Fix pretty printing of MINIMAL signatures

Reviewers: austin, alanz, bgamari

Reviewed By: alanz, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2836

compiler/hsSyn/HsBinds.hs

@@ -972,7 +972,8 @@ ppr_sig (InlineSig var inl)
                                    <+> pprPrefixOcc (unLoc var))
 ppr_sig (SpecInstSig src ty)
   = pragSrcBrackets src "{-# SPECIALISE" (text "instance" <+> ppr ty)
-ppr_sig (MinimalSig _ bf)         = pragBrackets (pprMinimalSig bf)
+ppr_sig (MinimalSig src bf)
+  = pragSrcBrackets src "{-# MINIMAL" (pprMinimalSig bf)
 ppr_sig (PatSynSig names sig_ty)
   = text "pattern" <+> pprVarSig (map unLoc names) (ppr sig_ty)
 ppr_sig (SCCFunSig src fn mlabel)
@@ -1013,7 +1014,7 @@ instance Outputable TcSpecPrag where
 
 pprMinimalSig :: (OutputableBndr name)
               => LBooleanFormula (Located name) -> SDoc
-pprMinimalSig (L _ bf) = text "MINIMAL" <+> ppr (fmap unLoc bf)
+pprMinimalSig (L _ bf) = ppr (fmap unLoc bf)
 
 {-
 ************************************************************************

testsuite/tests/printer/Ppr023.hs

@@ -35,3 +35,7 @@ class Foo a where
     baz :: a -> a -> Bool
     quux :: a -> a -> Bool
     {-# MINIMAL bar, (foo, baq | foo, quux) #-}
+
+class Foo2 a where
+  f :: a
+  {-# MiNiMaL f #-}