X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;ds=sidebyside;f=compiler%2FdeSugar%2FMatch.lhs;h=d793343e4177b8ec2180e7420265ab8d05fcc8c6;hb=3cec5683766a13019c2835a4e79cc7e7dc066b96;hp=2d646339afbfd0ab20cf7e40a2bb9232ad4d26a0;hpb=133d09024cdead191873088b7248f5d96aafe60f;p=ghc-hetmet.git

diff --git a/compiler/deSugar/Match.lhs b/compiler/deSugar/Match.lhs
index 2d64633..d793343 100644
--- a/compiler/deSugar/Match.lhs
+++ b/compiler/deSugar/Match.lhs
@@ -745,6 +745,10 @@ sameGroup (PgN l1)   (PgN l2)   = True		-- Needs conditionals
 sameGroup (PgNpK l1) (PgNpK l2) = l1==l2	-- Order is significant
 						-- See Note [Order of n+k]
 sameGroup (PgCo	t1)  (PgCo t2)  = t1 `coreEqType` t2
+	-- CoPats are in the same goup only if the type of the
+	-- enclosed pattern is the same. The patterns outside the CoPat
+	-- always have the same type, so this boils down to saying that
+	-- the two coercions are identical.
 sameGroup _          _          = False
  
 patGroup :: Pat Id -> PatGroup