From 0b323eacd4c4cf99d18bd75ad02b2139dd990297 Mon Sep 17 00:00:00 2001 From: lcnr Date: Thu, 24 Jul 2025 14:53:13 +0000 Subject: uniquify root goals during HIR typeck --- compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs | 7 ++- compiler/rustc_infer/src/infer/at.rs | 2 + compiler/rustc_infer/src/infer/context.rs | 4 ++ compiler/rustc_infer/src/infer/mod.rs | 38 +++++++++++- .../rustc_next_trait_solver/src/canonicalizer.rs | 72 +++++++++++++++------- .../src/solve/eval_ctxt/canonical.rs | 2 + .../src/solve/eval_ctxt/mod.rs | 5 +- compiler/rustc_next_trait_solver/src/solve/mod.rs | 2 - compiler/rustc_type_ir/src/infer_ctxt.rs | 4 ++ 9 files changed, 107 insertions(+), 29 deletions(-) (limited to 'compiler') diff --git a/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs b/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs index 9f4ab8ca5d4..20844dee793 100644 --- a/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs +++ b/compiler/rustc_hir_typeck/src/typeck_root_ctxt.rs @@ -85,8 +85,11 @@ impl<'tcx> TypeckRootCtxt<'tcx> { pub(crate) fn new(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> Self { let hir_owner = tcx.local_def_id_to_hir_id(def_id).owner; - let infcx = - tcx.infer_ctxt().ignoring_regions().build(TypingMode::typeck_for_body(tcx, def_id)); + let infcx = tcx + .infer_ctxt() + .ignoring_regions() + .in_hir_typeck() + .build(TypingMode::typeck_for_body(tcx, def_id)); let typeck_results = RefCell::new(ty::TypeckResults::new(hir_owner)); let fulfillment_cx = RefCell::new(>::new(&infcx)); diff --git a/compiler/rustc_infer/src/infer/at.rs b/compiler/rustc_infer/src/infer/at.rs index 5fe795bd23a..ad19cdef4e7 100644 --- a/compiler/rustc_infer/src/infer/at.rs +++ b/compiler/rustc_infer/src/infer/at.rs @@ -71,6 +71,7 @@ impl<'tcx> InferCtxt<'tcx> { tcx: self.tcx, typing_mode: self.typing_mode, considering_regions: self.considering_regions, + in_hir_typeck: self.in_hir_typeck, skip_leak_check: self.skip_leak_check, inner: self.inner.clone(), lexical_region_resolutions: self.lexical_region_resolutions.clone(), @@ -95,6 +96,7 @@ impl<'tcx> InferCtxt<'tcx> { tcx: self.tcx, typing_mode, considering_regions: self.considering_regions, + in_hir_typeck: self.in_hir_typeck, skip_leak_check: self.skip_leak_check, inner: self.inner.clone(), lexical_region_resolutions: self.lexical_region_resolutions.clone(), diff --git a/compiler/rustc_infer/src/infer/context.rs b/compiler/rustc_infer/src/infer/context.rs index bb9c8850093..21e999b080d 100644 --- a/compiler/rustc_infer/src/infer/context.rs +++ b/compiler/rustc_infer/src/infer/context.rs @@ -22,6 +22,10 @@ impl<'tcx> rustc_type_ir::InferCtxtLike for InferCtxt<'tcx> { self.next_trait_solver } + fn in_hir_typeck(&self) -> bool { + self.in_hir_typeck + } + fn typing_mode(&self) -> ty::TypingMode<'tcx> { self.typing_mode() } diff --git a/compiler/rustc_infer/src/infer/mod.rs b/compiler/rustc_infer/src/infer/mod.rs index 2d269e320b6..17c587c5e7f 100644 --- a/compiler/rustc_infer/src/infer/mod.rs +++ b/compiler/rustc_infer/src/infer/mod.rs @@ -244,9 +244,28 @@ pub struct InferCtxt<'tcx> { typing_mode: TypingMode<'tcx>, /// Whether this inference context should care about region obligations in - /// the root universe. Most notably, this is used during hir typeck as region + /// the root universe. Most notably, this is used during HIR typeck as region /// solving is left to borrowck instead. pub considering_regions: bool, + /// Whether this inference context is used by HIR typeck. If so, we uniquify regions + /// with `-Znext-solver`. This is necessary as borrowck will start by replacing each + /// occurance of a free region with a unique inference variable so if HIR typeck + /// ends up depending on two regions being equal we'd get unexpected mismatches + /// between HIR typeck and MIR typeck, resulting in an ICE. + /// + /// The trait solver sometimes depends on regions being identical. As a concrete example + /// the trait solver ignores other candidates if one candidate exists without any constraints. + /// The goal `&'a u32: Equals<&'a u32>` has no constraints right now, but if we replace + /// each occurance of `'a` with a unique region the goal now equates these regions. + /// + /// See the tests in trait-system-refactor-initiative#27 for concrete examples. + /// + /// FIXME(-Znext-solver): This is insufficient in theory as a goal `T: Trait` + /// may rely on the two occurances of `?x` being identical. If `?x` gets inferred to a + /// type containing regions, this will no longer be the case. We can handle this case + /// by storing goals which hold while still depending on inference vars and then + /// reproving them before writeback. + pub in_hir_typeck: bool, /// If set, this flag causes us to skip the 'leak check' during /// higher-ranked subtyping operations. This flag is a temporary one used @@ -506,6 +525,7 @@ pub struct TypeOutlivesConstraint<'tcx> { pub struct InferCtxtBuilder<'tcx> { tcx: TyCtxt<'tcx>, considering_regions: bool, + in_hir_typeck: bool, skip_leak_check: bool, /// Whether we should use the new trait solver in the local inference context, /// which affects things like which solver is used in `predicate_may_hold`. @@ -518,6 +538,7 @@ impl<'tcx> TyCtxt<'tcx> { InferCtxtBuilder { tcx: self, considering_regions: true, + in_hir_typeck: false, skip_leak_check: false, next_trait_solver: self.next_trait_solver_globally(), } @@ -535,6 +556,11 @@ impl<'tcx> InferCtxtBuilder<'tcx> { self } + pub fn in_hir_typeck(mut self) -> Self { + self.in_hir_typeck = true; + self + } + pub fn skip_leak_check(mut self, skip_leak_check: bool) -> Self { self.skip_leak_check = skip_leak_check; self @@ -568,12 +594,18 @@ impl<'tcx> InferCtxtBuilder<'tcx> { } pub fn build(&mut self, typing_mode: TypingMode<'tcx>) -> InferCtxt<'tcx> { - let InferCtxtBuilder { tcx, considering_regions, skip_leak_check, next_trait_solver } = - *self; + let InferCtxtBuilder { + tcx, + considering_regions, + in_hir_typeck, + skip_leak_check, + next_trait_solver, + } = *self; InferCtxt { tcx, typing_mode, considering_regions, + in_hir_typeck, skip_leak_check, inner: RefCell::new(InferCtxtInner::new()), lexical_region_resolutions: RefCell::new(None), diff --git a/compiler/rustc_next_trait_solver/src/canonicalizer.rs b/compiler/rustc_next_trait_solver/src/canonicalizer.rs index a418aa82100..1bc35e599c7 100644 --- a/compiler/rustc_next_trait_solver/src/canonicalizer.rs +++ b/compiler/rustc_next_trait_solver/src/canonicalizer.rs @@ -19,6 +19,20 @@ const NEEDS_CANONICAL: TypeFlags = TypeFlags::from_bits( ) .unwrap(); +#[derive(Debug, Clone, Copy)] +enum CanonicalizeInputKind { + /// When canonicalizing the `param_env`, we keep `'static` as merging + /// trait candidates relies on it when deciding whether a where-bound + /// is trivial. + ParamEnv, + /// When canonicalizing predicates, we don't keep `'static`. If we're + /// currently outside of the trait solver and canonicalize the root goal + /// during HIR typeck, we replace each occurance of a region with a + /// unique region variable. See the comment on `InferCtxt::in_hir_typeck` + /// for more details. + Predicate { is_hir_typeck_root_goal: bool }, +} + /// Whether we're canonicalizing a query input or the query response. /// /// When canonicalizing an input we're in the context of the caller @@ -26,10 +40,7 @@ const NEEDS_CANONICAL: TypeFlags = TypeFlags::from_bits( /// query. #[derive(Debug, Clone, Copy)] enum CanonicalizeMode { - /// When canonicalizing the `param_env`, we keep `'static` as merging - /// trait candidates relies on it when deciding whether a where-bound - /// is trivial. - Input { keep_static: bool }, + Input(CanonicalizeInputKind), /// FIXME: We currently return region constraints referring to /// placeholders and inference variables from a binder instantiated /// inside of the query. @@ -122,7 +133,7 @@ impl<'a, D: SolverDelegate, I: Interner> Canonicalizer<'a, D, I> { let mut variables = Vec::new(); let mut env_canonicalizer = Canonicalizer { delegate, - canonicalize_mode: CanonicalizeMode::Input { keep_static: true }, + canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv), variables: &mut variables, variable_lookup_table: Default::default(), @@ -154,7 +165,7 @@ impl<'a, D: SolverDelegate, I: Interner> Canonicalizer<'a, D, I> { } else { let mut env_canonicalizer = Canonicalizer { delegate, - canonicalize_mode: CanonicalizeMode::Input { keep_static: true }, + canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv), variables, variable_lookup_table: Default::default(), @@ -180,6 +191,7 @@ impl<'a, D: SolverDelegate, I: Interner> Canonicalizer<'a, D, I> { pub fn canonicalize_input>( delegate: &'a D, variables: &'a mut Vec, + is_hir_typeck_root_goal: bool, input: QueryInput, ) -> ty::Canonical> { // First canonicalize the `param_env` while keeping `'static` @@ -189,7 +201,9 @@ impl<'a, D: SolverDelegate, I: Interner> Canonicalizer<'a, D, I> { // while *mostly* reusing the canonicalizer from above. let mut rest_canonicalizer = Canonicalizer { delegate, - canonicalize_mode: CanonicalizeMode::Input { keep_static: false }, + canonicalize_mode: CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { + is_hir_typeck_root_goal, + }), variables, variable_lookup_table, @@ -296,7 +310,7 @@ impl<'a, D: SolverDelegate, I: Interner> Canonicalizer<'a, D, I> { } } - fn cached_fold_ty(&mut self, t: I::Ty) -> I::Ty { + fn inner_fold_ty(&mut self, t: I::Ty) -> I::Ty { let kind = match t.kind() { ty::Infer(i) => match i { ty::TyVar(vid) => { @@ -413,10 +427,10 @@ impl, I: Interner> TypeFolder for Canonicaliz // We don't canonicalize `ReStatic` in the `param_env` as we use it // when checking whether a `ParamEnv` candidate is global. ty::ReStatic => match self.canonicalize_mode { - CanonicalizeMode::Input { keep_static: false } => { + CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { .. }) => { CanonicalVarKind::Region(ty::UniverseIndex::ROOT) } - CanonicalizeMode::Input { keep_static: true } + CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv) | CanonicalizeMode::Response { .. } => return r, }, @@ -428,12 +442,12 @@ impl, I: Interner> TypeFolder for Canonicaliz // `ReErased`. We may be able to short-circuit registering region // obligations if we encounter a `ReErased` on one side, for example. ty::ReErased | ty::ReError(_) => match self.canonicalize_mode { - CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), + CanonicalizeMode::Input(_) => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), CanonicalizeMode::Response { .. } => return r, }, ty::ReEarlyParam(_) | ty::ReLateParam(_) => match self.canonicalize_mode { - CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), + CanonicalizeMode::Input(_) => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), CanonicalizeMode::Response { .. } => { panic!("unexpected region in response: {r:?}") } @@ -441,7 +455,7 @@ impl, I: Interner> TypeFolder for Canonicaliz ty::RePlaceholder(placeholder) => match self.canonicalize_mode { // We canonicalize placeholder regions as existentials in query inputs. - CanonicalizeMode::Input { .. } => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), + CanonicalizeMode::Input(_) => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), CanonicalizeMode::Response { max_input_universe } => { // If we have a placeholder region inside of a query, it must be from // a new universe. @@ -459,9 +473,7 @@ impl, I: Interner> TypeFolder for Canonicaliz "region vid should have been resolved fully before canonicalization" ); match self.canonicalize_mode { - CanonicalizeMode::Input { keep_static: _ } => { - CanonicalVarKind::Region(ty::UniverseIndex::ROOT) - } + CanonicalizeMode::Input(_) => CanonicalVarKind::Region(ty::UniverseIndex::ROOT), CanonicalizeMode::Response { .. } => { CanonicalVarKind::Region(self.delegate.universe_of_lt(vid).unwrap()) } @@ -469,16 +481,34 @@ impl, I: Interner> TypeFolder for Canonicaliz } }; - let var = self.get_or_insert_bound_var(r, kind); + let var = if let CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { + is_hir_typeck_root_goal: true, + }) = self.canonicalize_mode + { + let var = ty::BoundVar::from(self.variables.len()); + self.variables.push(r.into()); + self.var_kinds.push(kind); + var + } else { + self.get_or_insert_bound_var(r, kind) + }; Region::new_anon_bound(self.cx(), self.binder_index, var) } fn fold_ty(&mut self, t: I::Ty) -> I::Ty { - if let Some(&ty) = self.cache.get(&(self.binder_index, t)) { + if let CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { + is_hir_typeck_root_goal: true, + }) = self.canonicalize_mode + { + // If we're canonicalizing a root goal during HIR typeck, we + // must not use the `cache` as we want to map each occurrence + // of a region to a unique existential variable. + self.inner_fold_ty(t) + } else if let Some(&ty) = self.cache.get(&(self.binder_index, t)) { ty } else { - let res = self.cached_fold_ty(t); + let res = self.inner_fold_ty(t); let old = self.cache.insert((self.binder_index, t), res); assert_eq!(old, None); res @@ -541,9 +571,9 @@ impl, I: Interner> TypeFolder for Canonicaliz fn fold_clauses(&mut self, c: I::Clauses) -> I::Clauses { match self.canonicalize_mode { - CanonicalizeMode::Input { keep_static: true } + CanonicalizeMode::Input(CanonicalizeInputKind::ParamEnv) | CanonicalizeMode::Response { max_input_universe: _ } => {} - CanonicalizeMode::Input { keep_static: false } => { + CanonicalizeMode::Input(CanonicalizeInputKind::Predicate { .. }) => { panic!("erasing 'static in env") } } diff --git a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs index 5ed316aa6b1..de1330ca82a 100644 --- a/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs +++ b/compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs @@ -55,6 +55,7 @@ where /// for each bound variable. pub(super) fn canonicalize_goal( &self, + is_hir_typeck_root_goal: bool, goal: Goal, ) -> (Vec, CanonicalInput) { // We only care about one entry per `OpaqueTypeKey` here, @@ -67,6 +68,7 @@ where let canonical = Canonicalizer::canonicalize_input( self.delegate, &mut orig_values, + is_hir_typeck_root_goal, QueryInput { goal, predefined_opaques_in_body: self 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 ce9b794d40d..053ccf285cf 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 @@ -447,7 +447,10 @@ where )); } - let (orig_values, canonical_goal) = self.canonicalize_goal(goal); + let is_hir_typeck_root_goal = matches!(goal_evaluation_kind, GoalEvaluationKind::Root) + && self.delegate.in_hir_typeck(); + + let (orig_values, canonical_goal) = self.canonicalize_goal(is_hir_typeck_root_goal, goal); let mut goal_evaluation = self.inspect.new_goal_evaluation(goal, &orig_values, goal_evaluation_kind); let canonical_result = self.search_graph.evaluate_goal( diff --git a/compiler/rustc_next_trait_solver/src/solve/mod.rs b/compiler/rustc_next_trait_solver/src/solve/mod.rs index 5ea3f0d1061..f39426c7689 100644 --- a/compiler/rustc_next_trait_solver/src/solve/mod.rs +++ b/compiler/rustc_next_trait_solver/src/solve/mod.rs @@ -252,8 +252,6 @@ where return None; } - // FIXME(-Znext-solver): Add support to merge region constraints in - // responses to deal with trait-system-refactor-initiative#27. let one = responses[0]; if responses[1..].iter().all(|&resp| resp == one) { return Some(one); diff --git a/compiler/rustc_type_ir/src/infer_ctxt.rs b/compiler/rustc_type_ir/src/infer_ctxt.rs index e86a2305e23..b4873c8c71c 100644 --- a/compiler/rustc_type_ir/src/infer_ctxt.rs +++ b/compiler/rustc_type_ir/src/infer_ctxt.rs @@ -148,6 +148,10 @@ pub trait InferCtxtLike: Sized { true } + fn in_hir_typeck(&self) -> bool { + false + } + fn typing_mode(&self) -> TypingMode; fn universe(&self) -> ty::UniverseIndex; -- cgit 1.4.1-3-g733a5