Do not parse default values as types

See python/typeshed#9501.

pytype/pyi/parser.py

@@ -161,6 +161,12 @@ def visit_Pyval(self, node):
     if node.type == "str" and not self.subscripted:
       return self.convert_late_annotation(node.value)
 
+  def visit_arg(self, node):
+    # Visit only the annotation, not the default (which may be a
+    # string but should not be interpreted as a type annotation).
+    if node.annotation is not None:
+      self.visit(node.annotation)
+
   def visit_Tuple(self, node):
     return tuple(node.elts)
 

pytype/pyi/parser_test.py

@@ -846,6 +846,13 @@ def test_params(self):
     self.check("def foo(x: int, y: str, z: bool,) -> int: ...",
                "def foo(x: int, y: str, z: bool) -> int: ...")
 
+  def test_defaults(self):
+    self.check("""
+      def f(x: int = 3, y: str = "y") -> None: ...
+    """, """
+      def f(x: int = ..., y: str = ...) -> None: ...
+    """)
+
   def test_star_params(self):
     self.check("def foo(*, x) -> str: ...")
     self.check("def foo(x: int, *args) -> str: ...")