Merge pull request #3970 from ezyang/pr/fix-werror-tracetree

Fix -Werror failure.

cabal-install/Distribution/Solver/Modular/Solver.hs

@@ -14,7 +14,6 @@ import Data.Set as S
 import Distribution.Version
 
 import Distribution.Compiler (CompilerInfo)
-import Distribution.Text (display)
 
 import Distribution.Solver.Types.PackagePath
 import Distribution.Solver.Types.PackagePreferences
@@ -45,6 +44,7 @@ import Distribution.Simple.Setup (BooleanFlag(..))
 import Distribution.Solver.Modular.Flag
 import qualified Distribution.Solver.Modular.ConflictSet as CS
 import qualified Distribution.Solver.Modular.WeightedPSQ as W
+import qualified Distribution.Text as T
 
 import Debug.Trace.Tree (gtraceJson)
 import Debug.Trace.Tree.Simple
@@ -202,7 +202,7 @@ instance GSimpleTree (Tree d QGoalReason) where
 
       -- Show package choice
       goP :: QPN -> POption -> Tree d QGoalReason -> (String, SimpleTree)
-      goP _        (POption (I ver _loc) Nothing)  subtree = (display ver, go subtree)
+      goP _        (POption (I ver _loc) Nothing)  subtree = (T.display ver, go subtree)
       goP (Q _ pn) (POption _           (Just pp)) subtree = (showQPN (Q pp pn), go subtree)
 
       -- Show flag or stanza choice