From 6ce037393b555389b84bc0e7af53757ba6f4347d Mon Sep 17 00:00:00 2001
From: Adam Gundry <adam@well-typed.com>
Date: Fri, 6 Nov 2020 20:14:14 +0000
Subject: Revert "Experiment with using as-patterns in updaters"

This reverts commit 828b222d14345423861658369751eccfb2b845e6.
---
 compiler/GHC/Tc/TyCl/Utils.hs | 30 +-----------------------------
 1 file changed, 1 insertion(+), 29 deletions(-)

diff --git a/compiler/GHC/Tc/TyCl/Utils.hs b/compiler/GHC/Tc/TyCl/Utils.hs
index 6fc52aa681..b61767c3be 100644
--- a/compiler/GHC/Tc/TyCl/Utils.hs
+++ b/compiler/GHC/Tc/TyCl/Utils.hs
@@ -984,31 +984,6 @@ mkRecordSelectorAndUpdater all_cons idDetails fl x_vars =
         rec_field = mkHsRecField (mkFieldOcc fl) (mkVarPat field_var)
         field_var = mkInternalName (mkBuiltinUnique 1) (getOccName sel_name) loc
 
-    -- Make the updater binding:
-    --   upd z@(C2 {fld = x}) = (\ y -> z { fld = y }, x)
-    -- ...
-    upd_bind = mkBind upd_name alts
-      where
-        alts = map mk_match cons_w_field ++ deflt
-
-        mk_match con = ( [mkAsPat z_var (mkRecConPat con [rec_field])]
-                       , expr con
-                       )
-        rec_field = mkHsRecField (mkFieldOcc fl) (mkVarPat field_var)
-        field_var = mkInternalName (mkBuiltinUnique 1) (getOccName sel_name) loc
-        y_var = mkInternalName (mkBuiltinUnique 2) (mkVarOccFS lbl) loc
-        z_var = mkInternalName (mkBuiltinUnique 3) (mkVarOcc "z") loc
-        expr con = mkLHsTupleExpr
-                   [ mkHsLam [mkVarPat y_var] update_expr
-                   , mkHsVar field_var
-                   ]
-        update_expr = L loc (RecordUpd
-            { rupd_ext  = Generated
-            , rupd_expr = mkHsVar z_var
-            , rupd_flds = [mkHsRecField (L loc unambiguous_fld) (mkHsVar y_var)] })
-        unambiguous_fld = Unambiguous sel_name (L loc (mkVarUnqual (flLabel fl)))
-
-{-
     -- Make the updater binding:
     --   upd z = (\ y -> z { fld = y }, fld z)
     upd_bind = mkBind upd_name [([mkVarPat z_var], expr)]
@@ -1064,7 +1039,7 @@ mkRecordSelectorAndUpdater all_cons idDetails fl x_vars =
             -- in the TyCon, i.e. maps fldN to xN.
             x_var :: FieldLabelNoUpdater -> Name
             x_var fl' = lookupNameEnv_NF x_vars (flSelector fl')
--}
+
 
     -- These are just boring constructors for bits of syntax, using the SrcSpan
     -- of the field (which is why they are not top-level).
@@ -1077,9 +1052,6 @@ mkRecordSelectorAndUpdater all_cons idDetails fl x_vars =
     mkVarPat :: Name -> LPat GhcRn
     mkVarPat var = L loc (VarPat noExtField (L loc var))
 
-    mkAsPat :: Name -> LPat GhcRn -> LPat GhcRn
-    mkAsPat var pat = L loc (AsPat noExtField (L loc var) pat)
-
     mkRecConPat :: ConLike -> [LHsRecField GhcRn (XRec GhcRn (Pat GhcRn))] -> LPat GhcRn
     mkRecConPat con rflds = L loc (ConPat noExtField (L loc (getName con))
                                         (RecCon (HsRecFields rflds Nothing)))
-- 
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