Fix minor typo in generics stuff; could merge with branch
any operator starting in a colon as an infix type constructor). Also note that
the type constructors are not exactly as in the paper (Unit instead of 1, etc).
Finally, note that the syntax of the type patterns in the class declaration
-uses "<literal>{|</literal>" and "<literal>{|</literal>" brackets; curly braces
+uses "<literal>{|</literal>" and "<literal>|}</literal>" brackets; curly braces
alone would ambiguous when they appear on right hand sides (an extension we
anticipate wanting).
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