From cf224ea1fbe2fb7eb64812288338a2c4cfe1d084 Mon Sep 17 00:00:00 2001 From: Michael Goulet Date: Mon, 28 Apr 2025 18:16:34 +0000 Subject: [PATCH] incompletely prefer opaque type bounds when self type bottoms out in infer --- compiler/rustc_middle/src/ty/context.rs | 6 +- .../src/solve/assembly/mod.rs | 137 +++++++++++++++++- .../src/solve/effect_goals.rs | 3 +- .../src/solve/eval_ctxt/mod.rs | 31 ++++ .../src/solve/normalizes_to/mod.rs | 7 +- .../src/solve/trait_goals.rs | 3 +- compiler/rustc_type_ir/src/interner.rs | 1 + ...nce-constraints-from-blanket-2.next.stderr | 16 ++ ...id-inference-constraints-from-blanket-2.rs | 31 ++++ ...id-inference-constraints-from-blanket-3.rs | 25 ++++ ...nference-constraints-from-blanket-3.stderr | 25 ++++ ...void-inference-constraints-from-blanket.rs | 25 ++++ .../multiple-opaques-ambig.rs | 23 +++ .../non-defining-uses/multiple-opaques-ok.rs | 37 +++++ .../non-defining-uses/no-rigid-alias.rs | 27 ++++ .../non-defining-uses/use-blanket-impl.rs | 19 +++ .../use-item-bound-over-blanket-impl.rs | 30 ++++ .../non-defining-uses/use-item-bound.rs | 25 ++++ 18 files changed, 457 insertions(+), 14 deletions(-) create mode 100644 tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.next.stderr create mode 100644 tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.stderr create mode 100644 tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/multiple-opaques-ambig.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/multiple-opaques-ok.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/no-rigid-alias.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/use-blanket-impl.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/use-item-bound-over-blanket-impl.rs create mode 100644 tests/ui/impl-trait/non-defining-uses/use-item-bound.rs diff --git a/compiler/rustc_middle/src/ty/context.rs b/compiler/rustc_middle/src/ty/context.rs index 218ac2cfbc19..8ea767dccd3b 100644 --- a/compiler/rustc_middle/src/ty/context.rs +++ b/compiler/rustc_middle/src/ty/context.rs @@ -651,7 +651,11 @@ impl<'tcx> Interner for TyCtxt<'tcx> { | ty::Bound(_, _) => bug!("unexpected self type: {self_ty}"), } - let trait_impls = tcx.trait_impls_of(trait_def_id); + #[allow(rustc::usage_of_type_ir_traits)] + self.for_each_blanket_impl(trait_def_id, f) + } + fn for_each_blanket_impl(self, trait_def_id: DefId, mut f: impl FnMut(DefId)) { + let trait_impls = self.trait_impls_of(trait_def_id); for &impl_def_id in trait_impls.blanket_impls() { f(impl_def_id); } diff --git a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs index e3cf0330b14a..fb777496e31e 100644 --- a/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/assembly/mod.rs @@ -11,8 +11,9 @@ use rustc_type_ir::lang_items::SolverTraitLangItem; use rustc_type_ir::search_graph::CandidateHeadUsages; use rustc_type_ir::solve::SizedTraitKind; use rustc_type_ir::{ - self as ty, Interner, TypeFlags, TypeFoldable, TypeSuperVisitable, TypeVisitable, - TypeVisitableExt as _, TypeVisitor, TypingMode, Upcast as _, elaborate, + self as ty, Interner, TypeFlags, TypeFoldable, TypeFolder, TypeSuperFoldable, + TypeSuperVisitable, TypeVisitable, TypeVisitableExt, TypeVisitor, TypingMode, Upcast, + elaborate, }; use tracing::{debug, instrument}; @@ -187,6 +188,7 @@ where ecx: &mut EvalCtxt<'_, D>, goal: Goal, impl_def_id: I::ImplId, + then: impl FnOnce(&mut EvalCtxt<'_, D>, Certainty) -> QueryResult, ) -> Result, NoSolution>; /// If the predicate contained an error, we want to avoid emitting unnecessary trait @@ -365,6 +367,15 @@ pub(super) enum AssembleCandidatesFrom { EnvAndBounds, } +impl AssembleCandidatesFrom { + fn should_assemble_impl_candidates(&self) -> bool { + match self { + AssembleCandidatesFrom::All => true, + AssembleCandidatesFrom::EnvAndBounds => false, + } + } +} + /// This is currently used to track the [CandidateHeadUsages] of all failed `ParamEnv` /// candidates. This is then used to ignore their head usages in case there's another /// always applicable `ParamEnv` candidate. Look at how `param_env_head_usages` is @@ -397,14 +408,15 @@ where return (candidates, failed_candidate_info); }; + let goal: Goal = goal + .with(self.cx(), goal.predicate.with_replaced_self_ty(self.cx(), normalized_self_ty)); + if normalized_self_ty.is_ty_var() { debug!("self type has been normalized to infer"); - candidates.extend(self.forced_ambiguity(MaybeCause::Ambiguity)); + self.try_assemble_bounds_via_registered_opaques(goal, assemble_from, &mut candidates); return (candidates, failed_candidate_info); } - let goal: Goal = goal - .with(self.cx(), goal.predicate.with_replaced_self_ty(self.cx(), normalized_self_ty)); // Vars that show up in the rest of the goal substs may have been constrained by // normalizing the self type as well, since type variables are not uniquified. let goal = self.resolve_vars_if_possible(goal); @@ -484,8 +496,9 @@ where if cx.impl_is_default(impl_def_id) { return; } - - match G::consider_impl_candidate(self, goal, impl_def_id) { + match G::consider_impl_candidate(self, goal, impl_def_id, |ecx, certainty| { + ecx.evaluate_added_goals_and_make_canonical_response(certainty) + }) { Ok(candidate) => candidates.push(candidate), Err(NoSolution) => (), } @@ -943,6 +956,116 @@ where } } + /// If the self type is the hidden type of an opaque, try to assemble + /// candidates for it by consider its item bounds and by using blanket + /// impls. This is used to incompletely guide type inference when handling + /// non-defining uses in the defining scope. + /// + /// We otherwise just fail fail with ambiguity. Even if we're using an + /// opaque type item bound or a blank impls, we still force its certainty + /// to be `Maybe` so that we properly prove this goal later. + /// + /// See + /// for why this is necessary. + fn try_assemble_bounds_via_registered_opaques>( + &mut self, + goal: Goal, + assemble_from: AssembleCandidatesFrom, + candidates: &mut Vec>, + ) { + let self_ty = goal.predicate.self_ty(); + // If the self type is sub unified with any opaque type, we + // also look at blanket impls for it. + let mut assemble_blanket_impls = false; + for alias_ty in self.opaques_with_sub_unified_hidden_type(self_ty) { + assemble_blanket_impls = true; + debug!("self ty is sub unified with {alias_ty:?}"); + + struct ReplaceOpaque { + cx: I, + alias_ty: ty::AliasTy, + self_ty: I::Ty, + } + impl TypeFolder for ReplaceOpaque { + fn cx(&self) -> I { + self.cx + } + fn fold_ty(&mut self, ty: I::Ty) -> I::Ty { + if let ty::Alias(ty::Opaque, alias_ty) = ty.kind() { + if alias_ty == self.alias_ty { + return self.self_ty; + } + } + ty.super_fold_with(self) + } + } + + // We look at all item-bounds of the opaque, replacing the + // opaque with the current self type before considering + // them as a candidate. Imagine e've got `?x: Trait` + // and `?x` has been sub-unified with the hidden type of + // `impl Trait`, We take the item bound `opaque: Trait` + // and replace all occurrences of `opaque` with `?x`. This results + // in a `?x: Trait` alias-bound candidate. + for item_bound in self + .cx() + .item_self_bounds(alias_ty.def_id) + .iter_instantiated(self.cx(), alias_ty.args) + { + let assumption = + item_bound.fold_with(&mut ReplaceOpaque { cx: self.cx(), alias_ty, self_ty }); + candidates.extend(G::probe_and_match_goal_against_assumption( + self, + CandidateSource::AliasBound, + goal, + assumption, + |ecx| { + // We want to reprove this goal once we've inferred the + // hidden type, so we force the certainty to `Maybe`. + ecx.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) + }, + )); + } + } + + // We also need to consider blanket impls for not-yet-defined opaque types. + // + // See tests/ui/impl-trait/non-defining-uses/use-blanket-impl.rs for an example. + if assemble_blanket_impls && assemble_from.should_assemble_impl_candidates() { + let cx = self.cx(); + cx.for_each_blanket_impl(goal.predicate.trait_def_id(cx), |impl_def_id| { + // For every `default impl`, there's always a non-default `impl` + // that will *also* apply. There's no reason to register a candidate + // for this impl, since it is *not* proof that the trait goal holds. + if cx.impl_is_default(impl_def_id) { + return; + } + + match G::consider_impl_candidate(self, goal, impl_def_id, |ecx, certainty| { + if ecx.shallow_resolve(self_ty).is_ty_var() { + // We force the certainty of impl candidates to be `Maybe`. + let certainty = certainty.and(Certainty::AMBIGUOUS); + ecx.evaluate_added_goals_and_make_canonical_response(certainty) + } else { + // We don't want to use impls if they constrain the opaque. + // + // FIXME(trait-system-refactor-initiative#229): This isn't + // perfect yet as it still allows us to incorrectly constrain + // other inference variables. + Err(NoSolution) + } + }) { + Ok(candidate) => candidates.push(candidate), + Err(NoSolution) => (), + } + }); + } + + if candidates.is_empty() { + candidates.extend(self.forced_ambiguity(MaybeCause::Ambiguity)); + } + } + /// Assemble and merge candidates for goals which are related to an underlying trait /// goal. Right now, this is normalizes-to and host effect goals. /// diff --git a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs index 6646857a1368..cb72c1cd92b8 100644 --- a/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs +++ b/compiler/rustc_next_trait_solver/src/solve/effect_goals.rs @@ -124,6 +124,7 @@ where ecx: &mut EvalCtxt<'_, D>, goal: Goal, impl_def_id: I::ImplId, + then: impl FnOnce(&mut EvalCtxt<'_, D>, Certainty) -> QueryResult, ) -> Result, NoSolution> { let cx = ecx.cx(); @@ -175,7 +176,7 @@ where }); ecx.add_goals(GoalSource::ImplWhereBound, const_conditions); - ecx.evaluate_added_goals_and_make_canonical_response(certainty) + then(ecx, certainty) }) } diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs index f1c1801dd3f1..3e3a5246f3d7 100644 --- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs @@ -1060,6 +1060,10 @@ where self.delegate.resolve_vars_if_possible(value) } + pub(super) fn shallow_resolve(&self, ty: I::Ty) -> I::Ty { + self.delegate.shallow_resolve(ty) + } + pub(super) fn eager_resolve_region(&self, r: I::Region) -> I::Region { if let ty::ReVar(vid) = r.kind() { self.delegate.opportunistic_resolve_lt_var(vid) @@ -1176,6 +1180,33 @@ where ) -> bool { may_use_unstable_feature(&**self.delegate, param_env, symbol) } + + pub(crate) fn opaques_with_sub_unified_hidden_type( + &self, + self_ty: I::Ty, + ) -> impl Iterator> + use<'a, D, I> { + let delegate = self.delegate; + delegate + .clone_opaque_types_lookup_table() + .into_iter() + .chain(delegate.clone_duplicate_opaque_types()) + .filter_map(move |(key, hidden_ty)| { + if let ty::Infer(ty::TyVar(self_vid)) = self_ty.kind() { + if let ty::Infer(ty::TyVar(hidden_vid)) = hidden_ty.kind() { + if delegate.sub_unification_table_root_var(self_vid) + == delegate.sub_unification_table_root_var(hidden_vid) + { + return Some(ty::AliasTy::new_from_args( + delegate.cx(), + key.def_id.into(), + key.args, + )); + } + } + } + None + }) + } } /// Eagerly replace aliases with inference variables, emitting `AliasRelate` diff --git a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs index 6e6be829f521..54b92ebac1de 100644 --- a/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/normalizes_to/mod.rs @@ -194,6 +194,7 @@ where ecx: &mut EvalCtxt<'_, D>, goal: Goal>, impl_def_id: I::ImplId, + then: impl FnOnce(&mut EvalCtxt<'_, D>, Certainty) -> QueryResult, ) -> Result, NoSolution> { let cx = ecx.cx(); @@ -314,8 +315,7 @@ where // nested goal for consistency. ty::TypingMode::Coherence => { ecx.add_goal(GoalSource::Misc, goal.with(cx, PredicateKind::Ambiguous)); - return ecx - .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); + return then(ecx, Certainty::Yes); } ty::TypingMode::Analysis { .. } | ty::TypingMode::Borrowck { .. } @@ -325,8 +325,7 @@ where goal, goal.predicate.alias, ); - return ecx - .evaluate_added_goals_and_make_canonical_response(Certainty::Yes); + return then(ecx, Certainty::Yes); } } } else { diff --git a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs index 3e720a47f32e..a69e867289ce 100644 --- a/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs +++ b/compiler/rustc_next_trait_solver/src/solve/trait_goals.rs @@ -55,6 +55,7 @@ where ecx: &mut EvalCtxt<'_, D>, goal: Goal>, impl_def_id: I::ImplId, + then: impl FnOnce(&mut EvalCtxt<'_, D>, Certainty) -> QueryResult, ) -> Result, NoSolution> { let cx = ecx.cx(); @@ -112,7 +113,7 @@ where .map(|pred| goal.with(cx, pred)), ); - ecx.evaluate_added_goals_and_make_canonical_response(maximal_certainty) + then(ecx, maximal_certainty) }) } diff --git a/compiler/rustc_type_ir/src/interner.rs b/compiler/rustc_type_ir/src/interner.rs index 3a83b1739ffa..cf58aec14a68 100644 --- a/compiler/rustc_type_ir/src/interner.rs +++ b/compiler/rustc_type_ir/src/interner.rs @@ -347,6 +347,7 @@ pub trait Interner: self_ty: Self::Ty, f: impl FnMut(Self::ImplId), ); + fn for_each_blanket_impl(self, trait_def_id: Self::TraitId, f: impl FnMut(Self::ImplId)); fn has_item_definition(self, def_id: Self::DefId) -> bool; diff --git a/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.next.stderr b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.next.stderr new file mode 100644 index 000000000000..86ac1bdad041 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.next.stderr @@ -0,0 +1,16 @@ +error[E0308]: mismatched types + --> $DIR/avoid-inference-constraints-from-blanket-2.rs:27:18 + | +LL | let _: u32 = x; + | --- ^ expected `u32`, found `u64` + | | + | expected due to this + | +help: you can convert a `u64` to a `u32` and panic if the converted value doesn't fit + | +LL | let _: u32 = x.try_into().unwrap(); + | ++++++++++++++++++++ + +error: aborting due to 1 previous error + +For more information about this error, try `rustc --explain E0308`. diff --git a/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.rs b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.rs new file mode 100644 index 000000000000..b4f853de4aad --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-2.rs @@ -0,0 +1,31 @@ +//@ revisions: current next +//@[next] compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@[current] check-pass + +// Regression test for trait-system-refactor-initiative#205. Avoid +// constraining other impl arguments when applying blanket impls. + +// FIXME(-Znext-solver): This currently incompletely constrains the +// argument of `opaque: Trait` using the blanket impl of trait. +// Ideally we don't do that. + +trait Trait {} + +impl Trait for T {} +impl Trait for u64 {} + +fn impls_trait, U>(_: U) -> T { + todo!() +} + +fn foo() -> impl Sized { + let x = Default::default(); + if false { + return impls_trait::<_, _>(x); + } + let _: u32 = x; + //[next]~^ ERROR mismatched types + 1u64 +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.rs b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.rs new file mode 100644 index 000000000000..2f29cb4ee6b4 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.rs @@ -0,0 +1,25 @@ +//@ compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +#![allow(unconditional_recursion)] + +// Regression test for trait-system-refactor-initiative#205. Avoid +// constraining other impl arguments when applying blanket impls, +// especially if the nested where-bounds of the blanket impl don't +// actually apply for the opaque. + +// FIXME(-Znext-solver): This currently incompletely constrains the +// argument of `opaque: Trait` using the blanket impl of trait. +// Ideally we don't do that. + +trait Trait {} + +impl Trait for T {} +impl Trait for String {} +fn impls_trait, U>(_: T) {} + +fn test() -> impl Sized { + let x = test(); + impls_trait(x); //~ ERROR the trait bound `String: Trait` is not satisfied + String::new() +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.stderr b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.stderr new file mode 100644 index 000000000000..a5d19b484811 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket-3.stderr @@ -0,0 +1,25 @@ +error[E0277]: the trait bound `String: Trait` is not satisfied + --> $DIR/avoid-inference-constraints-from-blanket-3.rs:22:5 + | +LL | impls_trait(x); + | ^^^^^^^^^^^^^^ the trait `Copy` is not implemented for `String` + | + = help: the trait `Trait` is not implemented for `String` + but trait `Trait` is implemented for it + = help: for that trait implementation, expected `u64`, found `u32` +note: required for `String` to implement `Trait` + --> $DIR/avoid-inference-constraints-from-blanket-3.rs:16:15 + | +LL | impl Trait for T {} + | ---- ^^^^^^^^^^ ^ + | | + | unsatisfied trait bound introduced here +note: required by a bound in `impls_trait` + --> $DIR/avoid-inference-constraints-from-blanket-3.rs:18:19 + | +LL | fn impls_trait, U>(_: T) {} + | ^^^^^^^^ required by this bound in `impls_trait` + +error: aborting due to 1 previous error + +For more information about this error, try `rustc --explain E0277`. diff --git a/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket.rs b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket.rs new file mode 100644 index 000000000000..bb3acfde5bc8 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/avoid-inference-constraints-from-blanket.rs @@ -0,0 +1,25 @@ +//@ revisions: current next +//@[next] compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass + +// Regression test for trait-system-refactor-initiative#205. Avoid constraining +// the opaque type when applying blanket impls. + +trait Trait {} + +impl Trait for T {} +impl Trait for u64 {} + +fn impls_trait, U>() -> T { + todo!() +} + +fn foo() -> impl Sized { + if false { + // `opaque: Trait` shouldn't constrain `opaque` to `u32` via the blanket impl + return impls_trait::<_, u32>(); + } + 1u64 +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/multiple-opaques-ambig.rs b/tests/ui/impl-trait/non-defining-uses/multiple-opaques-ambig.rs new file mode 100644 index 000000000000..e7aaf6fa135a --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/multiple-opaques-ambig.rs @@ -0,0 +1,23 @@ +//@ compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass +#![allow(unconditional_recursion)] + +// Regression test for trait-system-refactor-initiative#182. If multiple +// opaque types result in different item bounds, do not apply them. + +trait Trait {} +impl Trait for U {} + +fn impls_trait, U>(_: T) -> U { + todo!() +} + +fn overlap() -> (impl Trait, impl Trait) { + let mut x = overlap::().0; + x = overlap::().1; + let u = impls_trait(x); + let _: u32 = u; + ((), ()) +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/multiple-opaques-ok.rs b/tests/ui/impl-trait/non-defining-uses/multiple-opaques-ok.rs new file mode 100644 index 000000000000..d91efe181e35 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/multiple-opaques-ok.rs @@ -0,0 +1,37 @@ +//@ compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass +#![allow(unconditional_recursion)] + +// Regression test for trait-system-refactor-initiative#18, making sure +// we support being sub unified with more than 1 opaque type. + +trait Id { + type This; +} +impl Id for &'static str { + type This = &'static str; +} +fn to_assoc(x: T) -> ::This { + todo!() +} + +fn mirror1() -> (impl Id, impl Sized) { + let mut opaque = mirror1().0; + opaque = mirror1().1; + let x = to_assoc(opaque); + // `?x` equals both opaques, make sure we still use the applicable + // item bound. + x.len(); + (x, x) +} +fn mirror2() -> (impl Sized, impl Id) { + let mut opaque = mirror2().0; + opaque = mirror2().1; + let x = to_assoc(opaque); + // `?x` equals both opaques, make sure we still use the applicable + // item bound. + x.len(); + (x, x) +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/no-rigid-alias.rs b/tests/ui/impl-trait/non-defining-uses/no-rigid-alias.rs new file mode 100644 index 000000000000..fca5db3e20f8 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/no-rigid-alias.rs @@ -0,0 +1,27 @@ +//@ compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass +#![allow(unconditional_recursion)] + +// Test for trait-system-refactor-initiative#182 making sure +// that we don't incorrectly normalize to rigid aliases if the +// opaque type only has a trait bound. + +trait Id { + type This; +} +impl Id for Vec { + type This = Vec; +} +fn to_assoc(x: T) -> ::This { + todo!() +} + +fn mirror(x: Vec) -> impl Id { + let x = to_assoc(mirror(x)); + // `?x` equals ` as Id>::This`. We should not infer `?x` + // to be a rigid alias here. + let _: Vec = x; + x +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/use-blanket-impl.rs b/tests/ui/impl-trait/non-defining-uses/use-blanket-impl.rs new file mode 100644 index 000000000000..50bb3995b944 --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/use-blanket-impl.rs @@ -0,0 +1,19 @@ +//@ revisions: current next +//@[next] compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass + +// Regression test for trait-system-refactor-initiative#196. +fn iterator(b: bool) -> impl Iterator { + if b { + // We need to eagerly figure out the type of `i` here by using + // the `::Item` obligation. This means + // we not only have to consider item bounds, but also blanket impls. + for i in iterator(false) { + i.len(); + } + } + + vec![].into_iter() +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/use-item-bound-over-blanket-impl.rs b/tests/ui/impl-trait/non-defining-uses/use-item-bound-over-blanket-impl.rs new file mode 100644 index 000000000000..7c2766ade3fa --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/use-item-bound-over-blanket-impl.rs @@ -0,0 +1,30 @@ +//@ revisions: current next +//@[next] compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass +#![allow(unconditional_recursion)] + +// Regression test for trait-system-refactor-initiative#182. + +trait Id { + type This; +} +impl Id for T { + type This = T; +} +fn to_assoc(x: T) -> ::This { + x +} + +fn mirror(x: Vec) -> impl Id> { + let x = to_assoc(mirror(x)); + // `?x` equals ` as Id>::This`. We need to eagerly infer the + // type of `?x` to prevent this method call from resulting in an error. + // + // We could use both the item bound to normalize to `Vec`, or the + // blanket impl to normalize to `opaque::`. We have to go with the + // item bound. + x.len(); + x +} +fn main() {} diff --git a/tests/ui/impl-trait/non-defining-uses/use-item-bound.rs b/tests/ui/impl-trait/non-defining-uses/use-item-bound.rs new file mode 100644 index 000000000000..36dcbacbe6fd --- /dev/null +++ b/tests/ui/impl-trait/non-defining-uses/use-item-bound.rs @@ -0,0 +1,25 @@ +//@ revisions: current next +//@[next] compile-flags: -Znext-solver +//@ ignore-compare-mode-next-solver (explicit revisions) +//@ check-pass +#![allow(unconditional_recursion)] +// Regression test for trait-system-refactor-initiative#182. + +trait Id { + type This; +} +impl Id for Vec { + type This = Vec; +} +fn to_assoc(x: T) -> ::This { + todo!() +} + +fn mirror(x: Vec) -> impl Id> { + let x = to_assoc(mirror(x)); + // `?x` equals ` as Id>::This`. We need to eagerly infer the + // type of `?x` to prevent this method call from resulting in an error. + x.len(); + x +} +fn main() {}