Disambiguate reified closed type family kinds in TH

Summary:
A continuation of #8953. This fixes an oversight in which the
left-hand sides of closed type families, when reified in Template Haskell,
would not be given kind annotations, even when they are necessary for
disambiguation purposes in the presence of `PolyKinds`.

Fixes #8953 and #12646.

Test Plan: ./validate

Reviewers: hvr, bgamari, austin, goldfire

Reviewed By: goldfire

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2795

GHC Trac Issues: #8953, #12646

1 files changed, 16 insertions, 0 deletions

diff --git a/testsuite/tests/th/T12646.hs b/testsuite/tests/th/T12646.hs
new file mode 100644
index 0000000000..197d59e67b
--- /dev/null
+++ b/testsuite/tests/th/T12646.hs
@@ -0,0 +1,16 @@
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE TemplateHaskell #-}
+{-# LANGUAGE TypeFamilies #-}
+module T12646 where
+
+import Language.Haskell.TH
+import System.IO
+
+type family F (a :: k) :: * where
+    F (a :: * -> *) = Int
+    F (a :: k)      = Char
+
+$(do info <- reify ''F
+     runIO $ putStrLn $ pprint info
+     runIO $ hFlush stdout
+     return [])