Relax priv-in-pub lint on generic bounds and where clauses of trait impls.
The priv-in-pub lint is a legacy mechanism of the compiler, supplanted by a reachability-based [type privacy](https://github.com/rust-lang/rfcs/blob/master/text/2145-type-privacy.md) analysis. This PR does **not** relax type privacy; it only relaxes the lint (as proposed by the type privacy RFC) in the case of trait impls.
## Current Behavior
On public trait impls, it's currently an **error** to have a `where` bound constraining a private type with a trait:
```rust
pub trait Trait {}
pub struct Type {}
struct Priv {}
impl Trait for Priv {}
impl Trait for Type
where
Priv: Trait // ERROR
{}
```
...and it's a **warning** to have have a public type constrained by a private trait:
```rust
pub trait Trait {}
pub struct Type {}
pub struct Pub {}
trait Priv {}
impl Priv for Pub {}
impl Trait for Type
where
Pub: Priv // WARNING
{}
```
This lint applies to `where` clauses in other contexts, too; e.g. on free functions:
```rust
struct Priv<T>(T);
pub trait Pub {}
impl<T: Pub> Pub for Priv<T> {}
pub fn function<T>()
where
Priv<T>: Pub // WARNING
{}
```
**These constraints could be relaxed without issue.**
## New Behavior
This lint is relaxed for `where` clauses on trait impls, such that it's okay to have a `where` bound constraining a private type with a trait:
```rust
pub trait Trait {}
pub struct Type {}
struct Priv {}
impl Trait for Priv {}
impl Trait for Type
where
Priv: Trait // OK
{}
```
...and it's okay to have a public type constrained by a private trait:
```rust
pub trait Trait {}
pub struct Type {}
pub struct Pub {}
trait Priv {}
impl Priv for Pub {}
impl Trait for Type
where
Pub: Priv // OK
{}
```
## Rationale
While the priv-in-pub lint is not essential for soundness, it *can* help programmers avoid pitfalls that would make their libraries difficult to use by others. For instance, such a lint *is* useful for free functions; e.g. if a downstream crate tries to call the `function` in the previous snippet in a generic context:
```rust
fn callsite<T>()
where
Priv<T>: Pub // ERROR: omitting this bound is a compile error, but including it is too
{
function::<T>()
}
```
...it cannot do so without repeating `function`'s `where` bound, which we cannot do because `Priv` is out-of-scope. A lint for this case is arguably helpful.
However, this same reasoning **doesn't** hold for trait impls. To call an unconstrained method on a public trait impl with private bounds, you don't need to forward those private bounds, you can forward the public trait:
```rust
mod upstream {
pub trait Trait {
fn method(&self) {}
}
pub struct Type<T>(T);
pub struct Pub<T>(T);
trait Priv {}
impl<T: Priv> Priv for Pub<T> {}
impl<T> Trait for Type<T>
where
Pub<T>: Priv // WARNING
{}
}
mod downstream {
use super::upstream::*;
fn function<T>(value: Type<T>)
where
Type<T>: Trait // <- no private deets!
{
value.method();
}
}
```
**This PR only eliminates the lint on trait impls.** It leaves it intact for all other contexts, including trait definitions, inherent impls, and function definitions. It doesn't need to exist in those cases either, but I figured I'd first target a case where it's mostly pointless.
## Other Notes
- See discussion [on zulip](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/relax.20priv-in-pub.20lint.20for.20trait.20impl.20.60where.60.20bounds/near/222458397).
- This PR effectively reverts #79291.
rustc_metadata: Merge `get_ctor_def_id` and `get_ctor_kind`
Also avoid decoding the whole `ty::AssocItem` to get a `has_self` flag.
A small optimization and cleanup extracted from https://github.com/rust-lang/rust/pull/89059.
CTFE eval_fn_call: use FnAbi to determine argument skipping and compatibility
This makes use of the `FnAbi` type in CTFE/Miri, which `@eddyb` has been saying for years is what we should do.^^ `FnAbi` is used to
- determine which arguments to skip (rather than the previous heuristic of skipping ZST arguments with the Rust ABI)
- impose further restrictions on whether caller and callee are consistent in how a given argument is passed
I was hoping it would also simplify the code, but that is not the case -- the previous type compatibility checks are still required (AFAIK), only the ZST skipping is gone and that took barely any code. We also need some hacks because `FnAbi` assumes a certain way of implementing `caller_location` (by passing extra arguments), but Miri can just read the caller location from the call stack so it doesn't need those arguments. (The fact that every backend has to separately implement support for these arguments seems suboptimal -- looks like this might have been better implemented on the MIR level.) To avoid having to implement those unnecessary arguments in Miri, we just compute *whether* the argument is present on the caller/callee side, but don't actually pass that argument around.
I have no idea if this looks the way `@eddyb` thinks it should look... but it makes Miri's test suite pass. ;)
One of rustc's tests fails unfortunately (`ui/const-generics/issues/issue-67739.rs`), some const generic code that is evaluated too early -- I think that should raise `TooGeneric` but instead it ICEs. My assumption is this is some FnAbi code that has not been properly tested on polymorphic code, but it might also be me calling that FnAbi code the wrong way.
r? `@oli-obk` `@eddyb`
Fixes https://github.com/rust-lang/rust/issues/56166
Miri PR at https://github.com/rust-lang/miri/pull/1928
Remove useless `#[global_allocator]` from rustc and rustdoc.
This was added in #83152, which has several errors in its comments.
This commit also fix up the comments, which are quite wrong and
misleading.
r? `@alexcrichton`
Store a `DefId` instead of an `AdtDef` in `AggregateKind::Adt`
The `AggregateKind` enum ends up in the final mir `Body`. Currently,
any changes to `AdtDef` (regardless of how significant they are)
will legitimately cause the overall result of `optimized_mir` to change,
invalidating any codegen re-use involving that mir.
This will get worse once we start hashing the `Span` inside `FieldDef`
(which is itself contained in `AdtDef`).
To try to reduce these kinds of invalidations, this commit changes
`AggregateKind::Adt` to store just the `DefId`, instead of the full
`AdtDef`. This allows the result of `optimized_mir` to be unchanged
if the `AdtDef` changes in a way that doesn't actually affect any
of the MIR we build.
Update chalk to 0.75.0
- Compute flags in `intern_ty`
- Remove `tracing-serde` from `PERMITTED_DEPENDENCIES`
- Bump `tracing-tree` to 0.2.0
- Bump `tracing-subscriber` to 0.3.3
Fix duplicate derive clone suggestion
closes https://github.com/rust-lang/rust/issues/91492
The addition of:
```rust
derives.sort();
derives.dedup();
```
is what actually solves the problem.
The rest is just cleanup.
I want to improve the diagnostic message to provide the suggestion as a proper diff but ran into some problems, so I'll attempt that again in a follow up PR.
The `AggregateKind` enum ends up in the final mir `Body`. Currently,
any changes to `AdtDef` (regardless of how significant they are)
will legitimately cause the overall result of `optimized_mir` to change,
invalidating any codegen re-use involving that mir.
This will get worse once we start hashing the `Span` inside `FieldDef`
(which is itself contained in `AdtDef`).
To try to reduce these kinds of invalidations, this commit changes
`AggregateKind::Adt` to store just the `DefId`, instead of the full
`AdtDef`. This allows the result of `optimized_mir` to be unchanged
if the `AdtDef` changes in a way that doesn't actually affect any
of the MIR we build.
Sync rustc_codegen_cranelift
The main highlight this sync is improved support for inline assembly. Thanks `@nbdd0121!` Inline assembly is still disabled by default for builds in the main rust repo though. Cranelift will now also be built from the crates.io releases rather than the git repo. Git repos are incompatible with vendoring.
r? `@ghost`
`@rustbot` label +A-codegen +A-cranelift +T-compiler
Implement StableHash for BitSet and BitMatrix via Hash
This fixes an issue where bit sets / bit matrices the same word
content but a different domain size would receive the same hash.
Remove 'speculative evaluation' of predicates
Performing 'speculative evaluation' introduces caching bugs that
cannot be fixed without invasive changes to projection.
Hopefully, we can win back most of the performance lost by
re-adding 'cache completion'
Fixes#90662
This makes `Obligation` two words bigger, but avoids allocating a lot of
the time.
I previously tried this in #73983 and it didn't help much, but local
timings look more promising now.
Explicitly set no ELF flags for .rustc section
For a data section, the object crate will set the SHF_ALLOC by default, which is exactly what we don't want. Explicitly set sh_flags to zero to avoid this.
I checked with `objdump -h` that this produces the right flags for ELF.
Fixes#92013.
