Question

I’m using visual studio and I’ve tried every thing I could think of. but don’t know why this piece of code generates error, this is my code:

template <class A,class B> B returnArgtype(void (A::*)(B)) {return *new B;}

struct test
{
    void function(int);
    decltype(returnArgtype(&test::function)) x;
};

and it generates this error :

error C2784: 'A returnArgtype(void (__thiscall A::* )(B))' : could not deduce template argument for 'void (__thiscall A::* )(B)' from 'void (int)'

and I’m wondering it doesn’t generate that error when parameter x is initializing inside a function, something like this:

struct test
{
    void function(int)
    {
        decltype(returnArgtype(&test::function)) x;
    }
};

Answer 1

This is the same bug I linked to on your other question (please upvote it to make it more likely MS will spend time fixing it):

C++ compiler loses member-ness of pointer-to-member-function during template deduction, causes ICE

Then, look at @Ise Wistera’s answer which is much simpler and probably doesn’t cause this problem.

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Microsoft updated the bug report to say they’ve figured out a fix.