[commit: ghc] master: Add 'Lift' instances for 'NonEmpty' and 'Void' (47875bd)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/47875bd4d79ca633b589e63e320aa5a5c631d096/ghc

>---------------------------------------------------------------

commit 47875bd4d79ca633b589e63e320aa5a5c631d096
Author: Alec Theriault <alec.theriault at gmail.com>
Date:   Fri Nov 30 09:18:10 2018 -0500

    Add 'Lift' instances for 'NonEmpty' and 'Void'
    
    Summary:
    Since 'NonEmpty' and 'Void' are now part of 'base', it makes
    sense that we put 'Lift' instances for them in 'template-haskell'.
    Not doing so is going to force users to define their own (possibly
    colliding) orphan instances downstream.
    
    Test Plan: ./validate
    
    Reviewers: goldfire, bgamari, RyanGlScott
    
    Reviewed By: RyanGlScott
    
    Subscribers: RyanGlScott, rwbarton, carter
    
    GHC Trac Issues: #15961
    
    Differential Revision: https://phabricator.haskell.org/D5391


>---------------------------------------------------------------

47875bd4d79ca633b589e63e320aa5a5c631d096
 libraries/template-haskell/Language/Haskell/TH/Syntax.hs | 16 ++++++++++++++++
 libraries/template-haskell/changelog.md                  |  2 ++
 testsuite/tests/quotes/TH_localname.stderr               |  2 +-
 testsuite/tests/th/TH_Lift.hs                            |  3 +++
 4 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
index b75a048..ef44a5c 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
@@ -34,6 +34,8 @@ import Control.Monad.IO.Class (MonadIO (..))
 import System.IO        ( hPutStrLn, stderr )
 import Data.Char        ( isAlpha, isAlphaNum, isUpper )
 import Data.Int
+import Data.List.NonEmpty ( NonEmpty(..) )
+import Data.Void        ( Void, absurd )
 import Data.Word
 import Data.Ratio
 import GHC.Generics     ( Generic )
@@ -701,6 +703,17 @@ liftString :: String -> Q Exp
 -- Used in TcExpr to short-circuit the lifting for strings
 liftString s = return (LitE (StringL s))
 
+-- | @since 2.15.0.0
+instance Lift a => Lift (NonEmpty a) where
+  lift (x :| xs) = do
+    x' <- lift x
+    xs' <- lift xs
+    return (InfixE (Just x') (ConE nonemptyName) (Just xs'))
+
+-- | @since 2.15.0.0
+instance Lift Void where
+  lift = pure . absurd
+
 instance Lift () where
   lift () = return (ConE (tupleDataName 0))
 
@@ -752,6 +765,9 @@ leftName, rightName :: Name
 leftName  = mkNameG DataName "base" "Data.Either" "Left"
 rightName = mkNameG DataName "base" "Data.Either" "Right"
 
+nonemptyName :: Name
+nonemptyName = mkNameG DataName "base" "GHC.Base" ":|"
+
 -----------------------------------------------------
 --
 --              Generic Lift implementations
diff --git a/libraries/template-haskell/changelog.md b/libraries/template-haskell/changelog.md
index de8b96f..5dca983 100644
--- a/libraries/template-haskell/changelog.md
+++ b/libraries/template-haskell/changelog.md
@@ -12,6 +12,8 @@
     `Maybe [TyVarBndrQ]` argument. Non-API-breaking versions of these
     functions can be found in `Language.Haskell.TH.Lib`.
 
+  * Add `Lift` instances for `NonEmpty` and `Void`
+
 ## 2.14.0.0 *TBA*
 
   * Introduce an `addForeignFilePath` function, as well as a corresponding
diff --git a/testsuite/tests/quotes/TH_localname.stderr b/testsuite/tests/quotes/TH_localname.stderr
index 41eb988..df38597 100644
--- a/testsuite/tests/quotes/TH_localname.stderr
+++ b/testsuite/tests/quotes/TH_localname.stderr
@@ -19,7 +19,7 @@ TH_localname.hs:3:11: error:
                  Language.Haskell.TH.Syntax.Lift (Maybe a)
           -- Defined in ‘Language.Haskell.TH.Syntax’
         ...plus 14 others
-        ...plus 10 instances involving out-of-scope types
+        ...plus 12 instances involving out-of-scope types
         (use -fprint-potential-instances to see them all)
     • In the expression: Language.Haskell.TH.Syntax.lift y
       In the expression:
diff --git a/testsuite/tests/th/TH_Lift.hs b/testsuite/tests/th/TH_Lift.hs
index eff0f1b..87bd47b 100644
--- a/testsuite/tests/th/TH_Lift.hs
+++ b/testsuite/tests/th/TH_Lift.hs
@@ -9,6 +9,7 @@ import Data.Ratio
 import Data.Word
 import Data.Int
 import Numeric.Natural
+import Data.List.NonEmpty
 
 a :: Integer
 a = $( (\x -> [| x |]) (5 :: Integer) )
@@ -76,4 +77,6 @@ n = $( (\x -> [| x |]) () )
 o :: (Bool, Char, Int)
 o = $( (\x -> [| x |]) (True, 'x', 4 :: Int) )
 
+p :: NonEmpty Char
+p = $( (\x -> [| x |])  ('a' :| "bcde") )