-- It's only a one-way match; unlike instance matching we
-- don't consider unification
--
--- Notice that there is no case
--- ruleCantMatch (Just n1 : ts) (Nothing : as) = True
--- Reason: a local variable 'v' in the actuals might
--- have an unfolding which is a global.
--- This quite often happens with case scrutinees.
+-- Notice that [_$_]
+-- ruleCantMatch [Nothing] [Just n2] = False
+-- Reason: a template variable can be instantiated by a constant
+-- Also:
+-- ruleCantMatch [Just n1] [Nothing] = False
+-- Reason: a local variable 'v' in the actuals might [_$_]
+
ruleCantMatch (Just n1 : ts) (Just n2 : as) = n1 /= n2 || ruleCantMatch ts as
ruleCantMatch (t : ts) (a : as) = ruleCantMatch ts as
ruleCantMatch ts as = False
findBest target (rule1,ans1) ((rule2,ans2):prs)
| rule1 `isMoreSpecific` rule2 = findBest target (rule1,ans1) prs
| rule2 `isMoreSpecific` rule1 = findBest target (rule2,ans2) prs
-#ifdef DEBUG
- | otherwise = let pp_rule rule
+ | debugIsOn = let pp_rule rule
| opt_PprStyle_Debug = ppr rule
| otherwise = doubleQuotes (ftext (ru_name rule))
in pprTrace "Rules.findBest: rule overlap (Rule 1 wins)"
ptext SLIT("Rule 1:") <+> pp_rule rule1,
ptext SLIT("Rule 2:") <+> pp_rule rule2]) $
findBest target (rule1,ans1) prs
-#else
| otherwise = findBest target (rule1,ans1) prs
-#endif
where
(fn,args) = target