These are now autodetected.
\starttrans
x = E
~
-x Y0 ... Yi ... Yn \lam{Y_i} is not of a runtime representable type
---------------------------------------------- \lam{Y_i} is not a local variable reference
+x Y0 ... Yi ... Yn \lam{Yi} is not of a runtime representable type
+--------------------------------------------- \lam{Yi} is not a local variable reference
x' = λy0 ... yi-1 f0 ... fm yi+1 ... yn . \lam{f0 ... fm} = free local vars of \lam{Y_i}
E y0 ... yi-1 Yi yi+1 ... yn
~