Equivalent of C++ (nameless) union with nameless structs

[WarEagle451]

(C++)

template<typename T> struct vec4 { T x, y, z, w; };

struct color {
	union {
		vec4<float> data{ 0, 0, 0, 0};
		struct { float r, b, g, a };
	};
};

I understand that choice types are tagged unions, but there is no example or mention about how someone would implement the above code in Carbon. Also there is no mention of nameless unions. I would imagine it could be somewhat like below.

(Carbon)

class Vec4(template T:! Type) { var x: T; var y: T; var z: T; var w: T; };

class Color {
	choice {
		Data: Vec4(f32) = (.x = 0, .y = 0, .z = 0, .w = 0), // I hope this is correct
		struct { var R: f32; var G: f32; var B: f32; var A: f32; };
	};
};

While something like this isn't essential, the following points are why this should be added if it is not already;

• Cleaner code
• More readable code
• Interoperability with C++
• Straight forward to implement (As to write and understand)

Side note: Are you able to declare vars like var x, y, z, w: f32?

[geoffromer]

Carbon will very likely eventually have support for un-tagged unions, but there isn't a design yet. I proposed one in #139, but dropped it because there were some tricky design questions to resolve, and I figured out a way to get it off the critical path for tagged unions, which was my main priority at the time. If you or someone else wants to propose a design for un-tagged unions, that might be a good starting point, although some aspects of it are pretty outdated by now.

Side note: Are you able to declare vars like var x, y, z, w: f32?

No, although you can do var (x: f32, y: f32, z: f32, w: f32) = .... A name binding always consists of a single name, then a :, then a type expression.

[WarEagle451]

if you or someone else wants to propose a design for un-tagged unions

Thanks, I'll probably do that when I have time

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