\section[Desugar_intro]{Introduction}

This pass of the \Haskell{} compiler converts a typechecked program in
@AbsSyntax@ form into a list of @CoreBinding@s, a much simpler form
more suitable for subsequent passes.  The basic tasks in this
``desugaring'' are:
\begin{enumerate}
\item
Compile pattern-matching into equivalent code, mainly case-expressions.

\item
Convert list comprehensions into equivalent code.

\item
Make explicit all of the implicit activity due to overloading,
dictionaries, etc., etc.
\end{enumerate}

For the basic desugaring process, we assume familiarity with Phil
Wadler's chapter~5 in SLPJ.  The code here will be recognizable by the
avid reader of that chapter.  The main difference you will see is that
this code uses a simple monad to pass around the name supply; if
you've read much of this compiler's code, the idioms used will be
grievously familiar.