[typetraits.inl] msvc __is_aggregate error

[Crydsch]

I noticed a little compiler issue with msvc and the __is_aggregate function.
For some reason it generates a C2760 Error
syntax error: '__is_aggregate' was unexpected here; expected 'expression' typetraits.inl 165

I am not sure what happens here, maybe not supported, may be a compiler bug.
Anyway, I am not using any typetraits, but since it is included by bx.h the compiler complains.

For now I fixed it by removing the entire function.
I am using VS2022 with C++20. I you need any other information please let me know.

[Crydsch]

A little testing reveals a simple fix:

template<typename Ty>
inline constexpr bool isAggregate()
{
	return !!__is_aggregate(Ty);
}

Not sure why, but that seems to fix it. I guess it is bug after all.

A few quick tests confirm that the function can detect aggregate types correctly.
That being said, I am not very well versed with this typetrait stuff..

[bkaradzic]

I noticed a little compiler issue with msvc and the __is_aggregate function.

You get this compiler error without instantiating template?

[bkaradzic]

Can you reproduce the issue on compiler explorer?
https://godbolt.org/z/986fraTdj

I just tried it and not getting any issue with different versions of MSVC compiler.

[Crydsch]

So i can reproduce it from msvc v19.30 onwards (i am on latest).
Interestingly only with C++20 enabled.
https://godbolt.org/z/KWYh9888W

Perhaps it got deprecated?
It works with

template<typename Ty>
inline constexpr bool isAggregate()
{
    const bool res = __is_aggregate(Ty);
    return res;
}

Also, Instantiation is not necessary just code generation in general.
Apparently the compiler will generate template functions, even if not in use...

[bkaradzic]

Yeah, your fix with !! is fine, no need to change, I just want to understand the issue, and then do fix.
I also noticed __is_aggregate changes behavior depending on C++ standard set. For example I tested between 14 vs 17.

[Crydsch]

Works like charm now. Thanks :)