class SyntaxTree::Parser

def on_xstring_add(xstring, part)

) -> XString
(StringEmbExpr | StringDVar | TStringContent) part
XString xstring,
on_xstring_add: (
:call-seq:
def on_xstring_add(xstring, part)
  XString.new(
    parts: xstring.parts << part,
    location: xstring.location.to(part.location)
  )
end