On Sat, Jul 11, 2020 at 5:58 PM Chris Angelico <rosuav@gmail.com> wrote:

Hang on. Matching happens before assignment, so this should use the
previous value of x for the matching. At least, that's my
understanding. If you do something like:

case Point(x, 2):

it won't assign x unless the second coordinate is 2, right?

Good catch. That's actually undefined -- we want to let the optimizer have some leeway in how to generate  the best code for matching. See https://www.python.org/dev/peps/pep-0622/#performance-considerations

Currently it doesn't optimize all that much -- it just processes patterns from left to right:

```

>>> match Point(3, 3):
...   case Point(x, 42): pass
...
>>> print(x)
3
>>>

```