[Feature Request] Zeroed swizzle operators (e.g. float3.x__, float3._y_, float3.__z)

I'd find it handy to have zeroed swizzle operators that would let me do something like this:

float3 first = new float3(1f, 2f, 3f);
float3 second = new float3(7f, 8f, 9f);

float3 combined = first.x_z + second._y_; // == new float3(1f, 8f, 3f)

For me, this sometimes seems easier to understand at a glance than having something like:

float3 first = new float3(1f, 2f, 3f);
float3 second = new float3(7f, 8f, 9f);

float3 combined = new float3(first.x, second.y, first.z); // == new float3(1f, 8f, 3f)

Start by locating the float3 swizzle operator definitions and any related tests or generation entry points; the issue names no files. Check how patterns such as x_z and y should combine components, then consider the request complete when the demonstrated expressions produce the expected float3 values and the behavior is covered by tests.