class RuboCop::Cop::Lint::DuplicateRegexpCharacterClassElement

that are within an interpolation.
mark every space (except the first) as duplicate if we do not skip regexp_parser nodes
Since we blank interpolations with a space for every char of the interpolation, we would

def within_interpolation?(node, child)
  parse_tree_child_loc = child.expression
  interpolation_locs(node).any? { |il| il.overlaps?(parse_tree_child_loc) }
end