[GSoC] Compiler support for invocation_type

[Fan You]

Hi,

I'm working on implementing invocation_type
<http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2014/n3866.html>

However, I find it hard to get the matched invocation parameter of
function F by specialization and SFINAE.

For example:

int f(const char*);
int f(int);

How can I get the invocation parameter of INVOKE(f, "abc")? which
should be (const char*).

I saw invocation_type is a compiler-supported type, but I don't know
how to make use of the compiler to achieve this.

-- 
Regards,

Fan