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Diffstat (limited to 'compiler/rustc_infer/src/infer/canonical/query_response.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/canonical/query_response.rs | 741 |
1 files changed, 741 insertions, 0 deletions
diff --git a/compiler/rustc_infer/src/infer/canonical/query_response.rs b/compiler/rustc_infer/src/infer/canonical/query_response.rs new file mode 100644 index 000000000..8dc20544f --- /dev/null +++ b/compiler/rustc_infer/src/infer/canonical/query_response.rs @@ -0,0 +1,741 @@ +//! This module contains the code to instantiate a "query result", and +//! in particular to extract out the resulting region obligations and +//! encode them therein. +//! +//! For an overview of what canonicalization is and how it fits into +//! rustc, check out the [chapter in the rustc dev guide][c]. +//! +//! [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html + +use crate::infer::canonical::substitute::{substitute_value, CanonicalExt}; +use crate::infer::canonical::{ + Canonical, CanonicalVarValues, CanonicalizedQueryResponse, Certainty, OriginalQueryValues, + QueryOutlivesConstraint, QueryRegionConstraints, QueryResponse, +}; +use crate::infer::nll_relate::{NormalizationStrategy, TypeRelating, TypeRelatingDelegate}; +use crate::infer::region_constraints::{Constraint, RegionConstraintData}; +use crate::infer::{InferCtxt, InferOk, InferResult, NllRegionVariableOrigin}; +use crate::traits::query::{Fallible, NoSolution}; +use crate::traits::TraitEngine; +use crate::traits::{Obligation, ObligationCause, PredicateObligation}; +use rustc_data_structures::captures::Captures; +use rustc_index::vec::Idx; +use rustc_index::vec::IndexVec; +use rustc_middle::arena::ArenaAllocatable; +use rustc_middle::ty::error::TypeError; +use rustc_middle::ty::fold::TypeFoldable; +use rustc_middle::ty::relate::TypeRelation; +use rustc_middle::ty::subst::{GenericArg, GenericArgKind}; +use rustc_middle::ty::{self, BoundVar, Const, ToPredicate, Ty, TyCtxt}; +use rustc_span::Span; +use std::fmt::Debug; +use std::iter; + +impl<'cx, 'tcx> InferCtxt<'cx, 'tcx> { + /// This method is meant to be invoked as the final step of a canonical query + /// implementation. It is given: + /// + /// - the instantiated variables `inference_vars` created from the query key + /// - the result `answer` of the query + /// - a fulfillment context `fulfill_cx` that may contain various obligations which + /// have yet to be proven. + /// + /// Given this, the function will process the obligations pending + /// in `fulfill_cx`: + /// + /// - If all the obligations can be proven successfully, it will + /// package up any resulting region obligations (extracted from + /// `infcx`) along with the fully resolved value `answer` into a + /// query result (which is then itself canonicalized). + /// - If some obligations can be neither proven nor disproven, then + /// the same thing happens, but the resulting query is marked as ambiguous. + /// - Finally, if any of the obligations result in a hard error, + /// then `Err(NoSolution)` is returned. + #[instrument(skip(self, inference_vars, answer, fulfill_cx), level = "trace")] + pub fn make_canonicalized_query_response<T>( + &self, + inference_vars: CanonicalVarValues<'tcx>, + answer: T, + fulfill_cx: &mut dyn TraitEngine<'tcx>, + ) -> Fallible<CanonicalizedQueryResponse<'tcx, T>> + where + T: Debug + TypeFoldable<'tcx>, + Canonical<'tcx, QueryResponse<'tcx, T>>: ArenaAllocatable<'tcx>, + { + let query_response = self.make_query_response(inference_vars, answer, fulfill_cx)?; + let canonical_result = self.canonicalize_response(query_response); + + debug!("canonical_result = {:#?}", canonical_result); + + Ok(self.tcx.arena.alloc(canonical_result)) + } + + /// A version of `make_canonicalized_query_response` that does + /// not pack in obligations, for contexts that want to drop + /// pending obligations instead of treating them as an ambiguity (e.g. + /// typeck "probing" contexts). + /// + /// If you DO want to keep track of pending obligations (which + /// include all region obligations, so this includes all cases + /// that care about regions) with this function, you have to + /// do it yourself, by e.g., having them be a part of the answer. + pub fn make_query_response_ignoring_pending_obligations<T>( + &self, + inference_vars: CanonicalVarValues<'tcx>, + answer: T, + ) -> Canonical<'tcx, QueryResponse<'tcx, T>> + where + T: Debug + TypeFoldable<'tcx>, + { + self.canonicalize_response(QueryResponse { + var_values: inference_vars, + region_constraints: QueryRegionConstraints::default(), + certainty: Certainty::Proven, // Ambiguities are OK! + opaque_types: vec![], + value: answer, + }) + } + + /// Helper for `make_canonicalized_query_response` that does + /// everything up until the final canonicalization. + #[instrument(skip(self, fulfill_cx), level = "debug")] + fn make_query_response<T>( + &self, + inference_vars: CanonicalVarValues<'tcx>, + answer: T, + fulfill_cx: &mut dyn TraitEngine<'tcx>, + ) -> Result<QueryResponse<'tcx, T>, NoSolution> + where + T: Debug + TypeFoldable<'tcx>, + { + let tcx = self.tcx; + + // Select everything, returning errors. + let true_errors = fulfill_cx.select_where_possible(self); + debug!("true_errors = {:#?}", true_errors); + + if !true_errors.is_empty() { + // FIXME -- we don't indicate *why* we failed to solve + debug!("make_query_response: true_errors={:#?}", true_errors); + return Err(NoSolution); + } + + // Anything left unselected *now* must be an ambiguity. + let ambig_errors = fulfill_cx.select_all_or_error(self); + debug!("ambig_errors = {:#?}", ambig_errors); + + let region_obligations = self.take_registered_region_obligations(); + let region_constraints = self.with_region_constraints(|region_constraints| { + make_query_region_constraints( + tcx, + region_obligations.iter().map(|r_o| (r_o.sup_type, r_o.sub_region)), + region_constraints, + ) + }); + + let certainty = + if ambig_errors.is_empty() { Certainty::Proven } else { Certainty::Ambiguous }; + + let opaque_types = self.take_opaque_types_for_query_response(); + + Ok(QueryResponse { + var_values: inference_vars, + region_constraints, + certainty, + value: answer, + opaque_types, + }) + } + + fn take_opaque_types_for_query_response(&self) -> Vec<(Ty<'tcx>, Ty<'tcx>)> { + self.inner + .borrow_mut() + .opaque_type_storage + .take_opaque_types() + .into_iter() + .map(|(k, v)| (self.tcx.mk_opaque(k.def_id.to_def_id(), k.substs), v.hidden_type.ty)) + .collect() + } + + /// Given the (canonicalized) result to a canonical query, + /// instantiates the result so it can be used, plugging in the + /// values from the canonical query. (Note that the result may + /// have been ambiguous; you should check the certainty level of + /// the query before applying this function.) + /// + /// To get a good understanding of what is happening here, check + /// out the [chapter in the rustc dev guide][c]. + /// + /// [c]: https://rust-lang.github.io/chalk/book/canonical_queries/canonicalization.html#processing-the-canonicalized-query-result + pub fn instantiate_query_response_and_region_obligations<R>( + &self, + cause: &ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + original_values: &OriginalQueryValues<'tcx>, + query_response: &Canonical<'tcx, QueryResponse<'tcx, R>>, + ) -> InferResult<'tcx, R> + where + R: Debug + TypeFoldable<'tcx>, + { + let InferOk { value: result_subst, mut obligations } = + self.query_response_substitution(cause, param_env, original_values, query_response)?; + + obligations.extend(self.query_outlives_constraints_into_obligations( + cause, + param_env, + &query_response.value.region_constraints.outlives, + &result_subst, + )); + + let user_result: R = + query_response.substitute_projected(self.tcx, &result_subst, |q_r| q_r.value.clone()); + + Ok(InferOk { value: user_result, obligations }) + } + + /// An alternative to + /// `instantiate_query_response_and_region_obligations` that is more + /// efficient for NLL. NLL is a bit more advanced in the + /// "transition to chalk" than the rest of the compiler. During + /// the NLL type check, all of the "processing" of types and + /// things happens in queries -- the NLL checker itself is only + /// interested in the region obligations (`'a: 'b` or `T: 'b`) + /// that come out of these queries, which it wants to convert into + /// MIR-based constraints and solve. Therefore, it is most + /// convenient for the NLL Type Checker to **directly consume** + /// the `QueryOutlivesConstraint` values that arise from doing a + /// query. This is contrast to other parts of the compiler, which + /// would prefer for those `QueryOutlivesConstraint` to be converted + /// into the older infcx-style constraints (e.g., calls to + /// `sub_regions` or `register_region_obligation`). + /// + /// Therefore, `instantiate_nll_query_response_and_region_obligations` performs the same + /// basic operations as `instantiate_query_response_and_region_obligations` but + /// it returns its result differently: + /// + /// - It creates a substitution `S` that maps from the original + /// query variables to the values computed in the query + /// result. If any errors arise, they are propagated back as an + /// `Err` result. + /// - In the case of a successful substitution, we will append + /// `QueryOutlivesConstraint` values onto the + /// `output_query_region_constraints` vector for the solver to + /// use (if an error arises, some values may also be pushed, but + /// they should be ignored). + /// - It **can happen** (though it rarely does currently) that + /// equating types and things will give rise to subobligations + /// that must be processed. In this case, those subobligations + /// are propagated back in the return value. + /// - Finally, the query result (of type `R`) is propagated back, + /// after applying the substitution `S`. + pub fn instantiate_nll_query_response_and_region_obligations<R>( + &self, + cause: &ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + original_values: &OriginalQueryValues<'tcx>, + query_response: &Canonical<'tcx, QueryResponse<'tcx, R>>, + output_query_region_constraints: &mut QueryRegionConstraints<'tcx>, + ) -> InferResult<'tcx, R> + where + R: Debug + TypeFoldable<'tcx>, + { + let InferOk { value: result_subst, mut obligations } = self + .query_response_substitution_guess(cause, param_env, original_values, query_response)?; + + // Compute `QueryOutlivesConstraint` values that unify each of + // the original values `v_o` that was canonicalized into a + // variable... + + for (index, original_value) in original_values.var_values.iter().enumerate() { + // ...with the value `v_r` of that variable from the query. + let result_value = query_response.substitute_projected(self.tcx, &result_subst, |v| { + v.var_values[BoundVar::new(index)] + }); + match (original_value.unpack(), result_value.unpack()) { + (GenericArgKind::Lifetime(re1), GenericArgKind::Lifetime(re2)) + if re1.is_erased() && re2.is_erased() => + { + // No action needed. + } + + (GenericArgKind::Lifetime(v_o), GenericArgKind::Lifetime(v_r)) => { + // To make `v_o = v_r`, we emit `v_o: v_r` and `v_r: v_o`. + if v_o != v_r { + output_query_region_constraints + .outlives + .push(ty::Binder::dummy(ty::OutlivesPredicate(v_o.into(), v_r))); + output_query_region_constraints + .outlives + .push(ty::Binder::dummy(ty::OutlivesPredicate(v_r.into(), v_o))); + } + } + + (GenericArgKind::Type(v1), GenericArgKind::Type(v2)) => { + TypeRelating::new( + self, + QueryTypeRelatingDelegate { + infcx: self, + param_env, + cause, + obligations: &mut obligations, + }, + ty::Variance::Invariant, + ) + .relate(v1, v2)?; + } + + (GenericArgKind::Const(v1), GenericArgKind::Const(v2)) => { + TypeRelating::new( + self, + QueryTypeRelatingDelegate { + infcx: self, + param_env, + cause, + obligations: &mut obligations, + }, + ty::Variance::Invariant, + ) + .relate(v1, v2)?; + } + + _ => { + bug!("kind mismatch, cannot unify {:?} and {:?}", original_value, result_value); + } + } + } + + // ...also include the other query region constraints from the query. + output_query_region_constraints.outlives.extend( + query_response.value.region_constraints.outlives.iter().filter_map(|&r_c| { + let r_c = substitute_value(self.tcx, &result_subst, r_c); + + // Screen out `'a: 'a` cases -- we skip the binder here but + // only compare the inner values to one another, so they are still at + // consistent binding levels. + let ty::OutlivesPredicate(k1, r2) = r_c.skip_binder(); + if k1 != r2.into() { Some(r_c) } else { None } + }), + ); + + // ...also include the query member constraints. + output_query_region_constraints.member_constraints.extend( + query_response + .value + .region_constraints + .member_constraints + .iter() + .map(|p_c| substitute_value(self.tcx, &result_subst, p_c.clone())), + ); + + let user_result: R = + query_response.substitute_projected(self.tcx, &result_subst, |q_r| q_r.value.clone()); + + Ok(InferOk { value: user_result, obligations }) + } + + /// Given the original values and the (canonicalized) result from + /// computing a query, returns a substitution that can be applied + /// to the query result to convert the result back into the + /// original namespace. + /// + /// The substitution also comes accompanied with subobligations + /// that arose from unification; these might occur if (for + /// example) we are doing lazy normalization and the value + /// assigned to a type variable is unified with an unnormalized + /// projection. + fn query_response_substitution<R>( + &self, + cause: &ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + original_values: &OriginalQueryValues<'tcx>, + query_response: &Canonical<'tcx, QueryResponse<'tcx, R>>, + ) -> InferResult<'tcx, CanonicalVarValues<'tcx>> + where + R: Debug + TypeFoldable<'tcx>, + { + debug!( + "query_response_substitution(original_values={:#?}, query_response={:#?})", + original_values, query_response, + ); + + let mut value = self.query_response_substitution_guess( + cause, + param_env, + original_values, + query_response, + )?; + + value.obligations.extend( + self.unify_query_response_substitution_guess( + cause, + param_env, + original_values, + &value.value, + query_response, + )? + .into_obligations(), + ); + + Ok(value) + } + + /// Given the original values and the (canonicalized) result from + /// computing a query, returns a **guess** at a substitution that + /// can be applied to the query result to convert the result back + /// into the original namespace. This is called a **guess** + /// because it uses a quick heuristic to find the values for each + /// canonical variable; if that quick heuristic fails, then we + /// will instantiate fresh inference variables for each canonical + /// variable instead. Therefore, the result of this method must be + /// properly unified + fn query_response_substitution_guess<R>( + &self, + cause: &ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + original_values: &OriginalQueryValues<'tcx>, + query_response: &Canonical<'tcx, QueryResponse<'tcx, R>>, + ) -> InferResult<'tcx, CanonicalVarValues<'tcx>> + where + R: Debug + TypeFoldable<'tcx>, + { + debug!( + "query_response_substitution_guess(original_values={:#?}, query_response={:#?})", + original_values, query_response, + ); + + // For each new universe created in the query result that did + // not appear in the original query, create a local + // superuniverse. + let mut universe_map = original_values.universe_map.clone(); + let num_universes_in_query = original_values.universe_map.len(); + let num_universes_in_response = query_response.max_universe.as_usize() + 1; + for _ in num_universes_in_query..num_universes_in_response { + universe_map.push(self.create_next_universe()); + } + assert!(!universe_map.is_empty()); // always have the root universe + assert_eq!(universe_map[ty::UniverseIndex::ROOT.as_usize()], ty::UniverseIndex::ROOT); + + // Every canonical query result includes values for each of + // the inputs to the query. Therefore, we begin by unifying + // these values with the original inputs that were + // canonicalized. + let result_values = &query_response.value.var_values; + assert_eq!(original_values.var_values.len(), result_values.len()); + + // Quickly try to find initial values for the canonical + // variables in the result in terms of the query. We do this + // by iterating down the values that the query gave to each of + // the canonical inputs. If we find that one of those values + // is directly equal to one of the canonical variables in the + // result, then we can type the corresponding value from the + // input. See the example above. + let mut opt_values: IndexVec<BoundVar, Option<GenericArg<'tcx>>> = + IndexVec::from_elem_n(None, query_response.variables.len()); + + // In terms of our example above, we are iterating over pairs like: + // [(?A, Vec<?0>), ('static, '?1), (?B, ?0)] + for (original_value, result_value) in iter::zip(&original_values.var_values, result_values) + { + match result_value.unpack() { + GenericArgKind::Type(result_value) => { + // e.g., here `result_value` might be `?0` in the example above... + if let ty::Bound(debruijn, b) = *result_value.kind() { + // ...in which case we would set `canonical_vars[0]` to `Some(?U)`. + + // We only allow a `ty::INNERMOST` index in substitutions. + assert_eq!(debruijn, ty::INNERMOST); + opt_values[b.var] = Some(*original_value); + } + } + GenericArgKind::Lifetime(result_value) => { + // e.g., here `result_value` might be `'?1` in the example above... + if let ty::ReLateBound(debruijn, br) = *result_value { + // ... in which case we would set `canonical_vars[0]` to `Some('static)`. + + // We only allow a `ty::INNERMOST` index in substitutions. + assert_eq!(debruijn, ty::INNERMOST); + opt_values[br.var] = Some(*original_value); + } + } + GenericArgKind::Const(result_value) => { + if let ty::ConstKind::Bound(debrujin, b) = result_value.kind() { + // ...in which case we would set `canonical_vars[0]` to `Some(const X)`. + + // We only allow a `ty::INNERMOST` index in substitutions. + assert_eq!(debrujin, ty::INNERMOST); + opt_values[b] = Some(*original_value); + } + } + } + } + + // Create a result substitution: if we found a value for a + // given variable in the loop above, use that. Otherwise, use + // a fresh inference variable. + let result_subst = CanonicalVarValues { + var_values: query_response + .variables + .iter() + .enumerate() + .map(|(index, info)| { + if info.is_existential() { + match opt_values[BoundVar::new(index)] { + Some(k) => k, + None => self.instantiate_canonical_var(cause.span, info, |u| { + universe_map[u.as_usize()] + }), + } + } else { + self.instantiate_canonical_var(cause.span, info, |u| { + universe_map[u.as_usize()] + }) + } + }) + .collect(), + }; + + let mut obligations = vec![]; + + // Carry all newly resolved opaque types to the caller's scope + for &(a, b) in &query_response.value.opaque_types { + let a = substitute_value(self.tcx, &result_subst, a); + let b = substitute_value(self.tcx, &result_subst, b); + obligations.extend(self.handle_opaque_type(a, b, true, cause, param_env)?.obligations); + } + + Ok(InferOk { value: result_subst, obligations }) + } + + /// Given a "guess" at the values for the canonical variables in + /// the input, try to unify with the *actual* values found in the + /// query result. Often, but not always, this is a no-op, because + /// we already found the mapping in the "guessing" step. + /// + /// See also: `query_response_substitution_guess` + fn unify_query_response_substitution_guess<R>( + &self, + cause: &ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + original_values: &OriginalQueryValues<'tcx>, + result_subst: &CanonicalVarValues<'tcx>, + query_response: &Canonical<'tcx, QueryResponse<'tcx, R>>, + ) -> InferResult<'tcx, ()> + where + R: Debug + TypeFoldable<'tcx>, + { + // A closure that yields the result value for the given + // canonical variable; this is taken from + // `query_response.var_values` after applying the substitution + // `result_subst`. + let substituted_query_response = |index: BoundVar| -> GenericArg<'tcx> { + query_response.substitute_projected(self.tcx, &result_subst, |v| v.var_values[index]) + }; + + // Unify the original value for each variable with the value + // taken from `query_response` (after applying `result_subst`). + self.unify_canonical_vars(cause, param_env, original_values, substituted_query_response) + } + + /// Converts the region constraints resulting from a query into an + /// iterator of obligations. + fn query_outlives_constraints_into_obligations<'a>( + &'a self, + cause: &'a ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + unsubstituted_region_constraints: &'a [QueryOutlivesConstraint<'tcx>], + result_subst: &'a CanonicalVarValues<'tcx>, + ) -> impl Iterator<Item = PredicateObligation<'tcx>> + 'a + Captures<'tcx> { + unsubstituted_region_constraints.iter().map(move |&constraint| { + let predicate = substitute_value(self.tcx, result_subst, constraint); + self.query_outlives_constraint_to_obligation(predicate, cause.clone(), param_env) + }) + } + + pub fn query_outlives_constraint_to_obligation( + &self, + predicate: QueryOutlivesConstraint<'tcx>, + cause: ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + ) -> Obligation<'tcx, ty::Predicate<'tcx>> { + let ty::OutlivesPredicate(k1, r2) = predicate.skip_binder(); + + let atom = match k1.unpack() { + GenericArgKind::Lifetime(r1) => { + ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate(r1, r2)) + } + GenericArgKind::Type(t1) => { + ty::PredicateKind::TypeOutlives(ty::OutlivesPredicate(t1, r2)) + } + GenericArgKind::Const(..) => { + // Consts cannot outlive one another, so we don't expect to + // encounter this branch. + span_bug!(cause.span, "unexpected const outlives {:?}", predicate); + } + }; + let predicate = predicate.rebind(atom).to_predicate(self.tcx); + + Obligation::new(cause, param_env, predicate) + } + + /// Given two sets of values for the same set of canonical variables, unify them. + /// The second set is produced lazily by supplying indices from the first set. + fn unify_canonical_vars( + &self, + cause: &ObligationCause<'tcx>, + param_env: ty::ParamEnv<'tcx>, + variables1: &OriginalQueryValues<'tcx>, + variables2: impl Fn(BoundVar) -> GenericArg<'tcx>, + ) -> InferResult<'tcx, ()> { + self.commit_if_ok(|_| { + let mut obligations = vec![]; + for (index, value1) in variables1.var_values.iter().enumerate() { + let value2 = variables2(BoundVar::new(index)); + + match (value1.unpack(), value2.unpack()) { + (GenericArgKind::Type(v1), GenericArgKind::Type(v2)) => { + obligations + .extend(self.at(cause, param_env).eq(v1, v2)?.into_obligations()); + } + (GenericArgKind::Lifetime(re1), GenericArgKind::Lifetime(re2)) + if re1.is_erased() && re2.is_erased() => + { + // no action needed + } + (GenericArgKind::Lifetime(v1), GenericArgKind::Lifetime(v2)) => { + obligations + .extend(self.at(cause, param_env).eq(v1, v2)?.into_obligations()); + } + (GenericArgKind::Const(v1), GenericArgKind::Const(v2)) => { + let ok = self.at(cause, param_env).eq(v1, v2)?; + obligations.extend(ok.into_obligations()); + } + _ => { + bug!("kind mismatch, cannot unify {:?} and {:?}", value1, value2,); + } + } + } + Ok(InferOk { value: (), obligations }) + }) + } +} + +/// Given the region obligations and constraints scraped from the infcx, +/// creates query region constraints. +pub fn make_query_region_constraints<'tcx>( + tcx: TyCtxt<'tcx>, + outlives_obligations: impl Iterator<Item = (Ty<'tcx>, ty::Region<'tcx>)>, + region_constraints: &RegionConstraintData<'tcx>, +) -> QueryRegionConstraints<'tcx> { + let RegionConstraintData { constraints, verifys, givens, member_constraints } = + region_constraints; + + assert!(verifys.is_empty()); + assert!(givens.is_empty()); + + let outlives: Vec<_> = constraints + .iter() + .map(|(k, _)| match *k { + // Swap regions because we are going from sub (<=) to outlives + // (>=). + Constraint::VarSubVar(v1, v2) => ty::OutlivesPredicate( + tcx.mk_region(ty::ReVar(v2)).into(), + tcx.mk_region(ty::ReVar(v1)), + ), + Constraint::VarSubReg(v1, r2) => { + ty::OutlivesPredicate(r2.into(), tcx.mk_region(ty::ReVar(v1))) + } + Constraint::RegSubVar(r1, v2) => { + ty::OutlivesPredicate(tcx.mk_region(ty::ReVar(v2)).into(), r1) + } + Constraint::RegSubReg(r1, r2) => ty::OutlivesPredicate(r2.into(), r1), + }) + .map(ty::Binder::dummy) // no bound vars in the code above + .chain( + outlives_obligations + .map(|(ty, r)| ty::OutlivesPredicate(ty.into(), r)) + .map(ty::Binder::dummy), // no bound vars in the code above + ) + .collect(); + + QueryRegionConstraints { outlives, member_constraints: member_constraints.clone() } +} + +struct QueryTypeRelatingDelegate<'a, 'tcx> { + infcx: &'a InferCtxt<'a, 'tcx>, + obligations: &'a mut Vec<PredicateObligation<'tcx>>, + param_env: ty::ParamEnv<'tcx>, + cause: &'a ObligationCause<'tcx>, +} + +impl<'tcx> TypeRelatingDelegate<'tcx> for QueryTypeRelatingDelegate<'_, 'tcx> { + fn span(&self) -> Span { + self.cause.span + } + + fn param_env(&self) -> ty::ParamEnv<'tcx> { + self.param_env + } + + fn create_next_universe(&mut self) -> ty::UniverseIndex { + self.infcx.create_next_universe() + } + + fn next_existential_region_var(&mut self, from_forall: bool) -> ty::Region<'tcx> { + let origin = NllRegionVariableOrigin::Existential { from_forall }; + self.infcx.next_nll_region_var(origin) + } + + fn next_placeholder_region(&mut self, placeholder: ty::PlaceholderRegion) -> ty::Region<'tcx> { + self.infcx.tcx.mk_region(ty::RePlaceholder(placeholder)) + } + + fn generalize_existential(&mut self, universe: ty::UniverseIndex) -> ty::Region<'tcx> { + self.infcx.next_nll_region_var_in_universe( + NllRegionVariableOrigin::Existential { from_forall: false }, + universe, + ) + } + + fn push_outlives( + &mut self, + sup: ty::Region<'tcx>, + sub: ty::Region<'tcx>, + _info: ty::VarianceDiagInfo<'tcx>, + ) { + self.obligations.push(Obligation { + cause: self.cause.clone(), + param_env: self.param_env, + predicate: ty::Binder::dummy(ty::PredicateKind::RegionOutlives(ty::OutlivesPredicate( + sup, sub, + ))) + .to_predicate(self.infcx.tcx), + recursion_depth: 0, + }); + } + + fn const_equate(&mut self, _a: Const<'tcx>, _b: Const<'tcx>) { + span_bug!(self.cause.span(), "generic_const_exprs: unreachable `const_equate`"); + } + + fn normalization() -> NormalizationStrategy { + NormalizationStrategy::Eager + } + + fn forbid_inference_vars() -> bool { + true + } + + fn register_opaque_type( + &mut self, + a: Ty<'tcx>, + b: Ty<'tcx>, + a_is_expected: bool, + ) -> Result<(), TypeError<'tcx>> { + self.obligations.extend( + self.infcx + .handle_opaque_type(a, b, a_is_expected, &self.cause, self.param_env)? + .obligations, + ); + Ok(()) + } +} |