<<< mml $\text{Inline, auto, thick line }\genfrac{}{}{1pt}{}{x^2+1}{x}\text{, the superscripted 2 should be script-script size.}$ >>> native [ EText TextNormal "Inline, auto, thick line\160" , EFraction NormalFrac (EGrouped [ ESuper (EIdentifier "x") (ENumber "2") , ESymbol Bin "+" , ENumber "1" ]) (EIdentifier "x") , EText TextNormal ", the superscripted 2 should be script-script size." ]