detect undefined name of variable defined by AnnAssign (#729)

Author: asottile

pyflakes/checker.py

@@ -2265,7 +2265,6 @@ def EXCEPTHANDLER(self, node):
             self.scope[node.name] = prev_definition
 
     def ANNASSIGN(self, node):
-        self.handleNode(node.target, node)
         self.handleAnnotation(node.annotation, node)
         # If the assignment has value, handle the *value* now.
         if node.value:
@@ -2274,6 +2273,7 @@ def ANNASSIGN(self, node):
                 self.handleAnnotation(node.value, node)
             else:
                 self.handleNode(node.value, node)
+        self.handleNode(node.target, node)
 
     def COMPARE(self, node):
         left = node.left

pyflakes/test/test_type_annotations.py

@@ -298,6 +298,11 @@ def g(t: 'T'): pass
         a: 'a: "A"'
         ''', m.ForwardAnnotationSyntaxError)
 
+    def test_variable_annotation_references_self_name_undefined(self):
+        self.flakes("""
+        x: int = x
+        """, m.UndefinedName)
+
     def test_TypeAlias_annotations(self):
         self.flakes("""
         from typing_extensions import TypeAlias