Note that \lam{x0} and {x1} will still need normalization after this.
\subsubsection{Argument propagation}
+ TODO: Generalize this section into specialization, so other
+ transformations can refer to this (since specialization is really used
+ in multiple categories).
+
This transform deals with arguments to user-defined functions that are
not representable at runtime. This means these arguments cannot be
preserved in the final form and most be {\em propagated}.