[commit: ghc] master: Comments only (e9d3e28)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/e9d3e28afc8b473e250ae43eabd928809c4a4c3a/ghc

>---------------------------------------------------------------

commit e9d3e28afc8b473e250ae43eabd928809c4a4c3a
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Tue Nov 11 11:36:16 2014 +0000

    Comments only


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e9d3e28afc8b473e250ae43eabd928809c4a4c3a
 compiler/typecheck/TcFlatten.lhs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler/typecheck/TcFlatten.lhs b/compiler/typecheck/TcFlatten.lhs
index 3ee4d59..2e9c6eb 100644
--- a/compiler/typecheck/TcFlatten.lhs
+++ b/compiler/typecheck/TcFlatten.lhs
@@ -601,6 +601,9 @@ goals.  But to be honest I'm not absolutely certain, so I am leaving
 FM_Avoid in the code base.  What I'm removing is the unique place
 where it is *used*, namely in TcCanonical.canEqTyVar.
 
+See also Note [Conservative unification check] in TcUnify, which gives
+other examples where lazy flattening caused problems.
+
 Bottom line: FM_Avoid is unused for now (Nov 14).
 Note: T5321Fun got faster when I disabled FM_Avoid
       T5837 did too, but it's pathalogical anyway