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+{-# LANGUAGE MultiParamTypeClasses, FlexibleInstances, FlexibleContexts, TypeFamilies #-}
+module PushedInAsGivens where 
+
+
+type family F a
+
+
+
+bar y = let foo :: (F Int ~ [a]) => a -> Int 
+            foo x = length [x,y]  
+      in (y,foo y)
+
+
+-- This example demonstrates why we need to push in 
+-- an unsolved wanted as a given and not a given/solved.
+-- [Wanted] F Int ~ [beta]
+--- forall a. F Int ~ [a] => a ~ beta 
+-- We we push in the [Wanted] as given, it will interact and solve the implication
+-- constraint, and finally we quantify over F Int ~ [beta]. If we push it in as
+-- Given/Solved, it will be discarded when we meet the given (F Int ~ [a]) and 
+-- we will not be able to solve the implication constraint.
+
+
+