class Prism::PinnedExpressionNode

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?(PinnedExpressionNode) &&
    (expression === other.expression) &&
    (operator_loc.nil? == other.operator_loc.nil?) &&
    (lparen_loc.nil? == other.lparen_loc.nil?) &&
    (rparen_loc.nil? == other.rparen_loc.nil?)
end