C ++ 11 decltype和auto关键字 [英] C++11 decltype and auto keywords

问题描述

我要使用VC11构建以下内容

I have the following which I''m trying to build with VC11

struct Message 
{
	void Process();
};

struct Builder
{
	Message* Build() const {return new Message();}
};

template <typename BuilderT>
auto MakeAndReturn(const BuilderT& builder) -> decltype(BuilderT.Build())
{
	auto obj = builder.Build();

	return obj;
}

void Test()
{
	Builder builder;

	auto message = MakeAndReturn(builder);
}

但我从Test()的最后一行得到了此编译器错误

but I get this compiler error from the final line in Test()

1>y:\repo\cpp11\test\auto.cc(152): error C2893: Failed to specialize function template ''''unknown-type'' MakeAndReturn(const BuilderT &)''
1>          With the following template arguments:
1>          ''Builder''
1>y:\repo\cpp11\test\auto.cc(152): fatal error C1903: unable to recover from previous error(s); stopping compilation

谁能解释原因?

Can anyone explain why?

推荐答案

我发现了问题

I found the problem

auto MakeAndReturn(const BuilderT& builder) -> decltype(BuilderT.Build())

应该是

should be

auto MakeAndReturn(const BuilderT& builder) -> decltype(builder.Build())

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