Add typings

immutabledict/__init__.py

@@ -1,10 +1,27 @@
+import sys
 from collections import OrderedDict
-from collections.abc import Mapping
+from typing import Dict, TypeVar
+
+if sys.version_info >= (3, 7):
+    from typing import Mapping
+else:  # pragma: no cover
+    from collections.abc import Mapping as _BaseMapping
+
+    class _MappingMeta(type):
+        def __getitem__(self, *args):
+            return _BaseMapping
+
+    class Mapping(metaclass=_MappingMeta):
+        pass
+
 
 __version__ = "1.2.0"
 
+_K = TypeVar("_K")
+_V = TypeVar("_V")
+
 
-class immutabledict(Mapping):
+class immutabledict(Mapping[_K, _V]):
     """
     An immutable wrapper around dictionaries that implements the complete :py:class:`collections.Mapping`
     interface. It can be used as a drop-in replacement for dictionaries where immutability is desired.
@@ -26,7 +43,7 @@ def __getitem__(self, key):
     def __contains__(self, key):
         return key in self._dict
 
-    def copy(self, **add_or_replace):
+    def copy(self, **add_or_replace: Dict[_K, _V]) -> "immutabledict[_K, _V]":
         return self.__class__(self, **add_or_replace)
 
     def __iter__(self):

pyproject.toml

@@ -23,7 +23,9 @@ black = {version = "^20.8b1", python = "^3.6"}
 pytest = "^6.2"
 isort = {version = "^5.8", python = "^3.6"}
 pytest-cov = "^2.11"
+mypy = "^0.812"
+tox = "^3.23.0"
 
 [build-system]
-requires = ["poetry>=0.12"]
+requires = ["poetry>=1.1.5"]
 build-backend = "poetry.masonry.api"

tox.ini

@@ -0,0 +1,9 @@
+[tox]
+isolated_build = true
+envlist = py36,py37,py38,py39
+
+[testenv]
+whitelist_externals = poetry
+commands =
+    poetry install -v
+    poetry run pytest tests/