From e40db7b1676627f5291b463405338e7b69fa3f69 Mon Sep 17 00:00:00 2001
From: Simon Peyton Jones <simonpj@microsoft.com>
Date: Wed, 13 Dec 2017 10:46:26 +0000
Subject: Detect levity-polymorphic uses of unsafeCoerce#

This bug was shown up by Trac #14561. The deguarer carefully
detects unsaturated and levity-polymorphic uses of primops,
but not of things like unsafeCoerce#.

The fix is simple: see Note [Levity-polymorphic Ids] in Id.
---
 testsuite/tests/polykinds/T14561.hs | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
 create mode 100644 testsuite/tests/polykinds/T14561.hs

(limited to 'testsuite/tests/polykinds/T14561.hs')

diff --git a/testsuite/tests/polykinds/T14561.hs b/testsuite/tests/polykinds/T14561.hs
new file mode 100644
index 0000000000..f528e7c813
--- /dev/null
+++ b/testsuite/tests/polykinds/T14561.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE TypeInType #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE MagicHash #-}
+
+module T14561 where
+
+import GHC.Types
+import GHC.Prim
+
+badId :: forall (a :: TYPE r). a -> a
+badId = unsafeCoerce#
+-- Un-saturated application of a levity-polymorphic
+-- function that must be eta-expanded
+
+goodId :: forall (a :: Type). a -> a
+goodId = unsafeCoerce#
+-- But this one is OK
-- 
cgit v1.2.1