Support stage 1 Template Haskell (non-quasi) quotes, fixes #10382.

Summary:
This commit adds stage 1 support for Template Haskell
quoting, e.g. [| ... expr ... |], which is useful
for authors of quasiquoter libraries that do not actually
need splices.  The TemplateHaskell extension now does not
unconditionally fail; it only fails if the renamer encounters
a splice that it can't run.

In order to make sure the referenced data structures
are consistent, template-haskell is now a boot library.
There are some minor BC changes to template-haskell to make it boot
on GHC 7.8.

Note for reviewer: big diff changes are simply code
being moved out of an ifdef; there was no other substantive
change to that code.

Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>

Test Plan: validate

Reviewers: simonpj, austin, goldfire

Subscribers: bgamari, thomie

Differential Revision: https://phabricator.haskell.org/D876

GHC Trac Issues: #10382

3 files changed, 22 insertions, 5 deletions

diff --git a/libraries/template-haskell/Language/Haskell/TH/PprLib.hs b/libraries/template-haskell/Language/Haskell/TH/PprLib.hs
index a6b923cc35..68134965a5 100644
--- a/libraries/template-haskell/Language/Haskell/TH/PprLib.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/PprLib.hs
@@ -1,4 +1,4 @@
-{-# LANGUAGE FlexibleInstances #-}
+{-# LANGUAGE CPP, FlexibleInstances #-}
 
 -- | Monadic front-end to Text.PrettyPrint
 
@@ -41,6 +41,9 @@ import qualified Text.PrettyPrint as HPJ
 import Control.Monad (liftM, liftM2, ap)
 import Language.Haskell.TH.Lib.Map ( Map )
 import qualified Language.Haskell.TH.Lib.Map as Map ( lookup, insert, empty )
+#if __GLASGOW_HASKELL__ < 709
+import Control.Applicative( Applicative(..) )
+#endif
 
 infixl 6 <> 
 infixl 6 <+>
diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
index 29be27a9a2..8879c62d19 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
@@ -1,6 +1,10 @@
 {-# LANGUAGE CPP, DeriveDataTypeable, PolymorphicComponents,
              RoleAnnotations, DeriveGeneric, FlexibleInstances #-}
 
+#if MIN_VERSION_base(4,8,0)
+#define HAS_NATURAL
+#endif
+
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Language.Haskell.Syntax
@@ -29,16 +33,19 @@ import Data.Char        ( isAlpha, isAlphaNum, isUpper )
 import Data.Int
 import Data.Word
 import Data.Ratio
-import Numeric.Natural
 import GHC.Generics     ( Generic )
 
+#ifdef HAS_NATURAL
+import Numeric.Natural
+#endif
+
 -----------------------------------------------------
 --
 --              The Quasi class
 --
 -----------------------------------------------------
 
-class Monad m => Quasi m where
+class (Applicative m, Monad m) => Quasi m where
   qNewName :: String -> m Name
         -- ^ Fresh names
 
@@ -487,8 +494,10 @@ instance Lift Word32 where
 instance Lift Word64 where
   lift x = return (LitE (IntegerL (fromIntegral x)))
 
+#ifdef HAS_NATURAL
 instance Lift Natural where
   lift x = return (LitE (IntegerL (fromIntegral x)))
+#endif
 
 instance Integral a => Lift (Ratio a) where
   lift x = return (LitE (RationalL (toRational x)))
diff --git a/libraries/template-haskell/template-haskell.cabal b/libraries/template-haskell/template-haskell.cabal
index 1c53af392e..bd277d127c 100644
--- a/libraries/template-haskell/template-haskell.cabal
+++ b/libraries/template-haskell/template-haskell.cabal
@@ -48,9 +48,14 @@ Library
         Language.Haskell.TH.Lib.Map
 
     build-depends:
-        base       == 4.8.*,
+        base       >= 4.7 && < 4.9,
         pretty     == 1.1.*
 
     -- We need to set the package key to template-haskell (without a
     -- version number) as it's magic.
-    ghc-options: -Wall -this-package-key template-haskell
+    ghc-options: -Wall
+
+    if impl( ghc >= 7.9 )
+        ghc-options:  -this-package-key template-haskell
+    else
+        ghc-options:  -package-name template-haskell