add a test for strict_optional

Author: JelleZijlstra

test-data/unit/check-class-namedtuple.test

@@ -424,6 +424,26 @@ class UserDefined(NamedTuple):
 
 reveal_type(UserDefined())  # E: Revealed type is 'Tuple[__main__.Default, fallback=__main__.UserDefined]'
 reveal_type(UserDefined(Default()))  # E: Revealed type is 'Tuple[__main__.Default, fallback=__main__.UserDefined]'
+UserDefined(1)  # E: Argument 1 to "UserDefined" has incompatible type "int"; expected "Default"
+
+[builtins fixtures/list.pyi]
+
+[case testNewNamedTupleWithDefaultsStrictOptional]
+# flags: --fast-parser --strict-optional --python-version 3.6
+from typing import List, NamedTuple, Optional
+
+class HasNone(NamedTuple):
+    x: int
+    y: Optional[int] = None
+
+reveal_type(HasNone(1))  # E: Revealed type is 'Tuple[builtins.int, Union[builtins.int, builtins.None], fallback=__main__.HasNone]'
+HasNone(None)  # E: Argument 1 to "HasNone" has incompatible type None; expected "int"
+HasNone(1, y=None)
+HasNone(1, y=2)
+
+class CannotBeNone(NamedTuple):
+    x: int
+    y: int = None  # E: Incompatible types in assignment (expression has type None, variable has type "int")
 
 [builtins fixtures/list.pyi]