+breaker then compiling Game.hs goes into an infinite loop. This
+happened when we gave is_con_app a lower score than inline candidates:
+
+ Tree.repTree
+ = __inline_me (/\a. \w w1 w2 ->
+ case Tree.$wrepTree @ a w w1 w2 of
+ { (# ww1, ww2 #) -> Branch @ a ww1 ww2 })
+ Tree.$wrepTree
+ = /\a w w1 w2 ->
+ (# w2_smP, map a (Tree a) (Tree.repTree a w1 w) (w w2) #)
+
+Here we do *not* want to choose 'repTree' as the loop breaker.
+
+Note [DFuns should not be loop breakers]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+It's particularly bad to make a DFun into a loop breaker. See
+Note [How instance declarations are translated] in TcInstDcls
+
+We give DFuns a higher score than ordinary CONLIKE things because
+if there's a choice we want the DFun to be the non-looop breker. Eg
+
+rec { sc = /\ a \$dC. $fBWrap (T a) ($fCT @ a $dC)
+
+ $fCT :: forall a_afE. (Roman.C a_afE) => Roman.C (Roman.T a_afE)
+ {-# DFUN #-}
+ $fCT = /\a \$dC. MkD (T a) ((sc @ a $dC) |> blah) ($ctoF @ a $dC)
+ }
+
+Here 'sc' (the superclass) looks CONLIKE, but we'll never get to it
+if we can't unravel the DFun first.