<<< native
[ EArray
    [ AlignCenter ]
    [ [ [ EGrouped
            [ EPhantom (EText TextNormal "fail")
            , EIdentifier "H"
            , EPhantom (EText TextNormal "fail")
            ]
        ]
      ]
    , [ [ EIdentifier "T" ] ]
    , [ [ EIdentifier "U" ] ]
    ]
, ESymbol Rel "="
, EArray
    [ AlignCenter ]
    [ [ [ EIdentifier "H" ] ]
    , [ [ EIdentifier "T" ] ]
    , [ [ EGrouped
            [ EPhantom (EText TextNormal "fail")
            , EIdentifier "U"
            , EPhantom (EText TextNormal "fail")
            ]
        ]
      ]
    ]
]
>>> eqn
matrix{
ccol{ {hphantom {roman "fail"} H hphantom {roman "fail"}} above T above U }
} = matrix{
ccol{ H above T above {hphantom {roman "fail"} U hphantom {roman "fail"}} }
}