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5baf1e13f5
match lowering: sort `Eq` candidates in the failure case too
This is a slight tweak to MIR gen of matches. Take a match like:
```rust
match (s, flag) {
("a", _) if foo() => 1,
("b", true) => 2,
("a", false) => 3,
(_, true) => 4,
_ => 5,
}
```
If we switch on `s == "a"`, the first candidate matches, and we learn almost nothing about the second candidate. So there's a choice:
1. (what we do today) stop sorting candidates, keep the "b" case grouped with everything below. This could allow us to be clever here and test on `flag == true` next.
2. (what this PR does) sort "b" into the failure case. The "b" will be alone (fewer opportunities for picking a good test), but that means the two "a" cases require a single test.
Today, we aren't clever in which tests we pick, so this is an unambiguous win. In a future where we pick tests better, idk. Grouping tests as much as possible feels like a generally good strategy.
This was proposed in https://github.com/rust-lang/rust/issues/29623 (9 years ago :D)
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| assembly | ||
| auxiliary | ||
| codegen | ||
| codegen-units | ||
| coverage | ||
| coverage-run-rustdoc | ||
| debuginfo | ||
| incremental | ||
| mir-opt | ||
| pretty | ||
| run-make | ||
| run-make-fulldeps | ||
| run-pass-valgrind | ||
| rustdoc | ||
| rustdoc-gui | ||
| rustdoc-js | ||
| rustdoc-js-std | ||
| rustdoc-json | ||
| rustdoc-ui | ||
| ui | ||
| ui-fulldeps | ||
| COMPILER_TESTS.md | ||