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Strongly prefer alias and param-env bounds

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This commit is contained in:
Michael Goulet 2023-05-22 23:48:06 +00:00
parent a2d806d56d
commit 97c11ffb22
8 changed files with 78 additions and 32 deletions
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14
compiler/rustc_trait_selection/src/solve/assembly/mod.rs
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@ -2,7 +2,6 @@
use super::search_graph::OverflowHandler;
use super::{EvalCtxt, SolverMode};
use crate::solve::CanonicalResponseExt;
use crate::traits::coherence;
use rustc_data_structures::fx::FxIndexSet;
use rustc_hir::def_id::DefId;
@ -744,13 +743,18 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
SolverMode::Normal => {
let param_env_responses = candidates
.iter()
.filter(|c| matches!(c.source, CandidateSource::ParamEnv(_)))
.filter(|c| {
matches!(
c.source,
CandidateSource::ParamEnv(_) | CandidateSource::AliasBound
)
})
.map(|c| c.result)
.collect::<Vec<_>>();
if let Some(result) = self.try_merge_responses(&param_env_responses) {
if result.has_only_region_constraints() {
return Ok(result);
}
// We strongly prefer alias and param-env bounds here, even if they affect inference.
// See https://github.com/rust-lang/trait-system-refactor-initiative/issues/11.
return Ok(result);
}
}
}

2
tests/ui/dyn-star/param-env-infer.current.stderr
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@ -8,7 +8,7 @@ LL | #![feature(dyn_star, pointer_like_trait)]
= note: `#[warn(incomplete_features)]` on by default
error[E0282]: type annotations needed
--> $DIR/param-env-infer.rs:12:10
--> $DIR/param-env-infer.rs:13:10
|
LL | t as _
| ^ cannot infer type

65
tests/ui/dyn-star/param-env-infer.next.stderr
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@ -7,12 +7,67 @@ LL | #![feature(dyn_star, pointer_like_trait)]
= note: see issue #102425 <https://github.com/rust-lang/rust/issues/102425> for more information
= note: `#[warn(incomplete_features)]` on by default
error[E0282]: type annotations needed
--> $DIR/param-env-infer.rs:12:10
error[E0391]: cycle detected when computing type of `make_dyn_star::{opaque#0}`
--> $DIR/param-env-infer.rs:11:60
|
LL | t as _
| ^ cannot infer type
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
note: ...which requires borrow-checking `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires promoting constants in MIR for `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires preparing `make_dyn_star` for borrow checking...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires unsafety-checking `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building MIR for `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires match-checking `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires building THIR for `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: ...which requires type-checking `make_dyn_star`...
--> $DIR/param-env-infer.rs:11:1
|
LL | fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which requires computing layout of `make_dyn_star::{opaque#0}`...
= note: ...which requires normalizing `make_dyn_star::{opaque#0}`...
= note: ...which again requires computing type of `make_dyn_star::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/param-env-infer.rs:5:1
|
LL | / #![feature(dyn_star, pointer_like_trait)]
LL | |
LL | |
LL | | use std::fmt::Debug;
... |
LL | |
LL | | fn main() {}
| |____________^
error: aborting due to previous error; 1 warning emitted
For more information about this error, try `rustc --explain E0282`.
For more information about this error, try `rustc --explain E0391`.

3
tests/ui/dyn-star/param-env-infer.rs
View File

@ -9,8 +9,9 @@ use std::fmt::Debug;
use std::marker::PointerLike;
fn make_dyn_star<'a, T: PointerLike + Debug + 'a>(t: T) -> impl PointerLike + Debug + 'a {
//[next]~^ ERROR cycle detected when computing type of `make_dyn_star::{opaque#0}`
t as _
//~^ ERROR type annotations needed
//[current]~^ ERROR type annotations needed
}
fn main() {}

4
tests/ui/traits/new-solver/alias_eq_dont_use_normalizes_to_if_substs_eq.rs
View File

@ -1,5 +1,8 @@
// compile-flags: -Ztrait-solver=next
// check-pass
// (should not pass, should be turned into a coherence-only test)
// check that when computing `alias-eq(<() as Foo<u16, T>>::Assoc, <() as Foo<?0, T>>::Assoc)`
// we do not infer `?0 = u8` via the `for<STOP> (): Foo<u8, STOP>` impl or `?0 = u16` by
// relating substs as either could be a valid solution.
@ -36,7 +39,6 @@ where
{
// `<() as Foo<u16, STOP>>::Assoc == <() as Foo<_, STOP>>::Assoc`
let _: <() as Foo<u16, T>>::Assoc = output::<_, T>();
//~^ error: type annotations needed
// let _: <() as Foo<u16, T>>::Assoc = output::<u8, T>(); // OK
// let _: <() as Foo<u16, T>>::Assoc = output::<u16, T>(); // OK

9
tests/ui/traits/new-solver/alias_eq_dont_use_normalizes_to_if_substs_eq.stderr
View File

@ -1,9 +0,0 @@
error[E0282]: type annotations needed
--> $DIR/alias_eq_dont_use_normalizes_to_if_substs_eq.rs:38:41
|
LL | let _: <() as Foo<u16, T>>::Assoc = output::<_, T>();
| ^^^^^^^^^^^^^^ cannot infer type of the type parameter `T` declared on the function `output`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0282`.

4
tests/ui/traits/new-solver/alias_eq_substs_eq_not_intercrate.rs
View File

@ -1,5 +1,8 @@
// compile-flags: -Ztrait-solver=next
// check-pass
// (should not pass, should be turned into a coherence-only test)
// check that a `alias-eq(<?0 as TraitB>::Assoc, <T as TraitB>::Assoc)` goal fails.
// FIXME(deferred_projection_equality): add a test that this is true during coherence
@ -14,7 +17,6 @@ fn needs_a<T: TraitB>() -> T::Assoc {
fn bar<T: TraitB>() {
let _: <_ as TraitB>::Assoc = needs_a::<T>();
//~^ error: type annotations needed
}
fn main() {}

9
tests/ui/traits/new-solver/alias_eq_substs_eq_not_intercrate.stderr
View File

@ -1,9 +0,0 @@
error[E0282]: type annotations needed
--> $DIR/alias_eq_substs_eq_not_intercrate.rs:16:12
|
LL | let _: <_ as TraitB>::Assoc = needs_a::<T>();
| ^^^^^^^^^^^^^^^^^^^^ cannot infer type for associated type `<_ as TraitB>::Assoc`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0282`.