class Prism::InNode

def ===(other)

comparing the value of locations. Locations are checked only for presence.
Implements case-equality for the node. This is effectively == but without 
def ===(other)
  other.is_a?(InNode) &&
    (pattern === other.pattern) &&
    (statements === other.statements) &&
    (in_loc.nil? == other.in_loc.nil?) &&
    (then_loc.nil? == other.then_loc.nil?)
end