From b92fb5150bdc6a0a090ecba2927c14e19005116e Mon Sep 17 00:00:00 2001
From: Ryan Scott <ryan.gl.scott@gmail.com>
Date: Mon, 15 Jan 2018 13:51:55 -0500
Subject: Parenthesize forall-type args in cvtTypeKind

Trac #14646 happened because we forgot to parenthesize `forall` types to
the left of an arrow. This simple patch fixes that.

Test Plan: make test TEST=T14646

Reviewers: alanz, goldfire, bgamari

Reviewed By: alanz

Subscribers: rwbarton, thomie, carter

GHC Trac Issues: #14646

Differential Revision: https://phabricator.haskell.org/D4298

(cherry picked from commit f380115cd834ffbe51aca60f5476a51b94cdd413)
---
 compiler/hsSyn/Convert.hs        | 9 +++++----
 testsuite/tests/th/T14646.hs     | 6 ++++++
 testsuite/tests/th/T14646.stderr | 6 ++++++
 testsuite/tests/th/all.T         | 1 +
 4 files changed, 18 insertions(+), 4 deletions(-)
 create mode 100644 testsuite/tests/th/T14646.hs
 create mode 100644 testsuite/tests/th/T14646.stderr

diff --git a/compiler/hsSyn/Convert.hs b/compiler/hsSyn/Convert.hs
index b032538a66..aea37c9bc6 100644
--- a/compiler/hsSyn/Convert.hs
+++ b/compiler/hsSyn/Convert.hs
@@ -1221,10 +1221,11 @@ cvtTypeKind ty_str ty
                         tys'
            ArrowT
              | [x',y'] <- tys' -> do
-                 case x' of
-                   (L _ HsFunTy{}) -> do { x'' <- returnL (HsParTy x')
-                                         ; returnL (HsFunTy x'' y') }
-                   _  -> returnL (HsFunTy x' y')
+                 x'' <- case x' of
+                          L _ HsFunTy{}    -> returnL (HsParTy x')
+                          L _ HsForAllTy{} -> returnL (HsParTy x') -- #14646
+                          _                -> return x'
+                 returnL (HsFunTy x'' y')
              | otherwise ->
                   mk_apps (HsTyVar NotPromoted (noLoc (getRdrName funTyCon)))
                           tys'
diff --git a/testsuite/tests/th/T14646.hs b/testsuite/tests/th/T14646.hs
new file mode 100644
index 0000000000..c85872365f
--- /dev/null
+++ b/testsuite/tests/th/T14646.hs
@@ -0,0 +1,6 @@
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE TemplateHaskell #-}
+module T14646 where
+
+$([d| f :: (forall a. a) -> Int
+      f _ = undefined |])
diff --git a/testsuite/tests/th/T14646.stderr b/testsuite/tests/th/T14646.stderr
new file mode 100644
index 0000000000..869cf6fd01
--- /dev/null
+++ b/testsuite/tests/th/T14646.stderr
@@ -0,0 +1,6 @@
+T14646.hs:(5,3)-(6,24): Splicing declarations
+    [d| f :: (forall a. a) -> Int
+        f _ = undefined |]
+  ======>
+    f :: (forall a. a) -> Int
+    f _ = undefined
diff --git a/testsuite/tests/th/all.T b/testsuite/tests/th/all.T
index 0ad178e691..1fae4c6af8 100644
--- a/testsuite/tests/th/all.T
+++ b/testsuite/tests/th/all.T
@@ -397,3 +397,4 @@ test('T13887', normal, compile_and_run, ['-v0'])
 test('T13968', normal, compile_fail, ['-v0'])
 test('T14204', normal, compile_fail, ['-v0'])
 test('T14060', normal, compile_and_run, ['-v0'])
+test('T14646', normal, compile, ['-v0 -ddump-splices -dsuppress-uniques'])
-- 
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