Add `overflow_checks` intrinsic
This adds an intrinsic which allows code in a pre-built library to inherit the overflow checks option from a crate depending on it. This enables code in the standard library to explicitly change behavior based on whether `overflow_checks` are enabled, regardless of the setting used when standard library was compiled.
This is very similar to the `ub_checks` intrinsic, and refactors the two to use a common mechanism.
The primary use case for this is to allow the new `RangeFrom` iterator to yield the maximum element before overflowing, as requested [here](https://github.com/rust-lang/rust/issues/125687#issuecomment-2151118208). This PR includes a working `IterRangeFrom` implementation based on this new intrinsic that exhibits the desired behavior.
[Prior discussion on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/219381-t-libs/topic/Ability.20to.20select.20code.20based.20on.20.60overflow_checks.60.3F)
mgca: Add ConstArg representation for const items
tracking issue: rust-lang/rust#132980fixesrust-lang/rust#131046fixesrust-lang/rust#134641
As part of implementing `min_generic_const_args`, we need to distinguish const items that can be used in the type system, such as in associated const equality projections, from const items containing arbitrary const code, which must be kept out of the type system. Specifically, all "type consts" must be either concrete (no generics) or generic with a trivial expression like `N` or a path to another type const item.
To syntactically distinguish these cases, we require, for now at least, that users annotate all type consts with the `#[type_const]` attribute. Then, we validate that the const's right-hand side is indeed eligible to be a type const and represent it differently in the HIR.
We accomplish this representation using a new `ConstItemRhs` enum in the HIR, and a similar but simpler enum in the AST. When `#[type_const]` is **not** applied to a const (e.g. on stable), we represent const item right-hand sides (rhs's) as HIR bodies, like before. However, when the attribute is applied, we instead lower to a `hir::ConstArg`. This syntactically distinguishes between trivial const args (paths) and arbitrary expressions, which are represented using `AnonConst`s. Then in `generics_of`, we can take advantage of the existing machinery to bar the `AnonConst` rhs's from using parent generics.
Point at trait and associated item when that associated item is used in a const context. Suggest making the trait `#[const_trait]`.
```
error[E0015]: cannot call non-const method `<() as Trait>::foo` in constant functions
--> $DIR/inline-incorrect-early-bound-in-ctfe.rs:26:8
|
LL | ().foo();
| ^^^^^
|
note: method `foo` is not const because trait `Trait` is not const
--> $DIR/inline-incorrect-early-bound-in-ctfe.rs:13:1
|
LL | trait Trait {
| ^^^^^^^^^^^ this trait is not const
LL | fn foo(self);
| ------------- this method is not const
= note: calls in constant functions are limited to constant functions, tuple structs and tuple variants
help: consider making trait `Trait` const
|
LL + #[const_trait]
LL | trait Trait {
|
```
The `state: A::Domain` value is the primary things that's modified when
performing an analysis. The `Analysis` impl is immutable in every case
but one (`MaybeRequiredStorage`) and it now uses interior mutability.
As well as changing many `&mut A` arguments to `&A`, this also:
- lets `CowMut` be replaced with the simpler `SimpleCow` in `cursor.rs`;
- removes the need for the `RefCell` in `Formatter`;
- removes the need for `MaybeBorrowedLocals` to impl `Clone`, because
it's a unit type and it's now clear that its constructor can be used
directly instead of being put into a local variable and cloned.
Validate CopyForDeref and DerefTemps better and remove them from runtime MIR
(split from my WIP rust-lang/rust#145344)
This PR:
- Removes `Rvalue::CopyForDeref` and `LocalInfo::DerefTemp` from runtime MIR
- Using a new mir pass `EraseDerefTemps`
- `CopyForDeref(x)` is turned into `Use(Copy(x))`
- `DerefTemp` is turned into `Boring`
- Not sure if this part is actually necessary, it made more sense in rust-lang/rust#145344 with `DerefTemp` storing actual data that I wanted to keep from having to be kept in sync with the rest of the body in runtime MIR
- Checks in validation that `CopyForDeref` and `DerefTemp` are only used together
- Removes special handling for `CopyForDeref` from many places
- Removes `CopyForDeref` from `custom_mir` reverting rust-lang/rust#111587
- In runtime MIR simple copies can be used instead
- In post cleanup analysis MIR it was already wrong to use due to the lack of support for creating `DerefTemp` locals
- Possibly this should be its own PR?
- Adds an argument to `deref_finder` to avoid creating new `DerefTemp`s and `CopyForDeref` in runtime MIR.
- Ideally we would just avoid making intermediate derefs instead of fixing it at the end of a pass / during shim building
- Removes some usages of `deref_finder` that I found out don't actually do anything
r? oli-obk
Without any tests/benchmarks that show some improvement, it's hard to
know whether the change had any positive effect at all. (And if it did,
whether that effect is still achieved today.)
const checks for lifetime-extended temporaries: avoid 'top-level scope' terminology
This error recently got changed in https://github.com/rust-lang/rust/pull/140942 to use the terminology of "top-level scope", but after further discussion in https://github.com/rust-lang/reference/pull/1865 it seems the reference will not be using that terminology after all. So let's also remove it from the compiler again, and let's focus on what actually happens with these temporaries: their lifetime is extended until the end of the program.
r? ``@oli-obk`` ``@traviscross``
New const traits syntax
This PR only affects the AST and doesn't actually change anything semantically.
All occurrences of `~const` outside of libcore have been replaced by `[const]`. Within libcore we have to wait for rustfmt to be bumped in the bootstrap compiler. This will happen "automatically" (when rustfmt is run) during the bootstrap bump, as rustfmt converts `~const` into `[const]`. After this we can remove the `~const` support from the parser
Caveat discovered during impl: there is no legacy bare trait object recovery for `[const] Trait` as that snippet in type position goes down the slice /array parsing code and will error
r? ``@fee1-dead``
cc ``@nikomatsakis`` ``@traviscross`` ``@compiler-errors``
Implement parsing of pinned borrows
This PR implements part of #130494.
EDIT: It introduces `&pin mut $place` and `&pin const $place` as sugars for `std::pin::pin!($place)` and its shared reference equivalent, except that `$place` will not be moved when borrowing. The borrow check will be in charge of enforcing places cannot be moved or mutably borrowed since being pinned till dropped.
### Implementation steps:
- [x] parse the `&pin mut $place` and `&pin const $place` syntaxes
- [ ] borrowck of `&pin mut|const`
- [ ] support autoref of `&pin mut|const` when needed
This adds an `iter!` macro that can be used to create movable
generators.
This also adds a yield_expr feature so the `yield` keyword can be used
within iter! macro bodies. This was needed because several unstable
features each need `yield` expressions, so this allows us to stabilize
them separately from any individual feature.
Co-authored-by: Oli Scherer <github35764891676564198441@oli-obk.de>
Co-authored-by: Jieyou Xu <jieyouxu@outlook.com>
Co-authored-by: Travis Cross <tc@traviscross.com>
Continuing the work from #137350.
Removes the unused methods: `expect_variant`, `expect_field`,
`expect_foreign_item`.
Every method gains a `hir_` prefix.
Continuing the work started in #136466.
Every method gains a `hir_` prefix, though for the ones that already
have a `par_` or `try_par_` prefix I added the `hir_` after that.
The wording unsafe pointer is less common and not mentioned in a lot of
places, instead this is usually called a "raw pointer". For the sake of
uniformity, we rename this method.
This came up during the review of
https://github.com/rust-lang/rust/pull/134424.
