Enable support for PEP 526 annotated assignments (#84)

Without this change, code with annotated assignments is crashing pyflakes with
an attribute error (`object has no attribute 'ANNASSIGN'`).

Test plan: new tests introduced conforming to behavior described in the PEP.

1 files changed, 61 insertions, 0 deletions

diff --git a/pyflakes/test/test_other.py b/pyflakes/test/test_other.py
index 109bc66..6f02001 100644
--- a/pyflakes/test/test_other.py
+++ b/pyflakes/test/test_other.py
@@ -1808,3 +1808,64 @@ class TestAsyncStatements(TestCase):
         mom = 'mom'
         f'{hi} {mom}'
         ''')
+
+    @skipIf(version_info < (3, 6), 'new in Python 3.6')
+    def test_variable_annotations(self):
+        self.flakes('''
+        name: str
+        age: int
+        ''')
+        self.flakes('''
+        name: str = 'Bob'
+        age: int = 18
+        ''')
+        self.flakes('''
+        class C:
+            name: str
+            age: int
+        ''')
+        self.flakes('''
+        class C:
+            name: str = 'Bob'
+            age: int = 18
+        ''')
+        self.flakes('''
+        def f():
+            name: str
+            age: int
+        ''')
+        self.flakes('''
+        def f():
+            name: str = 'Bob'
+            age: int = 18
+            foo: not_a_real_type = None
+        ''', m.UnusedVariable, m.UnusedVariable, m.UnusedVariable)
+        self.flakes('''
+        def f():
+            name: str
+            print(name)
+        ''', m.UndefinedName)
+        self.flakes('''
+        foo: not_a_real_type
+        ''', m.UndefinedName)
+        self.flakes('''
+        foo: not_a_real_type = None
+        ''', m.UndefinedName)
+        self.flakes('''
+        class C:
+            foo: not_a_real_type
+        ''', m.UndefinedName)
+        self.flakes('''
+        class C:
+            foo: not_a_real_type = None
+        ''', m.UndefinedName)
+        self.flakes('''
+        def f():
+            class C:
+                foo: not_a_real_type
+        ''', m.UndefinedName)
+        self.flakes('''
+        def f():
+            class C:
+                foo: not_a_real_type = None
+        ''', m.UndefinedName)