diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs index 8e9751f4529..c35524373c7 100644 --- a/compiler/rustc_middle/src/traits/select.rs +++ b/compiler/rustc_middle/src/traits/select.rs @@ -193,7 +193,6 @@ pub enum SelectionCandidate<'tcx> { /// The evaluation results are ordered: /// - `EvaluatedToOk` implies `EvaluatedToOkModuloRegions` /// implies `EvaluatedToAmbig` implies `EvaluatedToAmbigStackDependent` -/// - `EvaluatedToErr` implies `EvaluatedToErrStackDependent` /// - the "union" of evaluation results is equal to their maximum - /// all the "potential success" candidates can potentially succeed, /// so they are noops when unioned with a definite error, and within @@ -219,52 +218,9 @@ pub enum EvaluationResult { /// variables. We are somewhat imprecise there, so we don't actually /// know the real result. /// - /// This can't be trivially cached for the same reason as `EvaluatedToErrStackDependent`. + /// This can't be trivially cached because the result depends on the + /// stack results. EvaluatedToAmbigStackDependent, - /// Evaluation failed because we encountered an obligation we are already - /// trying to prove on this branch. - /// - /// We know this branch can't be a part of a minimal proof-tree for - /// the "root" of our cycle, because then we could cut out the recursion - /// and maintain a valid proof tree. However, this does not mean - /// that all the obligations on this branch do not hold -- it's possible - /// that we entered this branch "speculatively", and that there - /// might be some other way to prove this obligation that does not - /// go through this cycle -- so we can't cache this as a failure. - /// - /// For example, suppose we have this: - /// - /// ```rust,ignore (pseudo-Rust) - /// pub trait Trait { fn xyz(); } - /// // This impl is "useless", but we can still have - /// // an `impl Trait for SomeUnsizedType` somewhere. - /// impl Trait for T { fn xyz() {} } - /// - /// pub fn foo() { - /// ::xyz(); - /// } - /// ``` - /// - /// When checking `foo`, we have to prove `T: Trait`. This basically - /// translates into this: - /// - /// ```plain,ignore - /// (T: Trait + Sized →_\impl T: Trait), T: Trait ⊢ T: Trait - /// ``` - /// - /// When we try to prove it, we first go the first option, which - /// recurses. This shows us that the impl is "useless" -- it won't - /// tell us that `T: Trait` unless it already implemented `Trait` - /// by some other means. However, that does not prevent `T: Trait` - /// does not hold, because of the bound (which can indeed be satisfied - /// by `SomeUnsizedType` from another crate). - // - // FIXME: when an `EvaluatedToErrStackDependent` goes past its parent root, we - // ought to convert it to an `EvaluatedToErr`, because we know - // there definitely isn't a proof tree for that obligation. Not - // doing so is still sound -- there isn't any proof tree, so the - // branch still can't be a part of a minimal one -- but does not re-enable caching. - EvaluatedToErrStackDependent, /// Evaluation failed. EvaluatedToErr, } @@ -290,13 +246,13 @@ pub fn may_apply(self) -> bool { | EvaluatedToAmbig | EvaluatedToAmbigStackDependent => true, - EvaluatedToErr | EvaluatedToErrStackDependent => false, + EvaluatedToErr => false, } } pub fn is_stack_dependent(self) -> bool { match self { - EvaluatedToAmbigStackDependent | EvaluatedToErrStackDependent => true, + EvaluatedToAmbigStackDependent => true, EvaluatedToOkModuloOpaqueTypes | EvaluatedToOk diff --git a/compiler/rustc_trait_selection/src/infer.rs b/compiler/rustc_trait_selection/src/infer.rs index f694dd00703..7056288e758 100644 --- a/compiler/rustc_trait_selection/src/infer.rs +++ b/compiler/rustc_trait_selection/src/infer.rs @@ -49,8 +49,7 @@ fn type_is_sized_modulo_regions(&self, param_env: ty::ParamEnv<'tcx>, ty: Ty<'tc /// - the parameter environment /// /// Invokes `evaluate_obligation`, so in the event that evaluating - /// `Ty: Trait` causes overflow, EvaluatedToErrStackDependent - /// (or EvaluatedToAmbigStackDependent) will be returned. + /// `Ty: Trait` causes overflow, EvaluatedToAmbigStackDependent will be returned. #[instrument(level = "debug", skip(self, params), ret)] fn type_implements_trait( &self, diff --git a/compiler/rustc_trait_selection/src/traits/coherence.rs b/compiler/rustc_trait_selection/src/traits/coherence.rs index 2712ba19451..6e768b23ef8 100644 --- a/compiler/rustc_trait_selection/src/traits/coherence.rs +++ b/compiler/rustc_trait_selection/src/traits/coherence.rs @@ -210,7 +210,7 @@ fn overlap<'tcx>( .intercrate(true) .with_next_trait_solver(tcx.next_trait_solver_in_coherence()) .build(); - let selcx = &mut SelectionContext::with_treat_inductive_cycle_as_ambig(&infcx); + let selcx = &mut SelectionContext::new(&infcx); if track_ambiguity_causes.is_yes() { selcx.enable_tracking_intercrate_ambiguity_causes(); } diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs index 084f7b1a8c2..3fbe8e39d1e 100644 --- a/compiler/rustc_trait_selection/src/traits/select/mod.rs +++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs @@ -126,8 +126,6 @@ pub struct SelectionContext<'cx, 'tcx> { /// policy. In essence, canonicalized queries need their errors propagated /// rather than immediately reported because we do not have accurate spans. query_mode: TraitQueryMode, - - treat_inductive_cycle: TreatInductiveCycleAs, } // A stack that walks back up the stack frame. @@ -208,27 +206,6 @@ enum BuiltinImplConditions<'tcx> { Ambiguous, } -#[derive(Copy, Clone)] -pub enum TreatInductiveCycleAs { - /// This is the previous behavior, where `Recur` represents an inductive - /// cycle that is known not to hold. This is not forwards-compatible with - /// coinduction, and will be deprecated. This is the default behavior - /// of the old trait solver due to back-compat reasons. - Recur, - /// This is the behavior of the new trait solver, where inductive cycles - /// are treated as ambiguous and possibly holding. - Ambig, -} - -impl From for EvaluationResult { - fn from(treat: TreatInductiveCycleAs) -> EvaluationResult { - match treat { - TreatInductiveCycleAs::Ambig => EvaluatedToAmbigStackDependent, - TreatInductiveCycleAs::Recur => EvaluatedToErrStackDependent, - } - } -} - impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> { pub fn new(infcx: &'cx InferCtxt<'tcx>) -> SelectionContext<'cx, 'tcx> { SelectionContext { @@ -236,19 +213,6 @@ pub fn new(infcx: &'cx InferCtxt<'tcx>) -> SelectionContext<'cx, 'tcx> { freshener: infcx.freshener(), intercrate_ambiguity_causes: None, query_mode: TraitQueryMode::Standard, - treat_inductive_cycle: TreatInductiveCycleAs::Recur, - } - } - - pub fn with_treat_inductive_cycle_as_ambig( - infcx: &'cx InferCtxt<'tcx>, - ) -> SelectionContext<'cx, 'tcx> { - // Should be executed in a context where caching is disabled, - // otherwise the cache is poisoned with the temporary result. - assert!(infcx.intercrate); - SelectionContext { - treat_inductive_cycle: TreatInductiveCycleAs::Ambig, - ..SelectionContext::new(infcx) } } @@ -756,7 +720,7 @@ fn evaluate_predicate_recursively<'o>( stack.update_reached_depth(stack_arg.1); return Ok(EvaluatedToOk); } else { - return Ok(self.treat_inductive_cycle.into()); + return Ok(EvaluatedToAmbigStackDependent); } } return Ok(EvaluatedToOk); @@ -875,7 +839,7 @@ fn evaluate_predicate_recursively<'o>( } } ProjectAndUnifyResult::FailedNormalization => Ok(EvaluatedToAmbig), - ProjectAndUnifyResult::Recursive => Ok(self.treat_inductive_cycle.into()), + ProjectAndUnifyResult::Recursive => Ok(EvaluatedToAmbigStackDependent), ProjectAndUnifyResult::MismatchedProjectionTypes(_) => Ok(EvaluatedToErr), } } @@ -1180,7 +1144,7 @@ fn check_evaluation_cycle( Some(EvaluatedToOk) } else { debug!("evaluate_stack --> recursive, inductive"); - Some(self.treat_inductive_cycle.into()) + Some(EvaluatedToAmbigStackDependent) } } else { None diff --git a/tests/ui/marker_trait_attr/unsound-overlap.rs b/tests/ui/marker_trait_attr/unsound-overlap.rs index 2e5101b822c..2ce26b610f6 100644 --- a/tests/ui/marker_trait_attr/unsound-overlap.rs +++ b/tests/ui/marker_trait_attr/unsound-overlap.rs @@ -8,6 +8,7 @@ trait B {} impl B for T {} impl A for T {} impl A for &str {} +//~^ ERROR type annotations needed: cannot satisfy `&str: A` impl A for (T,) {} trait TraitWithAssoc { type Assoc; diff --git a/tests/ui/marker_trait_attr/unsound-overlap.stderr b/tests/ui/marker_trait_attr/unsound-overlap.stderr index 5e58f5227ed..13498fa4b22 100644 --- a/tests/ui/marker_trait_attr/unsound-overlap.stderr +++ b/tests/ui/marker_trait_attr/unsound-overlap.stderr @@ -1,5 +1,19 @@ +error[E0283]: type annotations needed: cannot satisfy `&str: A` + --> $DIR/unsound-overlap.rs:10:12 + | +LL | impl A for &str {} + | ^^^^ + | +note: multiple `impl`s satisfying `&str: A` found + --> $DIR/unsound-overlap.rs:9:1 + | +LL | impl A for T {} + | ^^^^^^^^^^^^^^^^^^ +LL | impl A for &str {} + | ^^^^^^^^^^^^^^^ + error[E0119]: conflicting implementations of trait `TraitWithAssoc` for type `((&str,),)` - --> $DIR/unsound-overlap.rs:20:1 + --> $DIR/unsound-overlap.rs:21:1 | LL | impl TraitWithAssoc for T { | ------------------------------- first implementation here @@ -7,6 +21,7 @@ LL | impl TraitWithAssoc for T { LL | impl TraitWithAssoc for ((&str,),) { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `((&str,),)` -error: aborting due to 1 previous error +error: aborting due to 2 previous errors -For more information about this error, try `rustc --explain E0119`. +Some errors have detailed explanations: E0119, E0283. +For more information about an error, try `rustc --explain E0119`. diff --git a/tests/ui/specialization/issue-39448.rs b/tests/ui/specialization/issue-39448.rs index a15c4bd6b7f..1c8843d983a 100644 --- a/tests/ui/specialization/issue-39448.rs +++ b/tests/ui/specialization/issue-39448.rs @@ -22,6 +22,7 @@ trait FromA { } impl> FromA for U { + //~^ ERROR cycle detected when computing whether impls specialize one another default fn from(x: T) -> Self { ToA::to(x) } @@ -42,7 +43,7 @@ fn to(self) -> U { #[allow(dead_code)] fn foo(x: T, y: U) -> U { - x.foo(y.to()).to() //~ ERROR overflow evaluating the requirement + x.foo(y.to()).to() } fn main() { diff --git a/tests/ui/specialization/issue-39448.stderr b/tests/ui/specialization/issue-39448.stderr index dc5db4f4285..e2c5f8c4846 100644 --- a/tests/ui/specialization/issue-39448.stderr +++ b/tests/ui/specialization/issue-39448.stderr @@ -8,28 +8,21 @@ LL | #![feature(specialization)] = help: consider using `min_specialization` instead, which is more stable and complete = note: `#[warn(incomplete_features)]` on by default -error[E0275]: overflow evaluating the requirement `T: FromA` - --> $DIR/issue-39448.rs:45:13 - | -LL | x.foo(y.to()).to() - | ^^ - | -note: required for `T` to implement `FromA` - --> $DIR/issue-39448.rs:24:29 +error[E0391]: cycle detected when computing whether impls specialize one another + --> $DIR/issue-39448.rs:24:1 | LL | impl> FromA for U { - | -------- ^^^^^^^^ ^ - | | - | unsatisfied trait bound introduced here -note: required for `U` to implement `ToA` - --> $DIR/issue-39448.rs:34:12 + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -LL | impl ToA for T - | ^^^^^^ ^ -LL | where -LL | U: FromA, - | -------- unsatisfied trait bound introduced here + = note: ...which requires evaluating trait selection obligation `u16: FromA`... + = note: ...which again requires computing whether impls specialize one another, completing the cycle +note: cycle used when building specialization graph of trait `FromA` + --> $DIR/issue-39448.rs:20:1 + | +LL | trait FromA { + | ^^^^^^^^^^^^^^ + = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information error: aborting due to 1 previous error; 1 warning emitted -For more information about this error, try `rustc --explain E0275`. +For more information about this error, try `rustc --explain E0391`. diff --git a/tests/ui/specialization/issue-39618.rs b/tests/ui/specialization/issue-39618.rs index 5b9b012e665..14a6fcf572e 100644 --- a/tests/ui/specialization/issue-39618.rs +++ b/tests/ui/specialization/issue-39618.rs @@ -2,8 +2,6 @@ // FIXME(JohnTitor): Centril pointed out this looks suspicions, we should revisit here. // More context: https://github.com/rust-lang/rust/pull/69192#discussion_r379846796 -//@ check-pass - #![feature(specialization)] //~ WARN the feature `specialization` is incomplete trait Foo { @@ -19,6 +17,7 @@ fn bar(&self) {} } impl Foo for T where T: Bar { + //~^ ERROR cycle detected when computing whether impls specialize one another fn foo(&self) {} } diff --git a/tests/ui/specialization/issue-39618.stderr b/tests/ui/specialization/issue-39618.stderr index 19de60c7c17..756162ce92c 100644 --- a/tests/ui/specialization/issue-39618.stderr +++ b/tests/ui/specialization/issue-39618.stderr @@ -1,5 +1,5 @@ warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes - --> $DIR/issue-39618.rs:7:12 + --> $DIR/issue-39618.rs:5:12 | LL | #![feature(specialization)] | ^^^^^^^^^^^^^^ @@ -8,5 +8,21 @@ LL | #![feature(specialization)] = help: consider using `min_specialization` instead, which is more stable and complete = note: `#[warn(incomplete_features)]` on by default -warning: 1 warning emitted +error[E0391]: cycle detected when computing whether impls specialize one another + --> $DIR/issue-39618.rs:19:1 + | +LL | impl Foo for T where T: Bar { + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | + = note: ...which requires evaluating trait selection obligation `u64: Bar`... + = note: ...which again requires computing whether impls specialize one another, completing the cycle +note: cycle used when building specialization graph of trait `Foo` + --> $DIR/issue-39618.rs:7:1 + | +LL | trait Foo { + | ^^^^^^^^^ + = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information +error: aborting due to 1 previous error; 1 warning emitted + +For more information about this error, try `rustc --explain E0391`. diff --git a/tests/ui/traits/stack-error-order-dependence-2.rs b/tests/ui/traits/stack-error-order-dependence-2.rs new file mode 100644 index 00000000000..323685aa15b --- /dev/null +++ b/tests/ui/traits/stack-error-order-dependence-2.rs @@ -0,0 +1,24 @@ +//@ check-pass +// Regression test for . +// This time EXCEPT without `dyn` builtin bounds :^) + +pub trait Trait: Supertrait {} + +trait Impossible {} +impl Trait for F {} + +pub trait Supertrait {} + +impl Supertrait for T {} + +fn needs_supertrait() {} +fn needs_trait() {} + +struct A; +impl Trait for A where A: Supertrait {} +impl Supertrait for A {} + +fn main() { + needs_supertrait::(); + needs_trait::(); +} diff --git a/tests/ui/traits/stack-error-order-dependence.rs b/tests/ui/traits/stack-error-order-dependence.rs new file mode 100644 index 00000000000..037c292a542 --- /dev/null +++ b/tests/ui/traits/stack-error-order-dependence.rs @@ -0,0 +1,19 @@ +//@ check-pass +// Regression test for . + +pub trait Trait: Supertrait {} + +trait Impossible {} +impl Trait for F {} + +pub trait Supertrait {} + +impl Supertrait for T {} + +fn needs_supertrait() {} +fn needs_trait() {} + +fn main() { + needs_supertrait::(); + needs_trait::(); +}