Should accessor::operator[](id<Dim>) only be available for Dim > 1?

[illuhad]

Currently, we have accessor::operator[](id<Dim>) available for device accessors if Dim > 0: https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#_interface_for_buffer_command_accessors

I believe this can cause ambiguities if accessor::operator[] is used with item<1> as argument instead of id<1>:

• item<1> can be implicitly converted to id<1>, for which an accessor::operator[] overload exists
• item<1> can be implicitly converted to size_t, for which an accessor::operator[] overload exists as well.

Do we want to support passing item to accessor::operator[]? If so, I think one solution could be to make the accessor::operator[](id<Dim>) only available for Dim > 1. This is how I have solved this at the moment.

Passing id<1> still works, because then id<1> would be implicitly converted to size_t, and then accessor::operator[](size_t) can be used.

I'm curious how other implementers have solved this, because going strictly by the synopsis as defined in the spec will not work I think.

[gmlueck]

item<1> can be implicitly converted to id<1>

Is this true? I don't see this in the spec.

[illuhad]

id has non-explicit constructor accepting item: https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#id-class

[tomdeakin]

22/11/24: more investigation required by implementors.