Remove some redundant definitions/constraints

Starting with GHC 7.10 and base-4.8, `Monad` implies `Applicative`,
which allows to simplify some definitions to exploit the superclass
relationship. This a first refactoring to that end.

3 files changed, 1 insertions, 4 deletions

diff --git a/libraries/ghci/GHCi/TH.hs b/libraries/ghci/GHCi/TH.hs
index f379dbc546..717192e39d 100644
--- a/libraries/ghci/GHCi/TH.hs
+++ b/libraries/ghci/GHCi/TH.hs
@@ -72,7 +72,6 @@ instance Monad GHCiQ where
     do (m', s')  <- runGHCiQ m s
        (a,  s'') <- runGHCiQ (f m') s'
        return (a, s'')
-  return    = pure
   fail err  = GHCiQ $ \s -> throwIO (GHCiQException s err)
 
 getState :: GHCiQ QState
diff --git a/libraries/template-haskell/Language/Haskell/TH/PprLib.hs b/libraries/template-haskell/Language/Haskell/TH/PprLib.hs
index 594d7dc54d..378888d77f 100644
--- a/libraries/template-haskell/Language/Haskell/TH/PprLib.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/PprLib.hs
@@ -155,7 +155,6 @@ instance Applicative PprM where
       (<*>) = ap
 
 instance Monad PprM where
-    return = pure
     m >>= k  = PprM $ \s -> let (x, s') = runPprM m s
                             in runPprM (k x) s'
 
diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
index becbbd6d7a..269bb70753 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
@@ -52,7 +52,7 @@ import Numeric.Natural
 --
 -----------------------------------------------------
 
-class (Applicative m, Monad m) => Quasi m where
+class Monad m => Quasi m where
   qNewName :: String -> m Name
         -- ^ Fresh names
 
@@ -170,7 +170,6 @@ runQ (Q m) = m
 instance Monad Q where
   Q m >>= k  = Q (m >>= \x -> unQ (k x))
   (>>) = (*>)
-  return     = pure
   fail s     = report True s >> Q (fail "Q monad failure")
 
 instance Functor Q where