[Core] Type check ObjectRef (#9856)

* Type check ObjectRef

* Bug fix

* Port typing tests to bazel test

python/ray/tests/test_typing.py

@@ -0,0 +1,26 @@
+import sys
+import os
+
+import mypy.api as mypy_api
+import pytest
+
+TYPING_TEST_DIRS = os.path.join(os.path.dirname(__file__), "typing_files")
+
+
+def test_typing_good():
+    script = os.path.join(TYPING_TEST_DIRS, "check_typing_good.py")
+    msg, _, status_code = mypy_api.run([script])
+    assert status_code == 0, msg
+
+
+def test_typing_bad():
+    script = os.path.join(TYPING_TEST_DIRS, "check_typing_bad.py")
+    msg, _, status_code = mypy_api.run([script])
+    assert status_code == 1, msg
+
+
+if __name__ == "__main__":
+    # Make subprocess happy in bazel.
+    os.environ["LC_ALL"] = "en_US.UTF-8"
+    os.environ["LANG"] = "en_US.UTF-8"
+    sys.exit(pytest.main(["-v", __file__]))