Some small nits to the borrowck suggestions for mutating a map through index
1. Suggesting users to either use `.insert` or `.get_mut` (which do totally different things) can be a bit of a footgun, so let's make that a bit more nuanced.
2. I find the suggestion of `.get_mut(|val| { *val = whatever; })` to be a bit awkward. I changed this to be an if-let instead.
3. Fix a bug which was suppressing the structured suggestion for some mutations via the index operator on `HashMap`/`BTreeMap`.
r? estebank or reassign
borrowck diagnostics: make `add_move_error_suggestions` use the HIR rather than `SourceMap`
This PR aims to fix#132806 by rewriting `add_move_error_suggestions`[^1]. Previously, it manually scanned the source text to find a leading `&`, which isn't always going to produce a correct result (see: that issue). Admittedly, the HIR visitor in this PR introduces a lot of boilerplate, but hopefully the logic at its core isn't too complicated (I go over it in the comments). I also tried a simpler version that didn't use a HIR visitor and suggested adding `ref` always, but the `&ref x` suggestions really didn't look good. As a bonus for the added complexity though, it's now able to produce nice `&`-removing suggestions in more cases.
I tried to do this such that it avoids edition-dependent checks and its suggestions can be applied together with those from the match ergonomics 2024 migration lint. I haven't added tests for that since the details of match ergonomics 2024 are still being sorted out, but I can try if desired once that's finalized.
[^1]: In brief, it fires on patterns where users try to bind by-value in such a way that moves out of a reference to a non-Copy type (including slice references with non-copy elements). The suggestions are to change the binding's mode to be by-reference, either by removing[^2] an enclosing `&`/`&mut` or adding `ref` to the binding.
[^2]: Incidentally, I find the terminology of "consider removing the borrow" a bit confusing for a suggestion to remove a `&` pattern in order to make bindings borrow rather than move. I'm not sure what a good, concise way to explain that would be though, and that should go in a separate PR anyway.
- add a FIXME when looking for the region variance of unexpected regions
- drive-by: fix a doc comment link
- drive-by: simplify the variance match using exported variants instead
This context struct will hold data to help creating localized
constraints:
- the live regions, with the shape matching a CFG walk, indexed per
point
- the variance of these live regions, represented as the direction we'll
add the appropriate
We also add this structure to the mir typeck to record liveness data,
and make it responsible for localized constraint creation.
Avoid ICE in borrowck
Provide a fallback in `best_blame_constraint` when `find_constraint_paths_between_regions` doesn't have a result. This code is due a rework to avoid the letf-over `unwrap()`, but avoids the ICE caused by the repro.
Fix#133252.
Begin to implement type system layer of unsafe binders
Mostly TODOs, but there's a lot of match arms that are basically just noops so I wanted to split these out before I put up the MIR lowering/projection part of this logic.
r? oli-obk
Tracking:
- https://github.com/rust-lang/rust/issues/130516
cleanup `TypeVerifier`
We should merge it with the `TypeChecker` as we no longer bail in cases where it encounters an error since #111863.
It's quite inconsistent whether a check lives in the verifier or the `TypeChecker`, so this feels like a quite impactful cleanup. I expect that for this we may want to change the `TypeChecker` to also be a MIR visitor 🤔 this is non-trivial so I didn't fully do it in this PR.
Best reviewed commit by commit.
r? `@compiler-errors` feel free to reassign however
Foundations of location-sensitive polonius
I'd like to land the prototype I'm describing in the [polonius project goal](https://github.com/rust-lang/rust-project-goals/issues/118). It still is incomplete and naive and terrible but it's working "well enough" to consider landing.
I'd also like to make review easier by not opening a huge PR, but have a couple small-ish ones (the +/- line change summary of this PR looks big, but >80% is moving datalog to a single place).
This PR starts laying the foundation for that work:
- it refactors and collects 99% of the old datalog fact gen, which was spread around everywhere, into a single dedicated module. It's still present at 3 small places (one of which we should revert anyways) that are kinda deep within localized components and are not as easily extractable into the rest of fact gen, so it's fine for now.
- starts introducing the localized constraints, the building blocks of the naive way of implementing the location-sensitive analysis in-tree, which is roughly sketched out in https://smallcultfollowing.com/babysteps/blog/2023/09/22/polonius-part-1/ and https://smallcultfollowing.com/babysteps/blog/2023/09/29/polonius-part-2/ but with a different vibe than per-point environments described in these posts, just `r1@p: r2@q` constraints.
- sets up the skeleton of generating these localized constraints: converting NLL typeck constraints, and creating liveness constraints
- introduces the polonius dual to NLL MIR to help development and debugging. It doesn't do much currently but is a way to see these localized constraints: it's an NLL MIR dump + a dumb listing of the constraints, that can be dumped with `-Zdump-mir=polonius -Zpolonius=next`. Its current state is not intended to be a long-term thing, just for testing purposes -- I will replace its contents in the future with a different approach (an HTML+js file where we can more easily explore/filter/trace these constraints and loan reachability, have mermaid graphs of the usual graphviz dumps, etc).
I've started documenting the approach in this PR, I'll add more in the future. It's quite simple, and should be very clear when more constraints are introduced anyways.
r? `@matthewjasper`
Best reviewed per commit so that the datalog move is less bothersome to read, but if you'd prefer we separate that into a different PR, I can do that (and michael has offered to review these more mechanical changes if it'd help).
Provide a fallback in `best_blame_constraint` when `find_constraint_paths_between_regions` doesn't have a result. This code is due a rework to avoid the letf-over `unwrap()`, but avoids the ICE caused by the repro.
Fix#133252.
handle member constraints directly in the mir type checker
cleaner, faster, easier to change going forward :> fixes#109654
r? `@oli-obk` `@compiler-errors`
cleanup region handling: add `LateParamRegionKind`
The second commit is to enable a split between `BoundRegionKind` and `LateParamRegionKind`, by avoiding `BoundRegionKind` where it isn't necessary.
The third comment then adds `LateParamRegionKind` to avoid having the same late-param region for separate bound regions. This fixes#124021.
r? `@compiler-errors`
