add generics type parameters to ImmutableMultiDict

Slice of encode#1403

starlette/datastructures.py

@@ -11,6 +11,11 @@
 Address = namedtuple("Address", ["host", "port"])
 
 
+_T = typing.TypeVar("_T")
+_KT = typing.TypeVar("_KT")  # key type
+_VT_co = typing.TypeVar("_VT_co", covariant=True)  # value type for covariant containers
+
+
 class URL:
     def __init__(
         self, url: str = "", scope: Scope = None, **components: typing.Any
@@ -230,13 +235,15 @@ def __str__(self) -> str:
         return ", ".join(repr(item) for item in self)
 
 
-class ImmutableMultiDict(typing.Mapping):
+class ImmutableMultiDict(typing.Mapping[_KT, _VT_co]):
+    _dict: typing.Dict[_KT, _VT_co]
+
     def __init__(
         self,
         *args: typing.Union[
-            "ImmutableMultiDict",
-            typing.Mapping,
-            typing.List[typing.Tuple[typing.Any, typing.Any]],
+            "ImmutableMultiDict[_KT, _VT_co]",
+            typing.Mapping[_KT, _VT_co],
+            typing.Sequence[typing.Tuple[_KT, _VT_co]],
         ],
         **kwargs: typing.Any,
     ) -> None:
@@ -246,7 +253,7 @@ def __init__(
         if kwargs:
             value = (
                 ImmutableMultiDict(value).multi_items()
-                + ImmutableMultiDict(kwargs).multi_items()
+                + ImmutableMultiDict(kwargs).multi_items()  # type: ignore[operator]
             )
 
         if not value:
@@ -266,33 +273,43 @@ def __init__(
         self._dict = {k: v for k, v in _items}
         self._list = _items
 
-    def getlist(self, key: typing.Any) -> typing.List[typing.Any]:
+    def getlist(self, key: typing.Any) -> typing.List[_VT_co]:
         return [item_value for item_key, item_value in self._list if item_key == key]
 
-    def keys(self) -> typing.KeysView:
+    def keys(self) -> typing.KeysView[_KT]:
         return self._dict.keys()
 
-    def values(self) -> typing.ValuesView:
+    def values(self) -> typing.ValuesView[_VT_co]:
         return self._dict.values()
 
-    def items(self) -> typing.ItemsView:
+    def items(self) -> typing.ItemsView[_KT, _VT_co]:
         return self._dict.items()
 
-    def multi_items(self) -> typing.List[typing.Tuple[str, str]]:
+    def multi_items(self) -> typing.List[typing.Tuple[_KT, _VT_co]]:
         return list(self._list)
 
-    def get(self, key: typing.Any, default: typing.Any = None) -> typing.Any:
+    @typing.overload
+    def get(self, key: _KT) -> _VT_co:
+        ...  # pragma: no cover
+
+    @typing.overload
+    def get(
+        self, key: _KT, default: typing.Optional[typing.Union[_VT_co, _T]] = ...
+    ) -> typing.Union[_VT_co, _T]:
+        ...  # pragma: no cover
+
+    def get(self, key: _KT, default: typing.Any = None) -> typing.Any:
         if key in self._dict:
             return self._dict[key]
         return default
 
-    def __getitem__(self, key: typing.Any) -> str:
+    def __getitem__(self, key: _KT) -> _VT_co:
         return self._dict[key]
 
     def __contains__(self, key: typing.Any) -> bool:
         return key in self._dict
 
-    def __iter__(self) -> typing.Iterator[typing.Any]:
+    def __iter__(self) -> typing.Iterator[_KT]:
         return iter(self.keys())
 
     def __len__(self) -> int:
@@ -309,7 +326,7 @@ def __repr__(self) -> str:
         return f"{class_name}({items!r})"
 
 
-class MultiDict(ImmutableMultiDict):
+class MultiDict(ImmutableMultiDict[typing.Any, typing.Any]):
     def __setitem__(self, key: typing.Any, value: typing.Any) -> None:
         self.setlist(key, [value])