[project @ 2005-10-17 11:11:15 by simonpj]

[ghc-hetmet.git] / ghc / compiler / basicTypes / MkId.lhs

diff --git a/ghc/compiler/basicTypes/MkId.lhs b/ghc/compiler/basicTypes/MkId.lhs
index 4ff6a0c..02d2559 100644 (file)
--- a/ghc/compiler/basicTypes/MkId.lhs
+++ b/ghc/compiler/basicTypes/MkId.lhs
@@ -537,14 +537,15 @@ mkRecordSelId tycon field_label
        (arg_prefix, arg_ids)
           | isVanillaDataCon data_con          -- Instantiate from commmon base
           = ([], mkTemplateLocalsNum arg_base (dataConInstOrigArgTys data_con res_tys))
-          | otherwise
+          | otherwise          -- The case pattern binds type variables, which are used
+                               -- in the types of the arguments of the pattern
           = (dc_tyvars ++ mkTemplateLocalsNum arg_base (mkPredTys dc_theta),
              mkTemplateLocalsNum arg_base' dc_arg_tys)
 
        (dc_tyvars, dc_theta, dc_arg_tys, _, _) = dataConSig data_con
        arg_base' = arg_base + length dc_theta
 
-       unpack_base = arg_base' + length dc_theta
+       unpack_base = arg_base' + length dc_arg_tys
        uniqs = map mkBuiltinUnique [unpack_base..]
 
        the_arg_id  = assoc "mkRecordSelId:mk_alt" (field_lbls `zip` arg_ids) field_label