Update for_helpers.py

Author: BobTheBuidler

mypyc/irbuild/for_helpers.py

@@ -1209,22 +1209,33 @@ def check_type(obj: Any, typ: Type[Any]) -> bool:
 
         # forward involves in the best case one pyssize_t comparison, else one length check + the comparison
         # reverse is slightly slower than forward, with one extra check
-        for_sequence_reverse = [
+        for_sequence_reverse_with_len_check = [
             g
             for g in gens
-            if check_type(g, ForSequence) and (g.gen if isinstance(g, ForEnumerate) else g).reverse
+            if check_type(g, ForSequence) and (g := (g.gen if isinstance(g, ForEnumerate) else g)).reverse and g.len_reg is not None
         ]
-        for_sequence_forward = [
+        for_sequence_reverse_no_len_check = [
+            g
+            for g in gens
+            if check_type(g, ForSequence) and (g := (g.gen if isinstance(g, ForEnumerate) else g)).reverse and g.len_reg is None
+        ]
+        for_sequence_forward_with_len_check = [
+            g
+            for g in gens
+            if check_type(g, ForSequence)
+            and not (g := (g.gen if isinstance(g, ForEnumerate) else g)).reverse and g.len_reg is not None
+        ]
+        for_sequence_forward_no_len_check = [
             g
             for g in gens
             if check_type(g, ForSequence)
-            and not (g.gen if isinstance(g, ForEnumerate) else g).reverse
+            and not (g := (g.gen if isinstance(g, ForEnumerate) else g)).reverse and g.len_reg is None
         ]
 
         # these are really fast, just a C int equality check
         for_range = [g for g in gens if isinstance(g, ForRange)]
 
-        ordered = for_range + for_sequence_forward + for_sequence_reverse + for_native + for_dict
+        ordered = for_range + for_sequence_forward_no_len_check + for_sequence_forward_no_len_check + for_sequence_forward_with_len_check + for_sequence_reverse_with_len_check + for_native + for_dict
 
         # this is a failsafe for ForHelper classes which might have been added after this commit but not added to this function's code
         leftovers = [g for g in gens if g not in ordered + for_iterable]