[project @ 1998-02-28 12:14:33 by sof]

Generate a little bit less code for record selectors.

diff --git a/ghc/compiler/prelude/StdIdInfo.lhs b/ghc/compiler/prelude/StdIdInfo.lhs
index 75d803b..968dc9d 100644 (file)
--- a/ghc/compiler/prelude/StdIdInfo.lhs
+++ b/ghc/compiler/prelude/StdIdInfo.lhs
@@ -39,6 +39,7 @@ import TyCon          ( isNewTyCon, tyConDataCons, isDataTyCon )
 import FieldLabel      ( FieldLabel )
 import PrelVals                ( pAT_ERROR_ID )
 import Maybes
+import Maybe            ( isJust )
 import Outputable
 import Util            ( assoc )
 \end{code}             
@@ -153,10 +154,17 @@ addStandardIdInfo sel_id
        tyvar_tys             = mkTyVarTys tyvars
        
        [data_id] = mkTemplateLocals [data_ty]
-       sel_rhs = mkTyLam tyvars $
-                 mkValLam [data_id] $
-                 Case (Var data_id) (AlgAlts (catMaybes (map mk_maybe_alt data_cons))
-                                             (BindDefault data_id error_expr))
+        alts      = map mk_maybe_alt data_cons
+       sel_rhs   = mkTyLam tyvars $
+                   mkValLam [data_id] $
+                   Case (Var data_id) 
+                        -- if any of the constructors don't have the label, ...
+                        (if any (not . isJust) alts then
+                          AlgAlts (catMaybes alts) 
+                                  (BindDefault data_id error_expr)
+                         else
+                          AlgAlts (catMaybes alts) NoDefault)
+
        mk_maybe_alt data_con 
          = case maybe_the_arg_id of
                Nothing         -> Nothing