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PiperOrigin-RevId: 683162424

pytype/abstract/function.py

@@ -1170,20 +1170,26 @@ def handle_typeguard(node, ret: _ReturnType, first_arg, ctx, func_name=None):
     )
     return None
   target = frame.lookup_name(target_name)
-  # Forward all the target's bindings to the current node, so we don't have
-  # visibility problems later.
-  target.PasteVariable(target, node)
-  old_data = set(target.data)
+
+  # Forward all the target's visible bindings to the current node. We're going
+  # to add new bindings soon, which would otherwise hide the old bindings, kinda
+  # like assigning the variable to a new value.
+  for b in target.Bindings(node):
+    target.PasteBinding(b, node)
+
+  # Add missing bindings to the target variable.
+  old_data = set(target.Data(node))
   new_instance = ret.instantiate_parameter(node, abstract_utils.T)
+  new_data = set(new_instance.data)
   for b in new_instance.bindings:
-    if b.data not in target.data:
+    if b.data not in old_data:
       target.PasteBinding(b, node)
 
   # Create a boolean return variable with True bindings for values that
   # originate from the type guard type and False for the rest.
   typeguard_return = ctx.program.NewVariable()
-  for b in target.bindings:
-    boolvals = {b.data not in old_data} | {b.data in new_instance.data}
+  for b in target.Bindings(node):
+    boolvals = {b.data not in old_data} | {b.data in new_data}
     for v in boolvals:
       typeguard_return.AddBinding(ctx.convert.bool_values[v], {b}, node)
   return typeguard_return

pytype/tests/test_typeguard.py

@@ -461,6 +461,76 @@ def f(x) -> TypeGuard[tuple[str, int]]:
         assert_type(e2, int)
     """)
 
+  def test_only_use_visible_bindings(self):
+    with self.DepTree([(
+        "foo.pyi",
+        """
+        from typing import TypeGuard
+        class Foo: ...
+        def isfoo(x: object) -> TypeGuard[Foo]: ...
+        """,
+    )]):
+      self.Check("""
+        import foo
+
+        value = 1
+        del value  # add "Deleted" binding for `value`
+        value = 2
+        if foo.isfoo(value):
+          print(value)  # "Deleted" binding should not be visible here
+      """)
+
+  def test_dont_hide_previous_bindings(self):
+    with self.DepTree([(
+        "foo.pyi",
+        """
+        from typing import TypeGuard
+        class Foo: ...
+        class Bar: ...
+        class Baz: ...
+        def isbar(x: object) -> TypeGuard[Bar]: ...
+        def isbaz(x: object) -> TypeGuard[Baz]: ...
+        """,
+    )]):
+      errors = self.CheckWithErrors("""
+        import foo
+
+        def takes_foo(x: foo.Foo):
+          pass
+
+        def test(x: foo.Foo):
+          is_bar = foo.isbar(x)
+          is_baz = foo.isbaz(x)
+          takes_foo(x)
+          reveal_type(x)  # reveal-type[e]
+      """)
+      # This documents a slightly incorrect type inference. Arguably `x` should
+      # just be `Foo` here.
+      self.assertErrorSequences(
+          errors, {"e": "Union[foo.Bar, foo.Baz, foo.Foo]"}
+      )
+
+  def test_type_guard_matches_input_type(self):
+    with self.DepTree([(
+        "foo.pyi",
+        """
+        from typing import TypeGuard
+        class Foo: ...
+        def isfoo(x: object) -> TypeGuard[Foo]: ...
+        """,
+    )]):
+      self.Check("""
+        import foo
+
+        class Test:
+          def __init__(self, value: foo.Foo):
+            if not foo.isfoo(value):
+              raise ValueError('"value" must be a Foo')
+            self.value = value
+
+        print(Test(foo.Foo()).value)  # .value must be defined here
+      """)
+
 
 if __name__ == "__main__":
   test_base.main()