Support for methods in union types

[Jose E. Marchesi]

Hi peoples!

Just a FYI.  This morning I pushed support for having methods in union
types.

Methods are particularly useful in unions, for both pretty-printing and
getters/setters.

Example:

deftype Dwarf_Initial_Length =
  union
  {
    struct
    {
      uint<32> marker : (marker == 0xffffffff
                         && dwarf_set_bits (64));
      offset<uint<64>,B> length;
    } l64;

    offset<uint<32>,B> l32 : (l32 < 0xfffffff0#B
                              && dwarf_set_bits (32));

    method get_value = offset<uint<64>,B>:
      {
        try return l32;
        catch if E_elem { return l64.length; }
      }
  
    method _print = void:
      {
        print ("#<");
        try printf ("%v", l64.length);
        catch if E_elem { printf ("%v", l32); }
        print (">");
      }
  };

[...]

/* Compilation unit header.  */

deftype Dwarf_CU_Header =
  struct
  {
    /* Length of the .debug_info contribution for this CU, not
       including the length field itself.  */
    Dwarf_Initial_Length unit_length;

    /* Version of the DWARF information for the compilation unit.  */
    uint<16> version : (version in [2, 3, 4, 5]
                        && dwarf_set_version (version));

    /* Offset into the .debug_abbrev section that associates the
       compilation unit with a particular set of debugging information
       entry abbreviations.  */
    Dwarf_Section_Offset debug_abbrev_offset;

    /* Size of an address on the target architecture.  */
    offset<uint<8>,B> address_size;
  };


Session:

(poke) .file foo.o
[elf](poke) $elf::debug_info
Dwarf_CU_Header {
  unit_length=#<0x4bU#B>,
  version=0x4UH,
  debug_abbrev_offset=#<0x0U#B>,
  address_size=0x8UB#B
}
[elf](poke) $elf::debug_info.unit_length.get_value
0x4bUL#B