diff options
Diffstat (limited to 'compiler')
| -rw-r--r-- | compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs | 163 |
1 files changed, 1 insertions, 162 deletions
diff --git a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs index bae6103cad5..d7e1b4545b8 100644 --- a/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs +++ b/compiler/rustc_infer/src/infer/lexical_region_resolve/mod.rs @@ -2,7 +2,6 @@ use crate::infer::region_constraints::Constraint; use crate::infer::region_constraints::GenericKind; -use crate::infer::region_constraints::MemberConstraint; use crate::infer::region_constraints::RegionConstraintData; use crate::infer::region_constraints::VarInfos; use crate::infer::region_constraints::VerifyBound; @@ -150,12 +149,7 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> { let graph = self.construct_graph(); self.expand_givens(&graph); - loop { - self.expansion(&mut var_data); - if !self.enforce_member_constraints(&graph, &mut var_data) { - break; - } - } + self.expansion(&mut var_data); self.collect_errors(&mut var_data, errors); self.collect_var_errors(&var_data, &graph, errors); var_data @@ -233,133 +227,6 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> { } } - /// Enforce all member constraints and return true if anything - /// changed. See `enforce_member_constraint` for more details. - fn enforce_member_constraints( - &self, - graph: &RegionGraph<'tcx>, - var_values: &mut LexicalRegionResolutions<'tcx>, - ) -> bool { - // Note: we don't use the `any` combinator because we don't - // want to stop at the first constraint that makes a change. - let mut any_changed = false; - for member_constraint in &self.data.member_constraints { - any_changed |= self.enforce_member_constraint(graph, member_constraint, var_values); - } - any_changed - } - - /// Enforce a constraint like - /// - /// ``` - /// 'r member of ['c...] - /// ``` - /// - /// We look for all choice regions from the list `'c...` that: - /// - /// (a) are greater than the current value of `'r` (which is a lower bound) - /// - /// and - /// - /// (b) are compatible with the upper bounds of `'r` that we can - /// find by traversing the graph. - /// - /// From that list, we look for a *minimal* option `'c_min`. If we - /// find one, then we can enforce that `'r: 'c_min`. - #[instrument(level = "debug", skip(self, graph, member_constraint, var_values))] - fn enforce_member_constraint( - &self, - graph: &RegionGraph<'tcx>, - member_constraint: &MemberConstraint<'tcx>, - var_values: &mut LexicalRegionResolutions<'tcx>, - ) -> bool { - debug!("member_constraint={:#?}", member_constraint); - - // The constraint is some inference variable (`vid`) which - // must be equal to one of the options. - let member_vid = match member_constraint.member_region { - ty::ReVar(vid) => *vid, - _ => return false, - }; - - // The current value of `vid` is a lower bound LB -- i.e., we - // know that `LB <= vid` must be true. - let member_lower_bound: ty::Region<'tcx> = match var_values.value(member_vid) { - VarValue::ErrorValue => return false, - VarValue::Value(r) => r, - }; - - // Find all the "upper bounds" -- that is, each region `b` such that - // `r0 <= b` must hold. - let (member_upper_bounds, ..) = - self.collect_bounding_regions(graph, member_vid, OUTGOING, None); - - // Get an iterator over the *available choice* -- that is, - // each choice region `c` where `lb <= c` and `c <= ub` for all the - // upper bounds `ub`. - debug!("upper_bounds={:#?}", member_upper_bounds); - let mut options = member_constraint - .choice_regions - .iter() - // If any of the regions are inference vars, resolve them, as far - // as possible. - .filter_map(|option| match option { - ty::ReVar(vid) => match var_values.value(*vid) { - VarValue::ErrorValue => None, - VarValue::Value(r) => Some(r), - }, - r => Some(r), - }) - .filter(|option| { - self.sub_concrete_regions(member_lower_bound, option) - && member_upper_bounds - .iter() - .all(|upper_bound| self.sub_concrete_regions(option, upper_bound.region)) - }); - - // If there is more than one option, we only make a choice if - // there is a single *least* choice -- i.e., some available - // region that is `<=` all the others. - let mut least_choice: ty::Region<'tcx> = match options.next() { - Some(&r) => r, - None => return false, - }; - debug!(?least_choice); - for &option in options { - debug!(?option); - if !self.sub_concrete_regions(least_choice, option) { - if self.sub_concrete_regions(option, least_choice) { - debug!("new least choice"); - least_choice = option; - } else { - debug!("no least choice"); - return false; - } - } - } - - // (#72087) Different `ty::Regions` can be known to be equal, for - // example, we know that `'a` and `'static` are equal in a function - // with a parameter of type `&'static &'a ()`. - // - // When we have two equal regions like this `expansion` will use - // `lub_concrete_regions` to pick a canonical representative. The same - // choice is needed here so that we don't end up in a cycle of - // `expansion` changing the region one way and the code here changing - // it back. - let lub = self.lub_concrete_regions(least_choice, member_lower_bound); - debug!( - "enforce_member_constraint: final least choice = {:?}\nlub = {:?}", - least_choice, lub - ); - if lub != member_lower_bound { - *var_values.value_mut(member_vid) = VarValue::Value(least_choice); - true - } else { - false - } - } - fn expansion(&self, var_values: &mut LexicalRegionResolutions<'tcx>) { let mut constraints = IndexVec::from_elem_n(Vec::new(), var_values.values.len()); let mut changes = Vec::new(); @@ -632,34 +499,6 @@ impl<'cx, 'tcx> LexicalResolver<'cx, 'tcx> { } } - // Check that all member constraints are satisfied. - for member_constraint in &self.data.member_constraints { - let member_region = var_data.normalize(self.tcx(), member_constraint.member_region); - let choice_regions = member_constraint - .choice_regions - .iter() - .map(|&choice_region| var_data.normalize(self.tcx(), choice_region)); - let fr = &self.region_rels.free_regions; - let sub = |a, b| { - fr.is_free_or_static(a) - && fr.is_free_or_static(b) - && fr.sub_free_regions(self.tcx(), a, b) - }; - if !choice_regions.clone().any(|choice_region| { - // This is really checking if the regions are equal. After member constraint - // resolution, one region must be equal, or a lifetime has been leaked into - // the hidden type, but does not appear in the corresponding impl trait. - sub(member_region, choice_region) && sub(choice_region, member_region) - }) { - let span = self.tcx().def_span(member_constraint.opaque_type_def_id); - errors.push(RegionResolutionError::MemberConstraintFailure { - span, - hidden_ty: member_constraint.hidden_ty, - member_region, - }); - } - } - for verify in &self.data.verifys { debug!("collect_errors: verify={:?}", verify); let sub = var_data.normalize(self.tcx(), verify.region); |