Add method to get type of an Rvalue in StableMIR
Provide a method to StableMIR users to retrieve the type of an Rvalue operation. There were two possible implementation:
1. Create the logic inside stable_mir to process the type according to the Rvalue semantics, which duplicates the logic of `rustc_middle::mir::Rvalue::ty()`.
2. Implement the Rvalue translation from StableMIR back to internal representation, invoke the `rustc_middle::mir::Rvalue::ty()`, and translate the return value to StableMIR.
I chose the first one for now since the duplication was fairly small, and the option 2 would require way more work to translate everything back to rustc internal representation. If we eventually add those translations, we could easily swap to the option 2.
```@compiler-errors``` / ```@ouz-a``` Please let me know if you have any strong opinion here.
r? ```@compiler-errors```
compile-time evaluation: detect writes through immutable pointers
This has two motivations:
- it unblocks https://github.com/rust-lang/rust/pull/116745 (and therefore takes a big step towards `const_mut_refs` stabilization), because we can now detect if the memory that we find in `const` can be interned as "immutable"
- it would detect the UB that was uncovered in https://github.com/rust-lang/rust/pull/117905, which was caused by accidental stabilization of `copy` functions in `const` that can only be called with UB
When UB is detected, we emit a future-compat warn-by-default lint. This is not a breaking change, so completely in line with [the const-UB RFC](https://rust-lang.github.io/rfcs/3016-const-ub.html), meaning we don't need t-lang FCP here. I made the lint immediately show up for dependencies since it is nearly impossible to even trigger this lint without `const_mut_refs` -- the accidentally stabilized `copy` functions are the only way this can happen, so the crates that popped up in #117905 are the only causes of such UB (in the code that crater covers), and the three cases of UB that we know about have all been fixed in their respective crates already.
The way this is implemented is by making use of the fact that our interpreter is already generic over the notion of provenance. For CTFE we now use the new `CtfeProvenance` type which is conceptually an `AllocId` plus a boolean `immutable` flag (but packed for a more efficient representation). This means we can mark a pointer as immutable when it is created as a shared reference. The flag will be propagated to all pointers derived from this one. We can then check the immutable flag on each write to reject writes through immutable pointers.
I just hope perf works out.
Fix is_foreign_item for StableMIR instance
Change the implementation of `Instance::is_foreign_item` to directly query the compiler for the instance `def_id` instead of incorrectly relying on the conversion to `CrateItem`. I also added a method to check if the instance has body, since the function already existed and it just wasn't exposed via public APIs. This makes it much cheaper for the user to check if the instance has body.
## Background:
- In pull https://github.com/rust-lang/rust/pull/118524, I fixed the conversion from Instance to CrateItem to avoid the conversion if the instance didn't have a body available. This broke the `is_foreign_item`.
r? `@ouz-a`
Change the implementation of `Instance::is_foreign_item` to directly
query the compiler for the instance `def_id` instead of incorrectly
relying on the conversion to `CrateItem`.
Background:
- In pull https://github.com/rust-lang/rust/pull/118524, I fixed the
conversion from Instance to CrateItem to avoid the conversion if the
instance didn't have a body available. This broke the `is_foreign_item`.
Although, we would like to avoid crashes whenever
possible, and that's why I wanted to make this API fallible. It's
looking pretty hard to do proper validation.
I think many of our APIs will unfortunately depend on the user doing
the correct thing since at the MIR level we are working on,
we expect types to have been checked already.
The new structure encodes its invariant, which reduces the likelihood
of having an inconsistent representation. It is also more intuitive and
user friendly.
I encapsulated the structure for now in case we decide to change it back.
Add `pretty_terminator` to pretty stable-mir
~Because we don't have successors in `stable_mir` this is somewhat lacking but it's better than nothing~, also fixed bug(?) with `Opaque` which printed extra `"` when we try to print opaqued `String`.
**Edit**: Added successors so this covers Terminators as a whole.
r? `@celinval`
Add common trait for crate definitions
In stable mir, we specialize DefId, however some functionality is the same for every definition, such as def paths, and getting their crate. Use a trait to implement those.
Remove `PredicateKind::ClosureKind`
We don't need the `ClosureKind` predicate kind -- instead, `Fn`-family trait goals are left as ambiguous, and we only need to make progress on `FnOnce` projection goals for inference purposes.
This is similar to how we do confirmation of `Fn`-family trait and projection goals in the new trait solver, which also doesn't use the `ClosureKind` predicate.
Some hacky logic is added in the second commit so that we can keep the error messages the same.
Rollup of 5 pull requests
Successful merges:
- #117972 (Add VarDebugInfo to Stable MIR)
- #118109 (rustdoc-search: simplify `checkPath` and `sortResults`)
- #118110 (Document `DefiningAnchor` a bit more)
- #118112 (Don't ICE when ambiguity is found when selecting `Index` implementation in typeck)
- #118135 (Remove quotation from filename in stable_mir)
Failed merges:
- #118012 (Add support for global allocation in smir)
r? `@ghost`
`@rustbot` modify labels: rollup
Remove quotation from filename in stable_mir
Previously we had quotation marks in filenames which is obviously wrong this fixes that.
r? ```@celinval```
Fixed the `has_body()` function operator. Before that, this function was
returning false for all shims.
Change resolve_drop_in_place() to also return an instance for empty
shims, since they may still be required for vtable construction.
Add more APIs to retrieve information about types, and add more instance
resolution options.
Make `Instance::body()` return an Option<Body>, since not every instance
might have an available body. For example, foreign instances, virtual
instances, dependencies.
In cases like Kani, we will invoke the rustc_internal run command
directly for now. It would be handly to be able to have a callback
that can return a value.
We also need extra methods to convert stable constructs into internal
ones, so we can break down the transition into finer grain commits.
