I tried the following :

#include <boost/spirit/core.hpp>
#include <boost/spirit/utility/grammar_def.hpp> 

namespace spirit = boost::spirit;

struct Test : public spirit::grammar<Test>
{
  template <typename ScannerT>
  struct definition : public spirit::grammar_def<spirit::rule<ScannerT>,
spirit::same>
  {
    definition(Test const& self)
    {
      a = spirit::ch_p('a');
      b = spirit::ch_p('b');

      this->start_parsers(a, b);
    }

    spirit::rule<ScannerT> a, b;
  };
};

struct TestWrap : public spirit::grammar<TestWrap>
{
  template <typename ScannerT>
  struct definition
  {
    definition(TestWrap const& self)
    {
      b = test.use_parser<1>();
    }

    spirit::rule<ScannerT> const& start() const { return b; }

    Test test;
    spirit::rule<ScannerT> b;
  };
};

int __cdecl main()
{
  TestWrap testWrap;

  parse( "a", testWrap, spirit::blank_p );
}

and I get the following error

K:\Work\boost_1_32_0\boost\spirit\core\non_terminal\impl\rule.ipp(227):
error C2440: 'initializing' : 
cannot convert from 'const boost::spirit::impl::entry_grammar<Test, 1,
boost::spirit::parser_context<> >'
to 'boost::spirit::impl::entry_grammar<Test, 1,
boost::spirit::parser_context<> >::embed_t'

Is that a bug ?

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