From 0b1be3d96496e6bf98acaf721e661ec1a8a3643c Mon Sep 17 00:00:00 2001
From: Mitchell Rosen <mitchellwrosen@gmail.com>
Date: Mon, 27 Nov 2023 21:50:58 -0500
Subject: [PATCH] tiny cleanup

---
 ki/src/Ki/Internal/Propagating.hs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/ki/src/Ki/Internal/Propagating.hs b/ki/src/Ki/Internal/Propagating.hs
index 8ef0889..1b9a113 100644
--- a/ki/src/Ki/Internal/Propagating.hs
+++ b/ki/src/Ki/Internal/Propagating.hs
@@ -23,16 +23,18 @@ instance Exception Propagating where
 pattern PropagatingFrom :: Tid -> SomeException
 pattern PropagatingFrom childId <- (fromException -> Just Propagating {childId})
 
+pattern PropagatingThe :: SomeException -> SomeException
+pattern PropagatingThe exception <- (fromException -> Just Propagating {exception})
+
 -- A unique identifier for a thread within a scope. (Internal type alias)
 type Tid =
   Int
 
 -- Peel an outer Propagating layer off of some exception, if there is one.
 peelOffPropagating :: SomeException -> SomeException
-peelOffPropagating e0 =
-  case fromException e0 of
-    Just (Propagating _ e1) -> e1
-    Nothing -> e0
+peelOffPropagating = \case
+  PropagatingThe exception -> exception
+  exception -> exception
 
 -- @propagate exception child parent@ propagates @exception@ from @child@ to @parent@.
 propagate :: SomeException -> Tid -> ThreadId -> IO ()