[Migrated] We should consider using `#[rustc_on_unimplemented]` on `spirv-std` helper traits.

Issue automatically imported from old repo: https://github.com/EmbarkStudios/rust-gpu/issues/983
Old labels: t: enhancement
Originally creatd by eddyb on 2023-01-05T12:44:08Z

I was reviewing this nightly bump PR:

• https://github.com/EmbarkStudios/rust-gpu/pull/982

And its diff shows some nightly diagnostic improvements of the form:

 12  |     *output = image.query_levels();
-    |               ^^^^^ ------------ required by a bound introduced by this call
-    |               |
-    |               the trait `HasQueryLevels` is not implemented for `Image<f32, 4, 2, 0, 0, 1, 0>`
+    |                     ^^^^^^^^^^^^ the trait `HasQueryLevels` is not implemented for `Image<f32, 4, 2, 0, 0, 1, 0>`
     |
     = help: the following other types implement trait `HasQueryLevels`:
               Image<SampledType, 0, DEPTH, ARRAYED, MULTISAMPLED, SAMPLED, FORMAT>

That's definitely better, but the trait can't really explain itself and its connection to the types (i.e. "Image types support query_levels only if such and such parameters have these values" etc.).

Except, in core/std, traits can and very much do do this, using #[rustc_on_unimplemented]!

It's perma-unstable, and there might be efforts to stabilize a subset of it, but even ignoring that, we can still use it under #[cfg_attr(target_arch = "spirv", ...)], just like all the other rustc internals we rely on.

Commencez par localiser les définitions des traits auxiliaires de spirv-std impliquées dans des méthodes telles que query_levels, puis examinez les changements apportés aux diagnostics de nightly dans la PR 982 ainsi que le comportement documenté de rustc_on_unimplemented. Le travail sera considéré comme terminé lorsque les combinaisons de paramètres Image non prises en charge produiront des diagnostics expliquant l’exigence de trait concernée et les combinaisons valides, tandis que l’attribut restera gated pour les cibles SPIR-V.