_Datatype type = MPI_UINT64_T;
  };
  #endif /* end AXOM_NO_INT64_T */
  