match lowering: test one or pattern at a time
This is a bit more opinionated than the previous PRs. On the face of it this is less efficient and more complex than before, but I personally found the loop that digs into `leaf_candidates` on each iteration very confusing. Instead this does "generate code for this or-pattern" then "generate further code for each branch if needed" in two steps.
Incidentally this way we don't _require_ or patterns to be sorted at the end. It's still an important optimization but I find it clearer to not rely on it for correctness.
r? `@matthewjasper`
Convert `delayed_bug`s to `bug`s.
I have a suspicion that quite a few delayed bug paths are impossible to reach, so I did an experiment.
I converted every `delayed_bug` to a `bug`, ran the full test suite, then converted back every `bug` that was hit. A surprising number were never hit.
This is too dangerous to merge. Increased coverage (fuzzing or a crater run) would likely hit more cases. But it might be useful for people to look at and think about which paths are genuinely unreachable.
r? `@ghost`
match lowering: simplify empty candidate selection
In match lowering, `match_simplified_candidates` is tasked with removing candidates that are fully matched and linking them up properly. The code that does that was needlessly complicated; this PR simplifies it.
The overall change isn't big but I split it up into tiny commits to convince myself that I was correctly preserving behavior. The test changes are all due to the first commit. Let me know if you'd prefer me to split up the PR to make reviewing easier.
r? `@matthewjasper`
I have a suspicion that quite a few delayed bug paths are impossible to
reach, so I did an experiment.
I converted every `delayed_bug` to a `bug`, ran the full test suite,
then converted back every `bug` that was hit. A surprising number were
never hit.
The next commit will convert some more back, based on human judgment.
The moment we get a candidate without guard, the return block becomes a
fresh block linked to nothing. So we can keep assigning a fresh block
every iteration to reuse the `next_prebinding` logic.
This mostly works well, and eliminates a couple of delayed bugs.
One annoying thing is that we should really also add an
`ErrorGuaranteed` to `proc_macro::bridge::LitKind::Err`. But that's
difficult because `proc_macro` doesn't have access to `ErrorGuaranteed`,
so we have to fake it.
match lowering: simplify block creation
Match lowering was doing complicated things with block creation. As far as I can tell it was trying to avoid creating unneeded blocks, but of the three places that start out with `otherwise = &mut None`, two of them called `otherwise.unwrap_or_else(|| self.cfg.start_new_block())` anyway. As far as I can tell the only place where this PR makes a difference is in `lower_match_tree`, which did indeed sometimes avoid creating the unreachable final block + FakeRead. Unless this is important I propose we do the naive thing instead.
I have not checked all the graph isomorphisms by hand, but at a glance the test diff looks sensible.
r? `@matthewjasper`
Make `min_exhaustive_patterns` match `exhaustive_patterns` better
Split off from https://github.com/rust-lang/rust/pull/120742.
There remained two edge cases where `min_exhaustive_patterns` wasn't behaving like `exhaustive_patterns`. This fixes them, and tests the feature in a bunch more cases. I essentially went through all uses of `exhaustive_patterns` to see which ones would be interesting to compare between the two features.
r? `@compiler-errors`
Rollup of 9 pull requests
Successful merges:
- #119592 (resolve: Unload speculatively resolved crates before freezing cstore)
- #120103 (Make it so that async-fn-in-trait is compatible with a concrete future in implementation)
- #120206 (hir: Make sure all `HirId`s have corresponding HIR `Node`s)
- #120214 (match lowering: consistently lower bindings deepest-first)
- #120688 (GVN: also turn moves into copies with projections)
- #120702 (docs: also check the inline stmt during redundant link check)
- #120727 (exhaustiveness: Prefer "`0..MAX` not covered" to "`_` not covered")
- #120734 (Add `SubdiagnosticMessageOp` as a trait alias.)
- #120739 (improve pretty printing for associated items in trait objects)
r? `@ghost`
`@rustbot` modify labels: rollup
match lowering: consistently lower bindings deepest-first
Currently when lowering match expressions to MIR, we do a funny little dance with the order of bindings. I attempt to explain it in the third commit: we handle refutable (i.e. needing a test) patterns differently than irrefutable ones. This leads to inconsistencies, as reported in https://github.com/rust-lang/rust/issues/120210. The reason we need a dance at all is for situations like:
```rust
fn foo1(x: NonCopyStruct) {
let y @ NonCopyStruct { copy_field: z } = x;
// the above should turn into
let z = x.copy_field;
let y = x;
}
```
Here the `y ```````@```````` binding will move out of `x`, so we need to copy the field first.
I believe that the inconsistency came about when we fixed https://github.com/rust-lang/rust/issues/69971, and didn't notice that the fix didn't extend to refutable patterns. My guess then is that ordering bindings by "deepest-first, otherwise source order" is a sound choice. This PR implements that (at least I hope, match lowering is hard to follow 🥲).
Fixes https://github.com/rust-lang/rust/issues/120210
r? ```````@oli-obk``````` since you merged the original fix to https://github.com/rust-lang/rust/issues/69971
cc ```````@matthewjasper```````
Borrow check inline const patterns
Add type annotations to MIR so that borrowck can pass constraints from inline constants in patterns to the containing function.
Also enables some inline constant pattern tests that were fixed by the THIR unsafeck stabilization.
cc #76001
Use `zip_eq` to enforce that things being zipped have equal sizes
Some `zip`s are best enforced to be equal, since size mismatches suggest deeper bugs in the compiler.
