如果我编写此代码，它仍会编译：
namespace MyNamespace
{
struct STreeConstructionRuleQuery : std::string {};
struct STreeConstructionRuleOperation : std::string {};
struct STreeConstructionRuleOperand : std::string {};
struct STreeConstructionRuleCondition : std::string {};
struct STreeConstructionRuleOperationWithOperands : boost::tuple<STreeConstructionRuleOperation, std::vector<STreeConstructionRuleOperand> > {};
struct STreeConstructionRule
{
boost::optional<std::vector<std::vector<STreeConstructionRuleOperationWithOperands> > > m_sAssertion;
STreeConstructionRuleQuery m_sQuery;
STreeConstructionRuleOperationWithOperands m_sAction;
boost::optional<STreeConstructionRuleCondition> m_sCondition;
};
}
BOOST_FUSION_ADAPT_STRUCT(
MyNamespace::STreeConstructionRule,
(boost::optional<std::vector<std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> > >, m_sAssertion)
(MyNamespace::STreeConstructionRuleQuery, m_sQuery)
(MyNamespace::STreeConstructionRuleOperationWithOperands, m_sAction)
(boost::optional<MyNamespace::STreeConstructionRuleCondition>, m_sCondition)
)
namespace MyNamespace
{
namespace qi = boost::spirit::qi;
namespace ascii = boost::spirit::ascii;
namespace phoenix = boost::phoenix;
template <typename Iterator>
struct STreeContructionRulesGrammar : qi::grammar<Iterator, std::vector<STreeConstructionRule>(), ascii::space_type>
{
qi::rule<Iterator, std::vector<STreeConstructionRule>(), ascii::space_type> m_oStart;
qi::rule<Iterator, qi::unused_type(), ascii::space_type> m_oComment;
qi::rule<Iterator, STreeConstructionRule(), ascii::space_type> m_oRule;
STreeContructionRulesGrammar() : STreeContructionRulesGrammar::base_type(m_oStart)
{
m_oStart = *(m_oComment | m_oRule [phoenix::push_back(qi::_val, qi::_1)]);
m_oComment = (("-->" >> *(qi::char_) >> "<--") | ('#' >> *(qi::char_ - qi::char_("\n\r"))));
}
};
}
但是当我将STreeConstructionRuleOperand的定义更改为
struct STreeConstructionRuleOperand : boost::variant<int> {};
我收到以下编译错误（使用STLPort代替STL）：
1>d:\commonlib\include\boost\variant\variant.hpp(1373) : error C2666: 'boost::variant<T0_>::convert_construct' : 2 overloads have similar conversions
1> with
1> [
1> T0_=int
1> ]
1> d:\commonlib\include\boost\variant\variant.hpp(1358): could be 'void boost::variant<T0_>::convert_construct<int,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_,boost::detail::variant::void_>(const boost::variant<T0_> &,long)'
1> with
1> [
1> T0_=int
1> ]
1> d:\commonlib\include\boost\variant\variant.hpp(1289): or 'void boost::variant<T0_>::convert_construct<const T>(T &,int,boost::mpl::false_)'
1> with
1> [
1> T0_=int,
1> T=MyNamespace::STreeConstructionRuleOperand
1> ]
1> while trying to match the argument list '(const MyNamespace::STreeConstructionRuleOperand, long)'
1> d:\commonlib\include\boost\fusion\container\vector\detail\vector_n.hpp(45) : see reference to function template instantiation 'boost::variant<T0_>::variant<MyNamespace::STreeConstructionRuleOperand>(const T &)' being compiled
1> with
1> [
1> T0_=int,
1> T=MyNamespace::STreeConstructionRuleOperand
1> ]
1> d:\commonlib\include\stlport\stl\_uninitialized.h(93) : see reference to function template instantiation 'void stlpd_std::_Destroy_Range<_OutputIter>(_ForwardIterator,_ForwardIterator)' being compiled
1> with
1> [
1> _OutputIter=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *,
1> _ForwardIterator=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *
1> ]
1> d:\commonlib\include\stlport\stl\_uninitialized.h(113) : see reference to function template instantiation '_OutputIter stlpd_std::priv::__ucopy<_InputIter,_OutputIter,ptrdiff_t>(_RandomAccessIter,_RandomAccessIter,_OutputIter,const stlpd_std::random_access_iterator_tag &,_Distance *)' being compiled
1> with
1> [
1> _OutputIter=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *,
1> _InputIter=const stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *,
1> _RandomAccessIter=const stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *,
1> _Distance=ptrdiff_t
1> ]
1> d:\commonlib\include\stlport\stl\_vector.h(249) : see reference to function template instantiation '_OutputIter stlpd_std::priv::__ucopy_ptrs<const stlpd_std::vector<_Tp>*,stlpd_std::vector<_Tp>*>(_InputIter,_InputIter,_OutputIter,const stlpd_std::__false_type &)' being compiled
1> with
1> [
1> _OutputIter=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *,
1> _Tp=MyNamespace::STreeConstructionRuleOperationWithOperands,
1> _InputIter=const stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands> *
1> ]
1> d:\commonlib\include\stlport\stl\_vector.h(246) : while compiling class template member function 'stlpd_std::priv::_NonDbg_vector<_Tp,_Alloc>::_NonDbg_vector(const stlpd_std::priv::_NonDbg_vector<_Tp,_Alloc> &)'
1> with
1> [
1> _Tp=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>,
1> _Alloc=stlpd_std::allocator<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>
1> ]
1> d:\commonlib\include\stlport\stl\debug\_iterator.h(378) : see reference to class template instantiation 'stlpd_std::priv::_NonDbg_vector<_Tp,_Alloc>' being compiled
1> with
1> [
1> _Tp=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>,
1> _Alloc=stlpd_std::allocator<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>
1> ]
1> d:\commonlib\include\stlport\stl\debug\_vector.h(106) : see reference to class template instantiation 'stlpd_std::priv::__construct_checker<_Container>' being compiled
1> with
1> [
1> _Container=stlpd_std::priv::_NonDbg_vector<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>,stlpd_std::allocator<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>>
1> ]
1> d:\commonlib\include\boost\optional\optional.hpp(110) : see reference to class template instantiation 'stlpd_std::vector<_Tp>' being compiled
1> with
1> [
1> _Tp=stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>
1> ]
1> d:\commonlib\include\boost\optional\optional.hpp(113) : see reference to class template instantiation 'boost::optional_detail::aligned_storage<T>::dummy_u' being compiled
1> with
1> [
1> T=stlpd_std::vector<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>
1> ]
1> d:\commonlib\include\boost\optional\optional.hpp(450) : see reference to class template instantiation 'boost::optional_detail::aligned_storage<T>' being compiled
1> with
1> [
1> T=stlpd_std::vector<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>
1> ]
1> d:\commonlib\include\boost\optional\optional.hpp(457) : see reference to class template instantiation 'boost::optional_detail::optional_base<T>' being compiled
1> with
1> [
1> T=stlpd_std::vector<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>
1> ]
1> d:\preformator\sources\prefcore\preftreeconstructor.cpp(52) : see reference to class template instantiation 'boost::optional<T>' being compiled
1> with
1> [
1> T=stlpd_std::vector<stlpd_std::vector<MyNamespace::STreeConstructionRuleOperationWithOperands>>
1> ]
这是编译器报告的唯一错误。我没有看到任何歧义，但编译器确实如此。这个错误的原因是什么以及应该如何修复？
答案 0 :(得分：1)
这里有两件事让我感动：
以前的某些内容std::string将如何分配给现在为variant<int>的内容？
显示的代码不包含可解释此代码的代码（因为它可能在m_oRule或其中的子规则）。但也许variant<std::string>可以减少问题，看看你之前如何分配std::string值。
您似乎滥用 struct 继承以实现typedef行为。请注意，公共继承不与typedef相同，尤其是关于构造函数（不继承）。
尝试替换
的每次使用struct A : baseType {};
更常见的成语
typedef baseType A;
我实际上期望后者解决问题，因为你遇到构造函数过载问题。
无论如何，我只测试了gcc，boost_1_51_0和GNU libstdc ++。它会毫不费力地编译您发布的所有内容（但同样，您不会遗漏关键元素，例如规则 m_oRule，它会对RuleOpWithOperands进行实际分配。
使用继承代替typedef演示相关问题（至少一个）：
struct Type {
Type(int, double) { }
};
typedef Type ProperTypedef;
struct FauxTypedef : Type { };
int main()
{
Type a(1, 4.2); // okay
ProperTypedef b(1, 4.2); // okay as well, obviously
FauxTypedef c(1, 4.2); // oops ouch!!! This won't compile
}
如果您坚持使用_unique typeid作为typedef-ed名称，则可以使用BOOST_STRONG_TYPEDEF