class SyntaxTree::Parser

def on_mrhs_add(mrhs, part)

on_mrhs_add: (MRHS mrhs, untyped part) -> MRHS
:call-seq: 
def on_mrhs_add(mrhs, part)
  location =
    (mrhs.parts.empty? ? mrhs.location : mrhs.location.to(part.location))
  MRHS.new(parts: mrhs.parts << part, location: location)
end