Start working with mypy

parso/cache.py

@@ -7,10 +7,6 @@ import shutil
 import platform
 import logging
 import warnings
-
-try:
-    import cPickle as pickle
-except:
 import pickle
 
 from parso.file_io import FileIO

parso/normalizer.py

@@ -149,8 +149,8 @@ class Issue(object):
 
 
 class Rule(object):
-    code = None
-    message = None
+    code: int
+    message: str
 
     def __init__(self, normalizer):
         self._normalizer = normalizer

parso/tree.py

@@ -23,7 +23,7 @@ class NodeOrLeaf(object):
     The base class for nodes and leaves.
     """
     __slots__ = ()
-    type = None
+    type: str
     '''
     The type is a string that typically matches the types of the grammar file.
     '''
@@ -257,7 +257,6 @@ class BaseNode(NodeOrLeaf):
     A node has children, a type and possibly a parent node.
     """
     __slots__ = ('children', 'parent')
-    type = None
 
     def __init__(self, children):
         self.children = children

setup.cfg

@@ -10,3 +10,16 @@ ignore =
   E226,
   # line break before binary operator
   W503,
+
+
+[mypy]
+disallow_subclassing_any = True
+
+# Avoid creating future gotchas emerging from bad typing
+warn_redundant_casts = True
+warn_unused_ignores = True
+warn_return_any = True
+warn_unused_configs = True
+warn_unreachable = True
+
+strict_equality = True

setup.py

@@ -12,7 +12,8 @@ __AUTHOR_EMAIL__ = 'davidhalter88@gmail.com'
 
 readme = open('README.rst').read() + '\n\n' + open('CHANGELOG.rst').read()
 
-setup(name='parso',
+setup(
+    name='parso',
     version=parso.__version__,
     description='A Python Parser',
     author=__AUTHOR__,
@@ -49,5 +50,9 @@ setup(name='parso',
             'pytest<6.0.0',
             'docopt',
         ],
+        'qa': [
+            'flake8==3.8.3',
+            'mypy==0.782',
+        ],
     },
 )