On Wed, Oct 28, 2020 at 12:48 PM Emily Bowman <silverback...@gmail.com>
wrote:
> On Wed, Oct 28, 2020 at 6:49 AM Jean Abou Samra <j...@abou-samra.fr>
> wrote:
>
>> where `impossible` raises AssertionError.
>>
>
> Reserving a common English word as a new keyword (whether fail or
> impossible) is the mother of all breaking changes. The syntactic sugar it
> provides is not only tiny, it's pretty much negative, since any message it
> could provide would be too generic to be of much use, versus raising your
> own relevant exception message.
>
Indeed, especially when you can write this once at the top of your module,
or in a utils module in a larger package:
def unreachable():
raise AssertionError
and then Jean's example can be spelled:
match args:
case [Point2d(x, y)]:
...
case ...:
...
case ...:
...
case ...:
...
case _:
unreachable()
Same benefit of a plain English word, identical behavior, very very tiny
downside of two parentheses and a two-line function definition, and zero
breakage or compatibility issues.
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