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786c94a4eb
Lint `non_exhaustive_omitted_patterns` by columns
This is a rework of the `non_exhaustive_omitted_patterns` lint to make it more consistent. The intent of the lint is to help consumers of `non_exhaustive` enums ensure they stay up-to-date with all upstream variants. This rewrite fixes two cases we didn't handle well before:
First, because of details of exhaustiveness checking, the following wouldn't lint `Enum::C` as missing:
```rust
match Some(x) {
Some(Enum::A) => {}
Some(Enum::B) => {}
_ => {}
}
```
Second, because of the fundamental workings of exhaustiveness checking, the following would treat the `true` and `false` cases separately and thus lint about missing variants:
```rust
match (true, x) {
(true, Enum::A) => {}
(true, Enum::B) => {}
(false, Enum::C) => {}
_ => {}
}
```
Moreover, it would correctly not lint in the case where the pair is flipped, because of asymmetry in how exhaustiveness checking proceeds.
A drawback is that it no longer makes sense to set the lint level per-arm. This will silently break the lint for current users of it (but it's behind a feature gate so that's ok).
The new approach is now independent of the exhaustiveness algorithm; it's a separate pass that looks at patterns column by column. This is another of the motivations for this: I'm glad to move it out of the algorithm, it was akward there.
This PR is almost identical to https://github.com/rust-lang/rust/pull/111651. cc `@eholk` who reviewed it at the time. Compared to then, I'm more confident this is the right approach.
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| .. | ||
| rfc-0107-bind-by-move-pattern-guards | ||
| rfc-1014-stdout-existential-crisis | ||
| rfc-1445-restrict-constants-in-patterns | ||
| rfc-1623-static | ||
| rfc-1717-dllimport | ||
| rfc-1789-as-cell | ||
| rfc-1857-stabilize-drop-order | ||
| rfc-1937-termination-trait | ||
| rfc-2005-default-binding-mode | ||
| rfc-2008-non-exhaustive | ||
| rfc-2027-object-safe-for-dispatch | ||
| rfc-2091-track-caller | ||
| rfc-2093-infer-outlives | ||
| rfc-2126-crate-paths | ||
| rfc-2126-extern-absolute-paths | ||
| rfc-2151-raw-identifiers | ||
| rfc-2175-or-if-while-let | ||
| rfc-2294-if-let-guard | ||
| rfc-2302-self-struct-ctor | ||
| rfc-2306-convert-id | ||
| rfc-2361-dbg-macro | ||
| rfc-2396-target_feature-11 | ||
| rfc-2397-do-not-recommend | ||
| rfc-2421-unreserve-pure-offsetof-sizeof-alignof | ||
| rfc-2457-non-ascii-idents | ||
| rfc-2497-if-let-chains | ||
| rfc-2528-type-changing-struct-update | ||
| rfc-2565-param-attrs | ||
| rfc-2627-raw-dylib | ||
| rfc-2632-const-trait-impl | ||
| rfc-3348-c-string-literals | ||