Fi test

Author: saulshanabrook

mypy/checkpattern.py

@@ -247,8 +247,9 @@ def visit_sequence_pattern(self, o: SequencePattern) -> PatternType:
         # get inner types of original type
         #
         # 1. Go through all possible types and filter to only those which are sequences that could match that number of items
-        # 2. If there are multiple tuples left with unpacks, then use the fallback logic where we union all items types
-        # 3. Otherwise, take the product of the item types so that each index can have a unique type
+        # 2. If there is exactly one tuple left with an unpack, then use that type and the unpack index
+        # 3. Otherwise, take the product of the item types so that each index can have a unique type. For tuples with unpack
+        #    fallback to merging all of their types for each index since we can't handle multiple unpacked items at once yet.
 
         #  state of matching
         state: (
@@ -303,7 +304,6 @@ def visit_sequence_pattern(self, o: SequencePattern) -> PatternType:
                 state = ("MULTI_UNPACK", [[self.chk.iterable_item_type(tuple_fallback(state[1]), o)] * n_patterns])
             assert state[0] != "UNPACK" # for type checker
             state[1].append(inner_t)
-
         if state[0] == "UNPACK":
             _, update_tuple_type, unpack_index, union_index = state
             inner_types = update_tuple_type.items

test-data/unit/check-python310.test

@@ -1602,11 +1602,11 @@ match m6:
         reveal_type(b6)  # N: Revealed type is "Union[builtins.int, builtins.float, builtins.str]"
 
 # but do still seperate types from non unpacked types
-m7: tuple[int, Unpack[tuple[float, ...]]] | tuple[str, bool]
+m7: tuple[int, Unpack[tuple[float, ...]]] | tuple[str, str]
 match m7:
     case (a7, b7, *rest7):
         reveal_type(a7)  # N: Revealed type is "Union[builtins.int, builtins.float, builtins.str]"
-        reveal_type(b7)  # N: Revealed type is "Union[builtins.int, builtins.float, builtins.bool]"
+        reveal_type(b7)  # N: Revealed type is "Union[builtins.int, builtins.float, builtins.str]"
         reveal_type(rest7)  # N: Revealed type is "builtins.list[Union[builtins.int, builtins.float]]"
 
 # verify that if we are unpacking, it will get the type of the sequence if the tuple is too short