Remove unused/unnecessary features
~~The bulk of the actual code changes here is replacing try blocks with equivalent closures. I'm not entirely sure that's a good idea since it may have perf impact, happy to revert if that's the case/the change is unwanted.~~
I also removed a lot of `recursion_limit = "256"` since everything seems to build fine without that and most don't have any comment justifying it.
remove StructuralEq trait
The documentation given for the trait is outdated: *all* function pointers implement `PartialEq` and `Eq` these days. So the `StructuralEq` trait doesn't really seem to have any reason to exist any more.
One side-effect of this PR is that we allow matching on some consts that do not implement `Eq`. However, we already allowed matching on floats and consts containing floats, so this is not new, it is just allowed in more cases now. IMO it makes no sense at all to allow float matching but also sometimes require an `Eq` instance. If we want to require `Eq` we should adjust https://github.com/rust-lang/rust/pull/115893 to check for `Eq`, and rule out float matching for good.
Fixes https://github.com/rust-lang/rust/issues/115881
Replacement of #114390: Add new intrinsic `is_var_statically_known` and optimize pow for powers of two
This adds a new intrinsic `is_val_statically_known` that lowers to [``@llvm.is.constant.*`](https://llvm.org/docs/LangRef.html#llvm-is-constant-intrinsic).` It also applies the intrinsic in the int_pow methods to recognize and optimize the idiom `2isize.pow(x)`. See #114390 for more discussion.
While I have extended the scope of the power of two optimization from #114390, I haven't added any new uses for the intrinsic. That can be done in later pull requests.
Note: When testing or using the library, be sure to use `--stage 1` or higher. Otherwise, the intrinsic will be a noop and the doctests will be skipped. If you are trying out edits, you may be interested in [`--keep-stage 0`](https://rustc-dev-guide.rust-lang.org/building/suggested.html#faster-builds-with---keep-stage).
Fixes#47234Resolves#114390
`@Centri3`
Remove all ConstPropNonsense
We track all locals and projections on them ourselves within the const propagator and only use the InterpCx to actually do some low level operations or read from constants (via `OpTy` we get for said constants).
This helps moving the const prop lint out from the normal pipeline and running it just based on borrowck information. This in turn allows us to make progress on https://github.com/rust-lang/rust/pull/108730#issuecomment-1875557745
there are various follow up cleanups that can be done after this PR (e.g. not matching on Rvalue twice and doing binop checks twice), but lets try landing this one first.
r? `@RalfJung`
Return a finite number of AllocIds per ConstAllocation in Miri
Before this, every evaluation of a const slice would produce a new AllocId. So in Miri, this program used to have unbounded memory use:
```rust
fn main() {
loop {
helper();
}
}
fn helper() {
"ouch";
}
```
Every trip around the loop creates a new AllocId which we need to keep track of a base address for. And the provenance GC can never clean up that AllocId -> u64 mapping, because the AllocId is for a const allocation which will never be deallocated.
So this PR moves the logic of producing an AllocId for a ConstAllocation to the Machine trait, and the implementation that Miri provides will only produce 16 AllocIds for each allocation. The cache is also keyed on the Instance that the const is evaluated in, so that equal consts evaluated in two functions will have disjoint base addresses.
r? RalfJung
Do not normalize closure signature when building `FnOnce` shim
It is not necessary to normalize the closure signature when building an `FnOnce` shim for an `Fn`/`FnMut` closure. That closure shim is just calling `FnMut::call_mut(&mut self)` anyways.
It's also somewhat sketchy that we were ever doing this to begin with, since we're normalizing with a `ParamEnv::reveal_all()` param-env, which is definitely not right with possibly polymorphic substs.
This cuts out a tiny bit of unnecessary work in `Instance::resolve` and simplifies the signature because now we can unconditionally return an `Instance`.
const-eval interning: get rid of type-driven traversal
This entirely replaces our const-eval interner, i.e. the code that takes the final result of a constant evaluation from the local memory of the const-eval machine to the global `tcx` memory. The main goal of this change is to ensure that we can detect mutable references that sneak into this final value -- this is something we want to reject for `static` and `const`, and while const-checking performs some static analysis to ensure this, I would be much more comfortable stabilizing const_mut_refs if we had a dynamic check that sanitizes the final value. (This is generally the approach we have been using on const-eval: do a static check to give nice errors upfront, and then do a dynamic check to be really sure that the properties we need for soundness, actually hold.)
We can do this now that https://github.com/rust-lang/rust/pull/118324 landed and each pointer comes with a bit (completely independent of its type) storing whether mutation is permitted through this pointer or not.
The new interner is a lot simpler than the old one: previously we did a complete type-driven traversal to determine the mutability of all memory we see, and then a second pass to intern any leftover raw pointers. The new interner simply recursively traverses the allocation holding the final result, and all allocations reachable from it (which can be determined from the raw bytes of the result, without knowing anything about types), and ensures they all get interned. The initial allocation is interned as immutable for `const` and pomoted and non-interior-mutable `static`; all other allocations are interned as immutable for `static`, `const`, and promoted. The main subtlety is justifying that those inner allocations may indeed be interned immutably, i.e., that mutating them later would anyway already be UB:
- for promoteds, we rely on the analysis that does promotion to ensure that this is sound.
- for `const` and `static`, we check that all pointers in the final result that point to things that are new (i.e., part of this const evaluation) are immutable, i.e., were created via `&<expr>` at a non-interior-mutable type. Mutation through immutable pointers is UB so we are free to intern that memory as immutable.
Interning raises an error if it encounters a dangling pointer or a mutable pointer that violates the above rules.
I also extended our type-driven const validity checks to ensure that `&mut T` in the final value of a const points to mutable memory, at least if `T` is not zero-sized. This catches cases of people turning `&i32` into `&mut i32` (which would still be considered a read-only pointer). Similarly, when these checks encounter an `UnsafeCell`, they are checking that it lives in mutable memory. (Both of these only traverse the newly created values; if those point to other consts/promoteds, the check stops there. But that's okay, we don't have to catch all the UB.) I co-developed this with the stricter interner changes but I can split it out into a separate PR if you prefer.
This PR does have the immediate effect of allowing some new code on stable, for instance:
```rust
const CONST_RAW: *const Vec<i32> = &Vec::new() as *const _;
```
Previously that code got rejected since the type-based interner didn't know what to do with that pointer. It's a raw pointer, we cannot trust its type. The new interner does not care about types so it sees no issue with this code; there's an immutable pointer pointing to some read-only memory (storing a `Vec<i32>`), all is good. Accepting this code pretty much commits us to non-type-based interning, but I think that's the better strategy anyway.
This PR also leads to slightly worse error messages when the final value of a const contains a dangling reference. Previously we would complete interning and then the type-based validation would detect this dangling reference and show a nice error saying where in the value (i.e., in which field) the dangling reference is located. However, the new interner cannot distinguish dangling references from dangling raw pointers, so it must throw an error when it encounters either of them. It doesn't have an understanding of the value structure so all it can say is "somewhere in this constant there's a dangling pointer". (Later parts of the compiler don't like dangling pointers/references so we have to reject them either during interning or during validation.) This could potentially be improved by doing validation before interning, but that's a larger change that I have not attempted yet. (It's also subtle since we do want validation to use the final mutability bits of all involved allocations, and currently it is interning that marks a bunch of allocations as immutable -- that would have to still happen before validation.)
`@rust-lang/wg-const-eval` I hope you are okay with this plan. :)
`@rust-lang/lang` paging you in since this accepts new code on stable as explained above. Please let me know if you think FCP is necessary.
Fix overflow check
Make MIRI choose the path randomly and rename the intrinsic
Add back test
Add miri test and make it operate on `ptr`
Define `llvm.is.constant` for primitives
Update MIRI comment and fix test in stage2
Add const eval test
Clarify that both branches must have the same side effects
guaranteed non guarantee
use immediate type instead
Co-Authored-By: Ralf Jung <post@ralfj.de>
We have `span_delayed_bug` and often pass it a `DUMMY_SP`. This commit
adds `delayed_bug`, which matches pairs like `err`/`span_err` and
`warn`/`span_warn`.
Add helper for when we want to know if an item has a host param
r? ````@fmease```` since you're a good reviewer and no good deed goes unpunished
This helper will see far more usages as built-in traits get constified.
This works for most of its call sites. This is nice, because `emit` very
much makes sense as a consuming operation -- indeed,
`DiagnosticBuilderState` exists to ensure no diagnostic is emitted
twice, but it uses runtime checks.
For the small number of call sites where a consuming emit doesn't work,
the commit adds `DiagnosticBuilder::emit_without_consuming`. (This will
be removed in subsequent commits.)
Likewise, `emit_unless` becomes consuming. And `delay_as_bug` becomes
consuming, while `delay_as_bug_without_consuming` is added (which will
also be removed in subsequent commits.)
All this requires significant changes to `DiagnosticBuilder`'s chaining
methods. Currently `DiagnosticBuilder` method chaining uses a
non-consuming `&mut self -> &mut Self` style, which allows chaining to
be used when the chain ends in `emit()`, like so:
```
struct_err(msg).span(span).emit();
```
But it doesn't work when producing a `DiagnosticBuilder` value,
requiring this:
```
let mut err = self.struct_err(msg);
err.span(span);
err
```
This style of chaining won't work with consuming `emit` though. For
that, we need to use to a `self -> Self` style. That also would allow
`DiagnosticBuilder` production to be chained, e.g.:
```
self.struct_err(msg).span(span)
```
However, removing the `&mut self -> &mut Self` style would require that
individual modifications of a `DiagnosticBuilder` go from this:
```
err.span(span);
```
to this:
```
err = err.span(span);
```
There are *many* such places. I have a high tolerance for tedious
refactorings, but even I gave up after a long time trying to convert
them all.
Instead, this commit has it both ways: the existing `&mut self -> Self`
chaining methods are kept, and new `self -> Self` chaining methods are
added, all of which have a `_mv` suffix (short for "move"). Changes to
the existing `forward!` macro lets this happen with very little
additional boilerplate code. I chose to add the suffix to the new
chaining methods rather than the existing ones, because the number of
changes required is much smaller that way.
This doubled chainging is a bit clumsy, but I think it is worthwhile
because it allows a *lot* of good things to subsequently happen. In this
commit, there are many `mut` qualifiers removed in places where
diagnostics are emitted without being modified. In subsequent commits:
- chaining can be used more, making the code more concise;
- more use of chaining also permits the removal of redundant diagnostic
APIs like `struct_err_with_code`, which can be replaced easily with
`struct_err` + `code_mv`;
- `emit_without_diagnostic` can be removed, which simplifies a lot of
machinery, removing the need for `DiagnosticBuilderState`.
Migrate memory overlap check from validator to lint
The check attempts to identify potential undefined behaviour, rather
than whether MIR is well-formed. It belongs in the lint not validator.
Follow up to changes from #119077.
`Diagnostic` has 40 methods that return `&mut Self` and could be
considered setters. Four of them have a `set_` prefix. This doesn't seem
necessary for a type that implements the builder pattern. This commit
removes the `set_` prefixes on those four methods.
Make closures carry their own ClosureKind
Right now, we use the "`movability`" field of `hir::Closure` to distinguish a closure and a coroutine. This is paired together with the `CoroutineKind`, which is located not in the `hir::Closure`, but the `hir::Body`. This is strange and redundant.
This PR introduces `ClosureKind` with two variants -- `Closure` and `Coroutine`, which is put into `hir::Closure`. The `CoroutineKind` is thus removed from `hir::Body`, and `Option<Movability>` no longer needs to be a stand-in for "is this a closure or a coroutine".
r? eholk
Remove `DiagCtxt` API duplication
`DiagCtxt` defines the internal API for creating and emitting diagnostics: methods like `struct_err`, `struct_span_warn`, `note`, `create_fatal`, `emit_bug`. There are over 50 methods.
Some of these methods are then duplicated across several other types: `Session`, `ParseSess`, `Parser`, `ExtCtxt`, and `MirBorrowckCtxt`. `Session` duplicates the most, though half the ones it does are unused. Each duplicated method just calls forward to the corresponding method in `DiagCtxt`. So this duplication exists to (in the best case) shorten chains like `ecx.tcx.sess.parse_sess.dcx.emit_err()` to `ecx.emit_err()`.
This API duplication is ugly and has been bugging me for a while. And it's inconsistent: there's no real logic about which methods are duplicated, and the use of `#[rustc_lint_diagnostic]` and `#[track_caller]` attributes vary across the duplicates.
This PR removes the duplicated API methods and makes all diagnostic creation and emission go through `DiagCtxt`. It also adds `dcx` getter methods to several types to shorten chains. This approach scales *much* better than API duplication; indeed, the PR adds `dcx()` to numerous types that didn't have API duplication: `TyCtxt`, `LoweringCtxt`, `ConstCx`, `FnCtxt`, `TypeErrCtxt`, `InferCtxt`, `CrateLoader`, `CheckAttrVisitor`, and `Resolver`. These result in a lot of changes from `foo.tcx.sess.emit_err()` to `foo.dcx().emit_err()`. (You could do this with more types, but it gets into diminishing returns territory for types that don't emit many diagnostics.)
After all these changes, some call sites are more verbose, some are less verbose, and many are the same. The total number of lines is reduced, mostly because of the removed API duplication. And consistency is increased, because calls to `emit_err` and friends are always preceded with `.dcx()` or `.dcx`.
r? `@compiler-errors`
