+{- Note [ScrutOcc]
+
+An occurrence of ScrutOcc indicates that the thing is *only* taken apart or applied.
+
+ Functions, litersl: ScrutOcc emptyUFM
+ Data constructors: ScrutOcc subs,
+
+where (subs :: UniqFM [ArgOcc]) gives usage of the *pattern-bound* components,
+The domain of the UniqFM is the Unique of the data constructor
+
+The [ArgOcc] is the occurrences of the *pattern-bound* components
+of the data structure. E.g.
+ data T a = forall b. MkT a b (b->a)
+A pattern binds b, x::a, y::b, z::b->a, but not 'a'!
+
+-}