+Note [Dictionary binders in ConPatOut]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Do *not* gather (a) dictionary and (b) dictionary bindings as binders
+of a ConPatOut pattern. For most calls it doesn't matter, because
+it's pre-typechecker and there are no ConPatOuts. But it does matter
+more in the desugarer; for example, DsUtils.mkSelectorBinds uses
+collectPatBinders. In a lazy pattern, for example f ~(C x y) = ...,
+we want to generate bindings for x,y but not for dictionaries bound by
+C. (The type checker ensures they would not be used.)
+