internal: clean up getfslineno (#6656)

testing/code/test_source.py

@@ -524,6 +524,14 @@ def test_getfslineno() -> None:
     B.__name__ = "B2"
     assert getfslineno(B)[1] == -1
 
+    co = compile("...", "", "eval")
+    assert co.co_filename == ""
+
+    if hasattr(sys, "pypy_version_info"):
+        assert getfslineno(co) == ("", -1)
+    else:
+        assert getfslineno(co) == ("", 0)
+
 
 def test_code_of_object_instance_with_call() -> None:
     class A: