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Don't call type_of on TAIT in defining scope in new solver

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This commit is contained in:
Michael Goulet 2023-06-28 17:41:04 +00:00
parent 87c8c83ec7
commit 388c230cf7
6 changed files with 67 additions and 101 deletions
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2
compiler/rustc_trait_selection/src/solve/eval_ctxt.rs
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@ -837,7 +837,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
}
}
pub(super) fn can_define_opaque_ty(&mut self, def_id: LocalDefId) -> bool {
pub(super) fn can_define_opaque_ty(&self, def_id: LocalDefId) -> bool {
self.infcx.opaque_type_origin(def_id).is_some()
}

27
compiler/rustc_trait_selection/src/solve/trait_goals.rs
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@ -7,6 +7,7 @@ use rustc_hir::{LangItem, Movability};
use rustc_infer::traits::query::NoSolution;
use rustc_infer::traits::util::supertraits;
use rustc_middle::traits::solve::{CanonicalResponse, Certainty, Goal, QueryResult};
use rustc_middle::traits::Reveal;
use rustc_middle::ty::fast_reject::{DeepRejectCtxt, TreatParams, TreatProjections};
use rustc_middle::ty::{self, ToPredicate, Ty, TyCtxt};
use rustc_middle::ty::{TraitPredicate, TypeVisitableExt};
@ -118,6 +119,32 @@ impl<'tcx> assembly::GoalKind<'tcx> for TraitPredicate<'tcx> {
return result;
}
// Don't call `type_of` on a local TAIT that's in the defining scope,
// since that may require calling `typeck` on the same item we're
// currently type checking, which will result in a fatal cycle that
// ideally we want to avoid, since we can make progress on this goal
// via an alias bound or a locally-inferred hidden type instead.
//
// Also, don't call `type_of` on a TAIT in `Reveal::All` mode, since
// we already normalize the self type in
// `assemble_candidates_after_normalizing_self_ty`, and we'd
// just be registering an identical candidate here.
//
// Returning `Err(NoSolution)` here is ok in `SolverMode::Coherence`
// since we'll always be registering an ambiguous candidate in
// `assemble_candidates_after_normalizing_self_ty` due to normalizing
// the TAIT.
if let ty::Alias(ty::Opaque, opaque_ty) = goal.predicate.self_ty().kind() {
if matches!(goal.param_env.reveal(), Reveal::All)
|| opaque_ty
.def_id
.as_local()
.is_some_and(|def_id| ecx.can_define_opaque_ty(def_id))
{
return Err(NoSolution);
}
}
ecx.probe_and_evaluate_goal_for_constituent_tys(
goal,
structural_traits::instantiate_constituent_tys_for_auto_trait,

2
tests/ui/traits/new-solver/dont-remap-tait-substs.rs
View File

@ -1,5 +1,5 @@
// compile-flags: -Ztrait-solver=next
// known-bug: #112825
// check-pass
// Makes sure we don't prepopulate the MIR typeck of `define`
// with `Foo<T, U> = T`, but instead, `Foo<B, A> = B`, so that

99
tests/ui/traits/new-solver/dont-remap-tait-substs.stderr
View File

@ -1,99 +0,0 @@
error[E0391]: cycle detected when computing type of `Foo::{opaque#0}`
--> $DIR/dont-remap-tait-substs.rs:10:24
|
LL | type Foo<T: Send, U> = impl NeedsSend<T>;
| ^^^^^^^^^^^^^^^^^
|
note: ...which requires borrow-checking `define`...
--> $DIR/dont-remap-tait-substs.rs:15:1
|
LL | fn define<A, B: Send>(a: A, b: B) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which again requires computing type of `Foo::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/dont-remap-tait-substs.rs:8:1
|
LL | / #![feature(type_alias_impl_trait)]
LL | |
LL | | type Foo<T: Send, U> = impl NeedsSend<T>;
LL | |
... |
LL | |
LL | | fn main() {}
| |____________^
error[E0391]: cycle detected when computing type of `Foo::{opaque#0}`
--> $DIR/dont-remap-tait-substs.rs:10:24
|
LL | type Foo<T: Send, U> = impl NeedsSend<T>;
| ^^^^^^^^^^^^^^^^^
|
note: ...which requires borrow-checking `define`...
--> $DIR/dont-remap-tait-substs.rs:15:1
|
LL | fn define<A, B: Send>(a: A, b: B) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which again requires computing type of `Foo::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/dont-remap-tait-substs.rs:8:1
|
LL | / #![feature(type_alias_impl_trait)]
LL | |
LL | | type Foo<T: Send, U> = impl NeedsSend<T>;
LL | |
... |
LL | |
LL | | fn main() {}
| |____________^
error[E0391]: cycle detected when computing type of `Foo::{opaque#0}`
--> $DIR/dont-remap-tait-substs.rs:10:24
|
LL | type Foo<T: Send, U> = impl NeedsSend<T>;
| ^^^^^^^^^^^^^^^^^
|
note: ...which requires borrow-checking `define`...
--> $DIR/dont-remap-tait-substs.rs:15:1
|
LL | fn define<A, B: Send>(a: A, b: B) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which again requires computing type of `Foo::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/dont-remap-tait-substs.rs:8:1
|
LL | / #![feature(type_alias_impl_trait)]
LL | |
LL | | type Foo<T: Send, U> = impl NeedsSend<T>;
LL | |
... |
LL | |
LL | | fn main() {}
| |____________^
error[E0391]: cycle detected when computing type of `Foo::{opaque#0}`
--> $DIR/dont-remap-tait-substs.rs:10:24
|
LL | type Foo<T: Send, U> = impl NeedsSend<T>;
| ^^^^^^^^^^^^^^^^^
|
note: ...which requires borrow-checking `define`...
--> $DIR/dont-remap-tait-substs.rs:15:1
|
LL | fn define<A, B: Send>(a: A, b: B) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
= note: ...which again requires computing type of `Foo::{opaque#0}`, completing the cycle
note: cycle used when checking item types in top-level module
--> $DIR/dont-remap-tait-substs.rs:8:1
|
LL | / #![feature(type_alias_impl_trait)]
LL | |
LL | | type Foo<T: Send, U> = impl NeedsSend<T>;
LL | |
... |
LL | |
LL | | fn main() {}
| |____________^
error: aborting due to 4 previous errors
For more information about this error, try `rustc --explain E0391`.

16
tests/ui/traits/new-solver/dont-type_of-tait-in-defining-scope.not_send.stderr Normal file
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@ -0,0 +1,16 @@
error[E0283]: type annotations needed: cannot satisfy `Foo: Send`
--> $DIR/dont-type_of-tait-in-defining-scope.rs:16:5
|
LL | needs_send::<Foo>();
| ^^^^^^^^^^^^^^^^^
|
= note: cannot satisfy `Foo: Send`
note: required by a bound in `needs_send`
--> $DIR/dont-type_of-tait-in-defining-scope.rs:13:18
|
LL | fn needs_send<T: Send>() {}
| ^^^^ required by this bound in `needs_send`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0283`.

22
tests/ui/traits/new-solver/dont-type_of-tait-in-defining-scope.rs Normal file
View File

@ -0,0 +1,22 @@
// revisions: is_send not_send
// compile-flags: -Ztrait-solver=next
//[is_send] check-pass
#![feature(type_alias_impl_trait)]
#[cfg(is_send)]
type Foo = impl Send;
#[cfg(not_send)]
type Foo = impl Sized;
fn needs_send<T: Send>() {}
fn test() {
needs_send::<Foo>();
//[not_send]~^ ERROR type annotations needed: cannot satisfy `Foo: Send`
}
fn main() {
let _: Foo = ();
}