Thank you, but I don't think this is a duplicate of issue42717. This crash is probably caused by the parameter "target" of Thread. "Target" accept the "callable object". Defaults to None. In this program, it's assigned to a "Int object". I think a pre-checking of parameter for such error should be added. 



Minimal test case should be:
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import threading
for i in range(10):
    t = threading.Thread(target=1, daemon=True).start()  
================================= 



In fact, I try this one. No loop, It sometime crashes the parser.(not always, twice in ten times)
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import threading
t = threading.Thread(target=1, daemon=True).start()
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