This serves two purposes.
First, they're additional tests that stable Rust behavior hasn't been
messed with. There's plenty of other pattern tests, so this is less
important, but these at least are targeted at what's being changed.
Second, this helps document exactly where the new rulesets agree and
disagree with stable pattern typing. This will be especially important
after the new rules for old editions are updated, since they need to be
strictly more permissive; any patterns well-typed on stable should also
be well-typed with the same resultant bindings on the (upcoming) new new
old-edition rules.
The unusual test ordering on `borrowck-errors.rs` and
`ref-binding-on-inh-ref-errors.rs` are to hopefully reduce how much
adding new tests will mess with line numbers in their stderr.
I think the diagnostic could use some work, but it's more helpful than
the alternative. The previous error was misleading, since it ignored the
inherited reference altogether.
These come directly from the "Compare" tab of Typing Rust Patterns,
though they had to be split across multiple files. They're not
comprehensive, but they do provide some previously-missing coverage and
are easier to check against the spec. Possibly they should be split up
some more, since `pattern-errors.rs` is getting a bit unwieldy, but I'm
not sure how best to go about that.
The debug assertion ensuring that the pattern mutability cap holds
assumes the presence of Rule 3, so it now checks for that. I
considered going back to only tracking the mutability cap when Rule 3
is present, but since the mutability cap is used in Rule 5's
implementation too, the debug assertion would still need to check
which typing rules are present.
This also required some changes to tests:
- `ref_pat_eat_one_layer_2021.rs` had a test for Rule 3; I'll be
handling tests for earlier editions in a later commit, so as a stopgap
I've #[cfg]ed it out.
- One test case had to be moved from `well-typed-edition-2024.rs` to
`borrowck-errors.rs` in order to get borrowck to run on it and emit an
error.
This only includes previously existing tests (with a couple duplicates
removed). I plan on adding more comprarisons where the rules differ
once I've updated the pattern typing rules. I also haven't touched the
tests for new rules in old editions; I'll see how best to handle that
once those rules are updated as well.
