Identifies whether a registered ALTREP class claims `x`. This is a class-membership question answered without touching the vector's data: it never materializes `x` and reports a match even when the class reader would decline to serve this particular instance (for example, a materialized `charvec`).
Value
`"package::class"` for a registered class match when class metadata is available; otherwise `NA_character_`.
Examples
charport_class_of(charvec("a"))
#> [1] "charport::charvec"
charport_class_of(letters)
#> [1] NA