>>>>> def t() -> void:
.....     pass
..... 
thread 'main' panicked at 'called `Option::unwrap()` on a `None` value', src/libcore/option.rs:347:21
note: Run with `RUST_BACKTRACE=1` environment variable to display a backtrace.

>>> def t() -> void:
...     pass
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'void' is not defined