Refactor renamer datastructures

This patch significantly refactors key renamer datastructures (primarily Avail
and GlobalRdrElt) in order to treat DuplicateRecordFields in a more robust way.
In particular it allows the extension to be used with pattern synonyms (fixes
where mangled record selector names could be printed instead of field labels
(e.g. with -Wpartial-fields or hole fits, see new tests).

The key idea is the introduction of a new type GreName for names that may
represent either normal entities or field labels.  This is then used in
GlobalRdrElt and AvailInfo, in place of the old way of representing fields
using FldParent (yuck) and an extra list in AvailTC.

Updates the haddock submodule.

1 files changed, 13 insertions, 8 deletions

diff --git a/compiler/GHC/Iface/Rename.hs b/compiler/GHC/Iface/Rename.hs
index 66a8b477f1..aba0c006ca 100644
--- a/compiler/GHC/Iface/Rename.hs
+++ b/compiler/GHC/Iface/Rename.hs
@@ -240,20 +240,25 @@ rnModule mod = do
     return (renameHoleModule unit_state hmap mod)
 
 rnAvailInfo :: Rename AvailInfo
-rnAvailInfo (Avail n) = Avail <$> rnIfaceGlobal n
-rnAvailInfo (AvailTC n ns fs) = do
+rnAvailInfo (Avail c) = Avail <$> rnGreName c
+rnAvailInfo (AvailTC n ns) = do
     -- Why don't we rnIfaceGlobal the availName itself?  It may not
     -- actually be exported by the module it putatively is from, in
     -- which case we won't be able to tell what the name actually
     -- is.  But for the availNames they MUST be exported, so they
     -- will rename fine.
-    ns' <- mapM rnIfaceGlobal ns
-    fs' <- mapM rnFieldLabel fs
-    case ns' ++ map flSelector fs' of
+    ns' <- mapM rnGreName ns
+    case ns' of
         [] -> panic "rnAvailInfoEmpty AvailInfo"
-        (rep:rest) -> ASSERT2( all ((== nameModule rep) . nameModule) rest, ppr rep $$ hcat (map ppr rest) ) do
-                         n' <- setNameModule (Just (nameModule rep)) n
-                         return (AvailTC n' ns' fs')
+        (rep:rest) -> ASSERT2( all ((== childModule rep) . childModule) rest, ppr rep $$ hcat (map ppr rest) ) do
+                         n' <- setNameModule (Just (childModule rep)) n
+                         return (AvailTC n' ns')
+  where
+    childModule = nameModule . greNameMangledName
+
+rnGreName :: Rename GreName
+rnGreName (NormalGreName n) = NormalGreName <$> rnIfaceGlobal n
+rnGreName (FieldGreName fl) = FieldGreName  <$> rnFieldLabel fl
 
 rnFieldLabel :: Rename FieldLabel
 rnFieldLabel (FieldLabel l b sel) = do