texmath-0.12.5: test/roundtrip/mfrac7.native

[ EFraction
    NormalFrac
    (EGrouped
       [ EIdentifier "x"
       , ESymbol Bin "+"
       , EIdentifier "y"
       , ESymbol Bin "+"
       , EIdentifier "z"
       ])
    (EGrouped
       [ EIdentifier "x"
       , EPhantom (ESymbol Bin "+")
       , EPhantom (EIdentifier "y")
       , ESymbol Bin "+"
       , EIdentifier "z"
       ])
]