+Note [Cast then apply]
+~~~~~~~~~~~~~~~~~~~~~~
+Consider
+ myIndex = __inline_me ( (/\a. <blah>) |> co )
+ co :: (forall a. a -> a) ~ (forall a. T a)
+ ... /\a.\x. case ((myIndex a) |> sym co) x of { ... } ...
+
+We need to inline myIndex to unravel this; but the actual call (myIndex a) has
+no value arguments. The ValAppCtxt gives it enough incentive to inline.
+