[commit: ghc] wip/orf-reboot: Comment (3a53745)

[git at git.haskell.org]

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

On branch  : wip/orf-reboot
Link       : http://ghc.haskell.org/trac/ghc/changeset/3a537459b874a88d6e3b294bed6e5c4197661437/ghc

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

commit 3a537459b874a88d6e3b294bed6e5c4197661437
Author: Adam Gundry <adam at well-typed.com>
Date:   Sun Oct 11 20:23:38 2015 +0100

    Comment


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

3a537459b874a88d6e3b294bed6e5c4197661437
 compiler/typecheck/TcExpr.hs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/compiler/typecheck/TcExpr.hs b/compiler/typecheck/TcExpr.hs
index 5491161..1bdb193 100644
--- a/compiler/typecheck/TcExpr.hs
+++ b/compiler/typecheck/TcExpr.hs
@@ -1468,7 +1468,9 @@ disambiguateRecordBinds record_expr rbnds res_ty
       where
         (orphans, rbnds') = partitionWith pickParent rbnds
 
-        -- AMG TODO explain why this is fiddly
+        -- Previously ambiguous fields must be marked as used now that
+        -- we know which one is meant, but unambiguous ones shouldn't
+        -- be recorded again (giving duplicate deprecation warnings).
         f (fld, gre, was_unambiguous)
             = do { unless was_unambiguous $ do
                      let L loc rdr = hsRecUpdFieldRdr (unLoc fld)