64 b and array Fragment output

doubles ant longs cannot be written as color attachment directly:

Output values written by a fragment shader must be declared with either OpTypeFloat or OpTypeInt, and a Width of 32.

Even if the device otherwisely supports them. I assume because vec3 and vec4 would take two Location, which would prevent interfacing with color attachments:

Locations are consumed as described in Location Assignment.

A fragment shader output variable identified with a Location decoration of i is directed to the color attachment indicated by pColorAttachments[i],

Each element of the pColorAttachments array corresponds to an output location in the shader, i.e. if the shader declares an output variable decorated with a Location value of X, then it uses the attachment provided in pColorAttachments[X].

But that feels like API defect; perhaps some extension should figure some healthy way around this?

Not sure how array image color attachments would work. They do not seem to be forbidden in VU at vkCreateFramebuffer, but they would take N Locations. But at the same time the spec requires that Location and pColorAttachment index matches. Are array attachments allowed?

Start by reading the cited Vulkan rules for fragment shader output types, Location Assignment, color attachments, and framebuffer creation. Determine how 64-bit outputs and array image attachments are specified, then document or clarify the intended behavior; completion requires a resolved specification answer rather than an implementation alone.