In reply to @solitudesf "then do it, idk.": What I mentioned
I call
``proc `[]=`(pal: ppal.Palette; index: SomeInteger, color: Color)`` which calls
``proc `[]=`[T](span: Span[T]; idx: SomeInteger, value: T)``
And it errors at ``span.data.toOpenArray(0, span.length)[idx] = T``