Ensure that we never try to monomorphize the upcasting or vtable calls of impossible dyn types
Check for impossible obligations in the `dyn Trait` type we're trying to compute its the vtable upcasting and method call slots.
r? lcnr
Remove unnecessary layout assertions for object-safe receivers
The soundness of `DispatchFromDyn` relies on the fact that, like all other built-in marker-like layout traits (e.g. `Sized`, `CoerceUnsized`), the guarantees that they enforce in *generic* code via traits will result in assumptions that we can rely on in codegen.
Specifically, `DispatchFromDyn` ensures that we end up with a receiver that is a valid pointer type, and its implementation validity recursively ensures that the ABI of that pointer type upholds the `Scalar` or `ScalarPair` representation for sized and unsized pointees, respectively.
The check that this layout guarantee holds for arbitrary, possibly generic receiver types that also may exist in possibly impossible-to-instantiate where clauses is overkill IMO, and leads to several ICEs due to the fact that computing layouts before monomorphization is going to be fallible at best.
This PR removes the check altogether, since it just exists as a sanity check from very long ago, 6f2a161b1b.
Fixes#125810Fixes#90110
This PR is an alternative to #136195. cc `@adetaylor.` I didn't realize in that PR that the layout checks that were being modified were simply *sanity checks*, rather than being actually necessary for soundness.
Shorten error message for callable with wrong return type
```
error: expected `{closure@...}` to return `Ret`, but it returns `Other`
```
instead of
```
error: expected `{closure@...}` to be a closure that returns `Ret`, but it returns `Other`
```
Highlight clarifying information in "expected/found" error
When the expected and found types have the same textual representation, we add clarifying in parentheses. We now visually highlight it in the output.
Detect a corner case where the clarifying information would be the same for both types and skip it, as it doesn't add anything useful.
Tweak fn pointer suggestion span
Use a more targeted span when suggesting casting an `fn` item to an `fn` pointer.
```
error[E0308]: cannot coerce functions which must be inlined to function pointers
--> $DIR/cast.rs:10:33
|
LL | let _: fn(isize) -> usize = callee;
| ------------------ ^^^^^^ cannot coerce functions which must be inlined to function pointers
| |
| expected due to this
|
= note: expected fn pointer `fn(_) -> _`
found fn item `fn(_) -> _ {callee}`
= note: fn items are distinct from fn pointers
help: consider casting to a fn pointer
|
LL | let _: fn(isize) -> usize = callee as fn(isize) -> usize;
| +++++++++++++++++++++
```
```
error[E0308]: mismatched types
--> $DIR/fn-pointer-mismatch.rs:42:30
|
LL | let d: &fn(u32) -> u32 = foo;
| --------------- ^^^ expected `&fn(u32) -> u32`, found fn item
| |
| expected due to this
|
= note: expected reference `&fn(_) -> _`
found fn item `fn(_) -> _ {foo}`
help: consider using a reference
|
LL | let d: &fn(u32) -> u32 = &foo;
| +
```
Previously we'd point at the whole expression for replacement, instead of marking what was being added.
We could also modify the suggestions for `&(name as fn())`, but for that we require storing more accurate spans than we have now.
Rework "long type names" printing logic
Make it so more type-system types can be printed in a shortened version (like `Predicate`s).
Centralize printing the information about the "full type name path".
Make the "long type path" for the file where long types are written part of `Diag`, so that it becomes easier to keep track of it, and ensure it will always will be printed out last in the diagnostic by making its addition to the output implicit.
Tweak the shortening of types in "expected/found" labels.
Remove dead file `note.rs`.
Rename `tcx.ensure()` to `tcx.ensure_ok()`, and improve the associated docs
This is all based on my archaeology for https://rust-lang.zulipchat.com/#narrow/channel/182449-t-compiler.2Fhelp/topic/.60TyCtxtEnsure.60.
The main renamings are:
- `tcx.ensure()` → `tcx.ensure_ok()`
- `tcx.ensure_with_value()` → `tcx.ensure_done()`
- Query modifier `ensure_forwards_result_if_red` → `return_result_from_ensure_ok`
Hopefully these new names are a better fit for the *actual* function and purpose of these query call modes.
When the expected and found types have the same textual representation, we add clarifying in parentheses. We now visually highlight it in the output.
Detect a corner case where the clarifying information would be the same for both types and skip it, as it doesn't add anything useful.
```
error: expected `{closure@...}` to return `Ret`, but it returns `Other`
```
instead of
```
error: expected `{closure@...}` to be a closure that returns `Ret`, but it returns `Other`
```
Use a more targeted span when suggesting casting an `fn` item to an `fn` pointer.
```
error[E0308]: cannot coerce functions which must be inlined to function pointers
--> $DIR/cast.rs:10:33
|
LL | let _: fn(isize) -> usize = callee;
| ------------------ ^^^^^^ cannot coerce functions which must be inlined to function pointers
| |
| expected due to this
|
= note: expected fn pointer `fn(_) -> _`
found fn item `fn(_) -> _ {callee}`
= note: fn items are distinct from fn pointers
help: consider casting to a fn pointer
|
LL | let _: fn(isize) -> usize = callee as fn(isize) -> usize;
| +++++++++++++++++++++
```
```
error[E0308]: mismatched types
--> $DIR/fn-pointer-mismatch.rs:42:30
|
LL | let d: &fn(u32) -> u32 = foo;
| --------------- ^^^ expected `&fn(u32) -> u32`, found fn item
| |
| expected due to this
|
= note: expected reference `&fn(_) -> _`
found fn item `fn(_) -> _ {foo}`
help: consider using a reference
|
LL | let d: &fn(u32) -> u32 = &foo;
| +
```
Previously we'd point at the whole expression for replacement, instead of marking what was being added.
We could also modify the suggestions for `&(name as fn())`, but for that we require storing more accurate spans than we have now.
Implement MIR lowering for unsafe binders
This is the final bit of the unsafe binders puzzle. It implements MIR, CTFE, and codegen for unsafe binders, and enforces that (for now) they are `Copy`. Later on, I'll introduce a new trait that relaxes this requirement to being "is `Copy` or `ManuallyDrop<T>`" which more closely models how we treat union fields.
Namely, wrapping unsafe binders is now `Rvalue::WrapUnsafeBinder`, which acts much like an `Rvalue::Aggregate`. Unwrapping unsafe binders are implemented as a MIR projection `ProjectionElem::UnwrapUnsafeBinder`, which acts much like `ProjectionElem::Field`.
Tracking:
- https://github.com/rust-lang/rust/issues/130516
Manually walk into WF obligations in `BestObligation` proof tree visitor
When we encounter a `WellFormed` obligation in the `BestObligation` proof tree visitor, ignore the proof tree and call `wf::unnormalized_obligations` to derive well-formed obligations with the correct cause codes. This is to avoid having to replicate the somewhat delicate logic that `wf.rs` does to set up its obligation causes... Don't see a better way to do this.
vibes?? r? lcnr
Make it so more type-system types can be printed in a shortened version (like `Predicate`s).
Centralize printing the information about the "full type name path".
Make the "long type path" for the file where long types are written part of `Diag`, so that it becomes easier to keep track of it, and ensure it will always will be printed out last in the diagnostic by making its addition to the output implicit.
Tweak the shortening of types in "expected/found" labels.
Remove dead file `note.rs`.
Compiler: Finalize dyn compatibility renaming
Update the Reference link to use the new URL fragment from https://github.com/rust-lang/reference/pull/1666 (this change has finally hit stable). Fixes a FIXME.
Follow-up to #130826.
Part of #130852.
~~Blocking it on #133372.~~ (merged)
r? ghost
When encountering unexpected closure return type, point at return type/expression
```
error[E0271]: expected `{closure@fallback-closure-wrap.rs:18:40}` to be a closure that returns `()`, but it returns `!`
--> $DIR/fallback-closure-wrap.rs:19:9
|
LL | let error = Closure::wrap(Box::new(move || {
| -------
LL | panic!("Can't connect to server.");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `!`
|
= note: expected unit type `()`
found type `!`
= note: required for the cast from `Box<{closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47}>` to `Box<dyn FnMut()>`
```
```
error[E0271]: expected `{closure@dont-ice-for-type-mismatch-in-closure-in-async.rs:6:10}` to be a closure that returns `bool`, but it returns `Option<()>`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:16
|
LL | call(|| -> Option<()> {
| ---- ------^^^^^^^^^^
| | |
| | expected `bool`, found `Option<()>`
| required by a bound introduced by this call
|
= note: expected type `bool`
found enum `Option<()>`
note: required by a bound in `call`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:3:25
|
LL | fn call(_: impl Fn() -> bool) {}
| ^^^^ required by this bound in `call`
```
```
error[E0271]: expected `{closure@f670.rs:28:13}` to be a closure that returns `Result<(), _>`, but it returns `!`
--> f670.rs:28:20
|
28 | let c = |e| -> ! {
| -------^
| |
| expected `Result<(), _>`, found `!`
...
32 | f().or_else(c);
| ------- required by a bound introduced by this call
-Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs:1433:28
|
= note: expected enum `Result<(), _>`
found type `!`
note: required by a bound in `Result::<T, E>::or_else`
--> /home/gh-estebank/rust/library/core/src/result.rs:1406:39
|
1406 | pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
| ^^^^^^^^^^^^ required by this bound in `Result::<T, E>::or_else`
```
CC #111539.
Fix deduplication mismatches in vtables leading to upcasting unsoundness
We currently have two cases where subtleties in supertraits can trigger disagreements in the vtable layout, e.g. leading to a different vtable layout being accessed at a callsite compared to what was prepared during unsizing. Namely:
### #135315
In this example, we were not normalizing supertraits when preparing vtables. In the example,
```
trait Supertrait<T> {
fn _print_numbers(&self, mem: &[usize; 100]) {
println!("{mem:?}");
}
}
impl<T> Supertrait<T> for () {}
trait Identity {
type Selff;
}
impl<Selff> Identity for Selff {
type Selff = Selff;
}
trait Middle<T>: Supertrait<()> + Supertrait<T> {
fn say_hello(&self, _: &usize) {
println!("Hello!");
}
}
impl<T> Middle<T> for () {}
trait Trait: Middle<<() as Identity>::Selff> {}
impl Trait for () {}
fn main() {
(&() as &dyn Trait as &dyn Middle<()>).say_hello(&0);
}
```
When we prepare `dyn Trait`, we see a supertrait of `Middle<<() as Identity>::Selff>`, which itself has two supertraits `Supertrait<()>` and `Supertrait<<() as Identity>::Selff>`. These two supertraits are identical, but they are not duplicated because we were using structural equality and *not* considering normalization. This leads to a vtable layout with two trait pointers.
When we upcast to `dyn Middle<()>`, those two supertraits are now the same, leading to a vtable layout with only one trait pointer. This leads to an offset error, and we call the wrong method.
### #135316
This one is a bit more interesting, and is the bulk of the changes in this PR. It's a bit similar, except it uses binder equality instead of normalization to make the compiler get confused about two vtable layouts. In the example,
```
trait Supertrait<T> {
fn _print_numbers(&self, mem: &[usize; 100]) {
println!("{mem:?}");
}
}
impl<T> Supertrait<T> for () {}
trait Trait<T, U>: Supertrait<T> + Supertrait<U> {
fn say_hello(&self, _: &usize) {
println!("Hello!");
}
}
impl<T, U> Trait<T, U> for () {}
fn main() {
(&() as &'static dyn for<'a> Trait<&'static (), &'a ()>
as &'static dyn Trait<&'static (), &'static ()>)
.say_hello(&0);
}
```
When we prepare the vtable for `dyn for<'a> Trait<&'static (), &'a ()>`, we currently consider the PolyTraitRef of the vtable as the key for a supertrait. This leads two two supertraits -- `Supertrait<&'static ()>` and `for<'a> Supertrait<&'a ()>`.
However, we can upcast[^up] without offsetting the vtable from `dyn for<'a> Trait<&'static (), &'a ()>` to `dyn Trait<&'static (), &'static ()>`. This is just instantiating the principal trait ref for a specific `'a = 'static`. However, when considering those supertraits, we now have only one distinct supertrait -- `Supertrait<&'static ()>` (which is deduplicated since there are two supertraits with the same substitutions). This leads to similar offsetting issues, leading to the wrong method being called.
[^up]: I say upcast but this is a cast that is allowed on stable, since it's not changing the vtable at all, just instantiating the binder of the principal trait ref for some lifetime.
The solution here is to recognize that a vtable isn't really meaningfully higher ranked, and to just treat a vtable as corresponding to a `TraitRef` so we can do this deduplication more faithfully. That is to say, the vtable for `dyn for<'a> Tr<'a>` and `dyn Tr<'x>` are always identical, since they both would correspond to a set of free regions on an impl... Do note that `Tr<for<'a> fn(&'a ())>` and `Tr<fn(&'static ())>` are still distinct.
----
There's a bit more that can be cleaned up. In codegen, we can stop using `PolyExistentialTraitRef` basically everywhere. We can also fix SMIR to stop storing `PolyExistentialTraitRef` in its vtable allocations.
As for testing, it's difficult to actually turn this into something that can be tested with `rustc_dump_vtable`, since having multiple supertraits that are identical is a recipe for ambiguity errors. Maybe someone else is more creative with getting that attr to work, since the tests I added being run-pass tests is a bit unsatisfying. Miri also doesn't help here, since it doesn't really generate vtables that are offset by an index in the same way as codegen.
r? `@lcnr` for the vibe check? Or reassign, idk. Maybe let's talk about whether this makes sense.
<sup>(I guess an alternative would also be to not do any deduplication of vtable supertraits (or only a really conservative subset) rather than trying to normalize and deduplicate more faithfully here. Not sure if that works and is sufficient tho.)</sup>
cc `@steffahn` -- ty for the minimizations
cc `@WaffleLapkin` -- since you're overseeing the feature stabilization :3
Fixes#135315Fixes#135316
```
error[E0271]: expected `{closure@return-type-doesnt-match-bound.rs:18:13}` to be a closure that returns `Result<(), _>`, but it returns `!`
--> tests/ui/closures/return-type-doesnt-match-bound.rs:18:20
|
18 | let c = |e| -> ! { //~ ERROR to be a closure that returns
| -------^
| |
| expected `Result<(), _>`, found `!`
...
22 | f().or_else(c);
| ------- -
| |
| required by a bound introduced by this call
|
= note: expected enum `Result<(), _>`
found type `!`
note: required by a bound in `Result::<T, E>::or_else`
--> /home/gh-estebank/rust/library/core/src/result.rs:1406:39
|
1406 | pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
| ^^^^^^^^^^^^ required by this bound in `Result::<T, E>::or_else`
```
```
error[E0271]: expected `{closure@fallback-closure-wrap.rs:18:40}` to be a closure that returns `()`, but it returns `!`
--> $DIR/fallback-closure-wrap.rs:19:9
|
LL | let error = Closure::wrap(Box::new(move || {
| -------
LL | panic!("Can't connect to server.");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `!`
|
= note: expected unit type `()`
found type `!`
= note: required for the cast from `Box<{closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47}>` to `Box<dyn FnMut()>`
```
```
error[E0271]: expected `{closure@dont-ice-for-type-mismatch-in-closure-in-async.rs:6:10}` to be a closure that returns `bool`, but it returns `Option<()>`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:16
|
LL | call(|| -> Option<()> {
| ---- ------^^^^^^^^^^
| | |
| | expected `bool`, found `Option<()>`
| required by a bound introduced by this call
|
= note: expected type `bool`
found enum `Option<()>`
note: required by a bound in `call`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:3:25
|
LL | fn call(_: impl Fn() -> bool) {}
| ^^^^ required by this bound in `call`
```
```
error[E0271]: expected `{closure@f670.rs:28:13}` to be a closure that returns `Result<(), _>`, but it returns `!`
--> f670.rs:28:20
|
28 | let c = |e| -> ! {
| -------^
| |
| expected `Result<(), _>`, found `!`
...
32 | f().or_else(c);
| ------- required by a bound introduced by this call
-Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs:1433:28
|
= note: expected enum `Result<(), _>`
found type `!`
note: required by a bound in `Result::<T, E>::or_else`
--> /home/gh-estebank/rust/library/core/src/result.rs:1406:39
|
1406 | pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
| ^^^^^^^^^^^^ required by this bound in `Result::<T, E>::or_else`
```
Simplify and consolidate the way we handle construct `OutlivesEnvironment` for lexical region resolution
This is best reviewed commit-by-commit. I tried to consolidate the API for lexical region resolution *first*, then change the API when it was finally behind a single surface.
r? lcnr or reassign
Properly check that array length is valid type during built-in unsizing in index
This results in duplicated errors, but this class of errors is not new; in general, we aren't really equipped to detect cases where a WF error due to a field type would be shadowed by the parent struct of that field also not being WF.
This also adds a note for these types of mismatches to make it clear that this is due to an array type.
Fixes#134352
r? boxyuwu
Rollup of 7 pull requests
Successful merges:
- #135625 ([cfg_match] Document the use of expressions.)
- #135902 (Do not consider child bound assumptions for rigid alias)
- #135943 (Rename `Piece::String` to `Piece::Lit`)
- #136104 (Add mermaid graphs of NLL regions and SCCs to polonius MIR dump)
- #136143 (Update books)
- #136147 (ABI-required target features: warn when they are missing in base CPU)
- #136164 (Refactor FnKind variant to hold &Fn)
r? `@ghost`
`@rustbot` modify labels: rollup
Rename `Piece::String` to `Piece::Lit`
This renames Piece::String to Piece::Lit to avoid shadowing std::string::String and removes "pub use Piece::*;".
Do not consider child bound assumptions for rigid alias
r? lcnr
See first commit for the important details. For second commit, I also stacked a somewhat opinionated name change, though I can separate that if needed.
Fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/149
