The version of `flake8` was too old to support with Python 3.12 -- there
is new F-string support that caused false positives sadly. The updated
version has fixes for all of these.
This in turn updates codespell which has picked up several new fixes
that actually fire in our code, so also fix everything. While we don't
do more in-depth updates to old proposals, similar to simply fixing
broken links, fixing automatically detected typos seems scalable and
fine.
All edits were automatically generated here.
The design of choice types expects the declaration of an alternative to match the usage: if an alternative is declared as `None`, then it should be used as `None` not `None()`, and if it is declared as `None()` then it should be used as `None()` not `None`. Update explorer to match.
Also clean up the handling of choice types and alternative values a little in general, by moving away from identifying choice types and alternatives as strings and towards identifying them symbolically.
Closes#2422
In particular, this means that a type can implement `ImplicitAs(Type)` and have values of that type behave like types.
This implies that `()` and `{}` are no longer types. They are now values whose type is the result of converting `()` or `{}` to type `Type`, as has been discussed recently and seems to be the supported direction. This fixes various cases where these types were previously mishandled.
When checking for control flow falling off a function after a `match`, determine whether it's possible for no case to have matched. Using the same implementation, also detect whether `case`s in a `match` are unreachable.
For now, the implementation never considers a match against specific values for any type other than tuples, alternatives, and `bool` to be exhaustive. In particular, matching against the sole value `{}` of type `{}` is not considered exhaustive. This is probably best left until explorer supports matching on struct and maybe class types more generally.
This implementation closely follows the algorithm described in the paper [Warnings for pattern matching](http://moscova.inria.fr/~maranget/papers/warn/warn.pdf) by Luc Maranget. Various optimizations are possible, such as reducing the amount of copying done, but for the purposes of explorer, comprehensibility is being favored over efficiency.
The problem is, perhaps surprisingly, co-NP-hard (by reduction to the tautology problem for disjunctive normal form, which is in turn dual to the satisfaction problem for conjunctive normal form, which is well-known to be NP-hard). The algorithm is therefore exponential-time in the worst case, but seems to be well-studied and performs well enough on non-pathological examples. Nonetheless, a depth limit has been imposed to prevent pathological examples such as those generated by a fuzzer from causing long runtimes.
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Chandler Carruth
Richard SmithandJon Ross-Perkins