Roslyn: Expose IsByRefLikeType on INameTypeSymbol

[JohanLarsson]

Useful information that I don't know how to dig out using existing API.

[JohanLarsson]

Use case is in https://github.com/DotNetAnalyzers/ReflectionAnalyzers where we want to check:

typeof(C<>).MakeGenericType(typeof(RefStruct));

class C<T>
{
}

[CyrusNajmabadi]

That use case doesn't seem to have any ref-structs. Nor does it explain why it's important to know if it's a ref-struct.

[JohanLarsson]

The goal of the analyzer is to produce warnings when MakeGenericType is called with illegal type parameters that would be runtime errors. I just checked and this call does not throw at runtime so it is not a good example for motivation :)

[jnm2]

MakeGenericType does throw when called with Span<Foo>.