If you are willing to use macros anyway, you can make the following work in C++ today:

   foo($(bar)=10, $(baz)="hello");

In fact you could 10 years ago when I implemented it[1]; in fact it allows significantly more than just named arguments (named tuples!), but please, consider it as some sort of art and not really something that should be anywhere close to production.

[1] https://github.com/gpderetta/libtask/blob/a5e6e16ddc4e00d9f7...