Imply 3.8+ when annotated assigments used with unparenthesized tuples

CHANGES.md

@@ -12,6 +12,8 @@
 - No longer color diff headers white as it's unreadable in light themed terminals
   (#2691)
 - Tuple unpacking on `return` and `yield` constructs now implies 3.8+ (#2700)
+- Unparenthesized tuples on annotated assignments (e.g
+  `values: Tuple[int, ...] = 1, 2, 3`) now implies 3.8+ (#2708)
 
 ## 21.12b0
 

src/black/__init__.py

@@ -1218,6 +1218,13 @@ def get_features_used(  # noqa: C901
         ):
             features.add(Feature.UNPACKING_ON_FLOW)
 
+        elif (
+            n.type == syms.annassign
+            and len(n.children) >= 4
+            and n.children[3].type == syms.testlist_star_expr
+        ):
+            features.add(Feature.ANN_ASSIGN_EXTENDED_RHS)
+
         # Python 2 only features (for its deprecation) except for integers, see above
         elif n.type == syms.print_stmt:
             features.add(Feature.PRINT_STMT)

src/black/mode.py

@@ -50,6 +50,7 @@ class Feature(Enum):
     RELAXED_DECORATORS = 10
     PATTERN_MATCHING = 11
     UNPACKING_ON_FLOW = 12
+    ANN_ASSIGN_EXTENDED_RHS = 13
     FORCE_OPTIONAL_PARENTHESES = 50
 
     # __future__ flags
@@ -118,6 +119,7 @@ class Feature(Enum):
         Feature.ASSIGNMENT_EXPRESSIONS,
         Feature.POS_ONLY_ARGUMENTS,
         Feature.UNPACKING_ON_FLOW,
+        Feature.ANN_ASSIGN_EXTENDED_RHS,
     },
     TargetVersion.PY39: {
         Feature.UNICODE_LITERALS,
@@ -131,6 +133,7 @@ class Feature(Enum):
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,
         Feature.UNPACKING_ON_FLOW,
+        Feature.ANN_ASSIGN_EXTENDED_RHS,
     },
     TargetVersion.PY310: {
         Feature.UNICODE_LITERALS,
@@ -144,6 +147,7 @@ class Feature(Enum):
         Feature.RELAXED_DECORATORS,
         Feature.POS_ONLY_ARGUMENTS,
         Feature.UNPACKING_ON_FLOW,
+        Feature.ANN_ASSIGN_EXTENDED_RHS,
         Feature.PATTERN_MATCHING,
     },
 }

tests/test_black.py

@@ -818,6 +818,18 @@ def test_get_features_used(self) -> None:
         self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
         node = black.lib2to3_parse("def fn(): return a, *b, c")
         self.assertEqual(black.get_features_used(node), {Feature.UNPACKING_ON_FLOW})
+        node = black.lib2to3_parse("x = a, *b, c")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = regular")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = (regular, regular)")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Any = Complex(Type(1))[something]")
+        self.assertEqual(black.get_features_used(node), set())
+        node = black.lib2to3_parse("x: Tuple[int, ...] = a, b, c")
+        self.assertEqual(
+            black.get_features_used(node), {Feature.ANN_ASSIGN_EXTENDED_RHS}
+        )
 
     def test_get_features_used_for_future_flags(self) -> None:
         for src, features in [