Add support for "not element of" operator (∉)

[Don-vip]

I'd like to write this validator rule:

/* Many misuses of building=hangar insteaf of building=barn because it's the same word in French */
*[building=hangar][!aeroway] ∉ *[aeroway] {
  throwWarning: tr("{0} not inside {1}", "{0.tag}", "{2.key}");
}

It's not possible yet, is it possible to add !∈ as a new spatial operator (negation of element of)?

[bastiK]

Does the following work?

*[building=hangar][!aeroway] ∈ *[aeroway] {
  set hangar_in_aeroway;
}
*[aeroway]!.hangar_in_aeroway {
  throwWarning: ...;
}

[Don-vip]

I don't know.. but it's quite ugly ;) By the way for consistency we should use ∉ (​U+2209)