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, 4 insertions, 3 deletions

diff --git a/compiler/GHC/Tc/Utils/Backpack.hs b/compiler/GHC/Tc/Utils/Backpack.hs
index 7fff1a9e35..c1888c7f36 100644
--- a/compiler/GHC/Tc/Utils/Backpack.hs
+++ b/compiler/GHC/Tc/Utils/Backpack.hs
@@ -174,7 +174,8 @@ checkHsigIface tcg_env gr sig_iface
       -- The hsig did NOT define this function; that means it must
       -- be a reexport.  In this case, make sure the 'Name' of the
       -- reexport matches the 'Name exported here.
-      | [GRE { gre_name = name' }] <- lookupGlobalRdrEnv gr (nameOccName name) =
+      | [gre] <- lookupGlobalRdrEnv gr (nameOccName name) = do
+        let name' = greMangledName gre
         when (name /= name') $ do
             -- See Note [Error reporting bad reexport]
             -- TODO: Actually this error swizzle doesn't work
@@ -751,7 +752,7 @@ mergeSignatures
     let ifaces = lcl_iface : ext_ifaces
 
     -- STEP 4.1: Merge fixities (we'll verify shortly) tcg_fix_env
-    let fix_env = mkNameEnv [ (gre_name rdr_elt, FixItem occ f)
+    let fix_env = mkNameEnv [ (greMangledName rdr_elt, FixItem occ f)
                             | (occ, f) <- concatMap mi_fixities ifaces
                             , rdr_elt <- lookupGlobalRdrEnv rdr_env occ ]
 
@@ -951,7 +952,7 @@ checkImplements impl_mod req_mod@(Module uid mod_name) = do
 
     let avails = calculateAvails home_unit
                     impl_iface False{- safe -} NotBoot ImportedBySystem
-        fix_env = mkNameEnv [ (gre_name rdr_elt, FixItem occ f)
+        fix_env = mkNameEnv [ (greMangledName rdr_elt, FixItem occ f)
                             | (occ, f) <- mi_fixities impl_iface
                             , rdr_elt <- lookupGlobalRdrEnv impl_gr occ ]
     updGblEnv (\tcg_env -> tcg_env {