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authorRyan Scott <ryan.gl.scott@gmail.com>2020-08-01 13:33:33 -0400
committerMarge Bot <ben+marge-bot@smart-cactus.org>2020-08-05 04:01:51 -0400
commitfbcb886d503dd7aaebc4c40e59615068b3fd0bd7 (patch)
treeefc61eca378f0d2b3a33d14efc482a5c1b2f63c2 /libraries
parenteb7013c3037538aa9c947a21dbbfd7c297929ac8 (diff)
downloadhaskell-fbcb886d503dd7aaebc4c40e59615068b3fd0bd7.tar.gz
Make CodeQ and TExpQ levity polymorphic
The patch is quite straightforward. The only tricky part is that `Language.Haskell.TH.Lib.Internal` now must be `Trustworthy` instead of `Safe` due to the `GHC.Exts` import (in order to import `TYPE`). Since `CodeQ` has yet to appear in any released version of `template-haskell`, I didn't bother mentioning the change to `CodeQ` in the `template-haskell` release notes. Fixes #18521.
Diffstat (limited to 'libraries')
-rw-r--r--libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs19
-rw-r--r--libraries/template-haskell/Language/Haskell/TH/Syntax.hs2
-rw-r--r--libraries/template-haskell/changelog.md2
3 files changed, 20 insertions, 3 deletions
diff --git a/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs b/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs
index cb19882a97..fa38e6a933 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Lib/Internal.hs
@@ -1,4 +1,5 @@
-{-# LANGUAGE Safe #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE Trustworthy #-}
-- |
-- Language.Haskell.TH.Lib.Internal exposes some additional functionality that
@@ -19,19 +20,31 @@ module Language.Haskell.TH.Lib.Internal where
import Language.Haskell.TH.Syntax hiding (Role, InjectivityAnn)
import qualified Language.Haskell.TH.Syntax as TH
import Control.Applicative(liftA, liftA2)
+import qualified Data.Kind as Kind (Type)
import Data.Word( Word8 )
+import GHC.Exts (TYPE)
import Prelude
----------------------------------------------------------
-- * Type synonyms
----------------------------------------------------------
+-- Since GHC 8.8 is currently the minimum boot compiler version that we must
+-- support, we must use inline kind signatures to make TExpQ and CodeQ
+-- levity polymorphic. When we drop support for GHC 8.8, we can instead use
+-- standalone kind signatures, which are provided as comments.
+
+-- | Levity-polymorphic since /template-haskell-2.17.0.0/.
+-- type TExpQ :: TYPE r -> Kind.Type
+type TExpQ (a :: TYPE r) = Q (TExp a)
+
+-- type CodeQ :: TYPE r -> Kind.Type
+type CodeQ = Code Q :: (TYPE r -> Kind.Type)
+
type InfoQ = Q Info
type PatQ = Q Pat
type FieldPatQ = Q FieldPat
type ExpQ = Q Exp
-type TExpQ a = Q (TExp a)
-type CodeQ = Code Q
type DecQ = Q Dec
type DecsQ = Q [Dec]
type Decs = [Dec] -- Defined as it is more convenient to wire-in
diff --git a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
index dac97c641f..9c47b6cfdd 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Syntax.hs
@@ -341,6 +341,8 @@ newtype TExp (a :: TYPE (r :: RuntimeRep)) = TExp
-- • In the Template Haskell quotation [|| "foo" ||]
-- In the expression: [|| "foo" ||]
-- In the Template Haskell splice $$([|| "foo" ||])
+--
+-- Levity-polymorphic since /template-haskell-2.16.0.0/.
-- | Discard the type annotation and produce a plain Template Haskell
-- expression
diff --git a/libraries/template-haskell/changelog.md b/libraries/template-haskell/changelog.md
index eb72b11858..8cd88b5ccc 100644
--- a/libraries/template-haskell/changelog.md
+++ b/libraries/template-haskell/changelog.md
@@ -32,6 +32,8 @@
* Add support for QualifiedDo. The data constructors `DoE` and `MDoE` got a new
`Maybe ModName` argument to describe the qualifier of do blocks.
+ * The argument to `TExpQ` can now be levity polymorphic.
+
## 2.16.0.0 *TBA*
* Add support for tuple sections. (#15843) The type signatures of `TupE` and