+
+Note [Desugaring RULE left hand sides]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+For the LHS of a RULE we do *not* want to desugar
+ [x] to build (\cn. x `c` n)
+We want to leave explicit lists simply as chains
+of cons's. We can achieve that slightly indirectly by
+switching off EnableRewriteRules. See DsExpr.dsExplicitList.
+
+That keeps the desugaring of list comprehensions simple too.