"Crossing ways" operator in MapCSS

[naoliv]

Could we have some kind of "crossing ways" operator, please? (like #9516, but for ways)
For example:

way[waterway=river] ⤫ way[natural=tree_row] {
    throwWarning: tr("foo");
}

or even ways and relations:

way[highway] ⤫ relation[boundary=administrative] {
    throwWarning: tr("foo");
}

[anonymous]

This would be amazing, as it would essentially allow me and others to run "in-line" validation checks over an area I am working on.

[anonymous]

Is there someone working on this?

[GerdP]

See also #13165. It would be quite easy to implement a new operator that works for lines, not closed areas.