Refactor renamer datastructureswip/amg/renamer-refactor

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, 5 insertions, 7 deletions

diff --git a/compiler/GHC/Rename/Module.hs b/compiler/GHC/Rename/Module.hs
index d47d652358..e098156d1d 100644
--- a/compiler/GHC/Rename/Module.hs
+++ b/compiler/GHC/Rename/Module.hs
@@ -1613,7 +1613,6 @@ getParent rdr_env n
   = case lookupGRE_Name rdr_env n of
       Just gre -> case gre_par gre of
                     ParentIs  { par_is = p } -> p
-                    FldParent { par_is = p } -> p
                     _                        -> n
       Nothing -> n
 
@@ -2389,7 +2388,8 @@ extendPatSynEnv val_decls local_fix_env thing = do {
      names_with_fls <- new_ps val_decls
    ; let pat_syn_bndrs = concat [ name: map flSelector fields
                                 | (name, fields) <- names_with_fls ]
-   ; let avails = map avail pat_syn_bndrs
+   ; let avails = map avail (map fst names_with_fls)
+               ++ map availField (concatMap snd names_with_fls)
    ; (gbl_env, lcl_env) <- extendGlobalRdrEnvRn avails local_fix_env
 
    ; let field_env' = extendNameEnvList (tcg_field_env gbl_env) names_with_fls
@@ -2408,11 +2408,9 @@ extendPatSynEnv val_decls local_fix_env thing = do {
                                        , psb_args = RecCon as }))) <- bind
       = do
           bnd_name <- newTopSrcBinder (L bind_loc n)
-          let rnames = map recordPatSynSelectorId as
-              mkFieldOcc :: Located RdrName -> LFieldOcc GhcPs
-              mkFieldOcc (L l name) = L l (FieldOcc noExtField (L l name))
-              field_occs =  map mkFieldOcc rnames
-          flds     <- mapM (newRecordSelector False [bnd_name]) field_occs
+          let field_occs = map ((\ f -> L (getLoc (rdrNameFieldOcc f)) f) . recordPatSynField) as
+          overload_ok <- xoptM LangExt.DuplicateRecordFields
+          flds <- mapM (newRecordSelector overload_ok [bnd_name]) field_occs
           return ((bnd_name, flds): names)
       | L bind_loc (PatSynBind _ (PSB { psb_id = L _ n})) <- bind
       = do