-prepareRules dflags pkg_rule_base hst us binds local_rules
- = do { let (better_rules,_) = initSmpl dflags sw_chkr us local_ids black_list_all
- (mapSmpl simplRule local_rules)
+prepareRules dflags pkg_rule_base hpt us binds local_rules
+ = do { let env = emptySimplEnv SimplGently [] local_ids
+ (better_rules,_) = initSmpl dflags us (mapSmpl (simplRule env) local_rules)
+
+ ; let (local_rules, orphan_rules) = partition ((`elemVarSet` local_ids) . fst) better_rules
+ -- We use (`elemVarSet` local_ids) rather than isLocalId because
+ -- isLocalId isn't true of class methods.
+ -- If we miss any rules for Ids defined here, then we end up
+ -- giving the local decl a new Unique (because the in-scope-set is the
+ -- same as the rule-id set), and now the binding for the class method
+ -- doesn't have the same Unique as the one in the Class and the tc-env
+ -- Example: class Foo a where
+ -- op :: a -> a
+ -- {-# RULES "op" op x = x #-}