Replace [PostTc id Type] with PostTc id [Type]

This gives a clearer indication as to what gets filled in
when. It was suggested by Richard on D1152.

Test Plan: ./validate

Reviewers: austin, goldfire, bgamari

Reviewed By: goldfire, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D1245

compiler/hsSyn/Convert.hs

@@ -712,7 +712,9 @@ cvtl e = wrapL (cvt e)
                               ; return $ RecordCon c' noPostTcExpr (HsRecFields flds' Nothing)}
     cvt (RecUpdE e flds) = do { e' <- cvtl e
                               ; flds' <- mapM cvtFld flds
-                              ; return $ RecordUpd e' (HsRecFields flds' Nothing) [] [] [] }
+                              ; return $ RecordUpd e'
+                                          (HsRecFields flds' Nothing)
+                                          PlaceHolder PlaceHolder PlaceHolder }
     cvt (StaticE e)      = fmap HsStatic $ cvtl e
 
 {- Note [Dropping constructors]

compiler/hsSyn/HsExpr.hs

@@ -293,11 +293,12 @@ data HsExpr id
                 (HsRecordBinds id)
 --              (HsMatchGroup Id)  -- Filled in by the type checker to be
 --                                 -- a match that does the job
-                [DataCon]          -- Filled in by the type checker to the
-                                   -- _non-empty_ list of DataCons that have
-                                   -- all the upd'd fields
-                [PostTc id Type]   -- Argument types of *input* record type
-                [PostTc id Type]   --              and  *output* record type
+                (PostTc id [DataCon])
+                -- Filled in by the type checker to the
+                -- _non-empty_ list of DataCons that have
+                -- all the upd'd fields
+                (PostTc id [Type])  -- Argument types of *input* record type
+                (PostTc id [Type])  --              and  *output* record type
   -- For a type family, the arg types are of the *instance* tycon,
   -- not the family tycon
 

compiler/hsSyn/PlaceHolder.hs

@@ -12,6 +12,7 @@ import NameSet
 import RdrName
 import Var
 import Coercion
+import DataCon (DataCon)
 
 import Data.Data hiding ( Fixity )
 import BasicTypes       (Fixity)
@@ -102,4 +103,6 @@ type DataId id =
 
   , Data (PostTc id Type)
   , Data (PostTc id Coercion)
+  , Data (PostTc id [Type])
+  , Data (PostTc id [DataCon])
   )

compiler/parser/RdrHsSyn.hs

@@ -1178,7 +1178,8 @@ mkRecConstrOrUpdate (L l (HsVar c)) _ (fs,dd)
   | isRdrDataCon c
   = return (RecordCon (L l c) noPostTcExpr (mk_rec_fields fs dd))
 mkRecConstrOrUpdate exp _ (fs,dd)
-  = return (RecordUpd exp (mk_rec_fields fs dd) [] [] [])
+  = return (RecordUpd exp (mk_rec_fields fs dd)
+                      PlaceHolder PlaceHolder PlaceHolder)
 
 mk_rec_fields :: [LHsRecField id arg] -> Bool -> HsRecFields id arg
 mk_rec_fields fs False = HsRecFields { rec_flds = fs, rec_dotdot = Nothing }

compiler/rename/RnExpr.hs

@@ -258,7 +258,7 @@ rnExpr (RecordCon con_id _ rbinds)
 rnExpr (RecordUpd expr rbinds _ _ _)
   = do  { (expr', fvExpr) <- rnLExpr expr
         ; (rbinds', fvRbinds) <- rnHsRecBinds HsRecFieldUpd rbinds
-        ; return (RecordUpd expr' rbinds' [] [] [],
+        ; return (RecordUpd expr' rbinds' PlaceHolder PlaceHolder PlaceHolder,
                   fvExpr `plusFV` fvRbinds) }
 
 rnExpr (ExprWithTySig expr pty PlaceHolder)