[英]Compilation error on ambiguous type in code using boost::spirit
If I write this code it still compiles: 如果我编写这段代码,它仍然可以编译:
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"))));
}
};
}
But when I change the definition of STreeConstructionRuleOperand
to 但是当我将
STreeConstructionRuleOperand
的定义STreeConstructionRuleOperand
为
struct STreeConstructionRuleOperand : boost::variant<int> {};
I get the following compilation error (STLPort is used instead of STL): 我收到以下编译错误(使用STLPort而不是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> ]
This is the only error the compiler reports. 这是编译器报告的唯一错误。 I don't see any ambiguity but the compiler does.
我看不出有任何歧义,但是编译器确实有。 What is the reason for this error and how it should be fixed?
此错误的原因是什么,应如何解决?
Two things strike me here: 这里有两点让我震惊:
how would something that is used to be std::string
, be assigned to something that is a now a variant<int>
? 如何将过去是
std::string
东西分配给现在为variant<int>
?
The code shown doesn't include the code that would explain this (as it is probably in m_oRule
or a subrule of that). 显示的代码不包含解释此问题的代码(因为它可能在
m_oRule
或它的子规则中)。 But perhaps a variant<std::string>
poses fewer problems, seeing how you had a std::string
value to assign before. 但是,也许
variant<std::string>
带来更少的问题,看看您之前如何分配std::string
值。
You appear to abuse struct
inheritance quite a lot to achieve typedef
behaviour. 您似乎非常滥用
struct
继承来实现typedef
行为。 Note that public inheritance is not the same as a typedef
, especially with regards to the constructors (which are not inherited). 需要注意的是公有继承是不一样的
typedef
,尤其是关于构造函数 ( 没有继承)。
Try replacing each use of 尝试替换每次使用
struct A : baseType {};
by the more usual idiom of 通过更常见的成语
typedef baseType A;
I actually expect the latter to solve the issue, since you are running into constructor overload trouble. 我实际上希望后者能够解决问题,因为您遇到了构造函数重载的麻烦。
Regardless of that, I have only tested with gcc, boost_1_51_0 and GNU libstdc++. 无论如何,我仅使用gcc,boost_1_51_0和GNU libstdc ++进行了测试。 It compiles everything you posted without a hitch (but again, not you left out crucial elements, such as the rule
m_oRule
that does the actual assigning to RuleOpWithOperands
). 它可以轻松编译您发布的所有内容(但同样,您也可以保留重要的元素,例如规则
m_oRule
,该元素实际分配给RuleOpWithOperands
)。
Demonstrating the relevant problem (at least one) with inheritance instead of typedef
: 用继承而不是
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
}
If you insist on having a _unique typeid
for the typedef-ed name, you can resort to BOOST_STRONG_TYPEDEF 如果您坚持使用_unique
typeid
作为类型定义名称,则可以使用BOOST_STRONG_TYPEDEF
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