Use variable annotations (#10723)

* Run com2ann

* manual fixes (mainly None defaults)

* manual fixes (mainly stringifying types)

* manual fixes (more default types)

* and some type ignores

* run darker to appease flake8

* fix tests part 1 of ???

* fix tests part 2 of ???

* fix tests part 3 of ???

* fix tests part 4 of ???

Co-authored-by: hauntsaninja <>

mypy/applytype.py

@@ -75,7 +75,7 @@ def apply_generic_arguments(
     types = get_proper_types(orig_types)
 
     # Create a map from type variable id to target type.
-    id_to_type = {}  # type: Dict[TypeVarId, Type]
+    id_to_type: Dict[TypeVarId, Type] = {}
 
     for tvar, type in zip(tvars, types):
         assert not isinstance(type, PartialType), "Internal error: must never apply partial type"

mypy/argmap.py

@@ -23,8 +23,8 @@ def map_actuals_to_formals(actual_kinds: List[int],
     argument type with the given index.
     """
     nformals = len(formal_kinds)
-    formal_to_actual = [[] for i in range(nformals)]  # type: List[List[int]]
-    ambiguous_actual_kwargs = []  # type: List[int]
+    formal_to_actual: List[List[int]] = [[] for i in range(nformals)]
+    ambiguous_actual_kwargs: List[int] = []
     fi = 0
     for ai, actual_kind in enumerate(actual_kinds):
         if actual_kind == nodes.ARG_POS:
@@ -112,7 +112,7 @@ def map_formals_to_actuals(actual_kinds: List[int],
                                               formal_names,
                                               actual_arg_type)
     # Now reverse the mapping.
-    actual_to_formal = [[] for _ in actual_kinds]  # type: List[List[int]]
+    actual_to_formal: List[List[int]] = [[] for _ in actual_kinds]
     for formal, actuals in enumerate(formal_to_actual):
         for actual in actuals:
             actual_to_formal[actual].append(formal)
@@ -145,7 +145,7 @@ def __init__(self) -> None:
         # Next tuple *args index to use.
         self.tuple_index = 0
         # Keyword arguments in TypedDict **kwargs used.
-        self.kwargs_used = set()  # type: Set[str]
+        self.kwargs_used: Set[str] = set()
 
     def expand_actual_type(self,
                            actual_type: Type,

mypy/binder.py

@@ -32,7 +32,7 @@ class Frame:
     """
 
     def __init__(self) -> None:
-        self.types = {}  # type: Dict[Key, Type]
+        self.types: Dict[Key, Type] = {}
         self.unreachable = False
 
         # Should be set only if we're entering a frame where it's not
@@ -69,7 +69,7 @@ class A:
     """
     # Stored assignments for situations with tuple/list lvalue and rvalue of union type.
     # This maps an expression to a list of bound types for every item in the union type.
-    type_assignments = None  # type: Optional[Assigns]
+    type_assignments: Optional[Assigns] = None
 
     def __init__(self) -> None:
         # The stack of frames currently used.  These map
@@ -85,21 +85,21 @@ def __init__(self) -> None:
         # the end of the frame or by a loop control construct
         # or raised exception. The last element of self.frames
         # has no corresponding element in this list.
-        self.options_on_return = []  # type: List[List[Frame]]
+        self.options_on_return: List[List[Frame]] = []
 
         # Maps literal_hash(expr) to get_declaration(expr)
         # for every expr stored in the binder
-        self.declarations = {}  # type: Dict[Key, Optional[Type]]
+        self.declarations: Dict[Key, Optional[Type]] = {}
         # Set of other keys to invalidate if a key is changed, e.g. x -> {x.a, x[0]}
         # Whenever a new key (e.g. x.a.b) is added, we update this
-        self.dependencies = {}  # type: Dict[Key, Set[Key]]
+        self.dependencies: Dict[Key, Set[Key]] = {}
 
         # Whether the last pop changed the newly top frame on exit
         self.last_pop_changed = False
 
-        self.try_frames = set()  # type: Set[int]
-        self.break_frames = []  # type: List[int]
-        self.continue_frames = []  # type: List[int]
+        self.try_frames: Set[int] = set()
+        self.break_frames: List[int] = []
+        self.continue_frames: List[int] = []
 
     def _add_dependencies(self, key: Key, value: Optional[Key] = None) -> None:
         if value is None: