Expand weak alias types before collecting constrained/referenced late bound regions + refactorings

compiler/rustc_hir_analysis/src/astconv/bounds.rs

@@ -454,9 +454,9 @@ impl<'tcx> dyn AstConv<'tcx> + '_ {
                     //     for<'a> <T as Iterator>::Item = &'a str // <-- 'a is bad
                     //     for<'a> <T as FnMut<(&'a u32,)>>::Output = &'a str // <-- 'a is ok
                     let late_bound_in_projection_ty =
-                        tcx.collect_constrained_late_bound_regions(&projection_ty);
+                        tcx.collect_constrained_late_bound_regions(projection_ty);
                     let late_bound_in_term =
-                        tcx.collect_referenced_late_bound_regions(&trait_ref.rebind(term));
+                        tcx.collect_referenced_late_bound_regions(trait_ref.rebind(term));
                     debug!(?late_bound_in_projection_ty);
                     debug!(?late_bound_in_term);
 

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -2678,9 +2678,9 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         //     for<'a> fn(&'a String) -> &'a str <-- 'a is ok
         let inputs = bare_fn_ty.inputs();
         let late_bound_in_args =
-            tcx.collect_constrained_late_bound_regions(&inputs.map_bound(|i| i.to_owned()));
+            tcx.collect_constrained_late_bound_regions(inputs.map_bound(|i| i.to_owned()));
         let output = bare_fn_ty.output();
-        let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(&output);
+        let late_bound_in_ret = tcx.collect_referenced_late_bound_regions(output);
 
         self.validate_late_bound_regions(late_bound_in_args, late_bound_in_ret, |br_name| {
             struct_span_code_err!(

compiler/rustc_hir_analysis/src/coherence/inherent_impls.rs

@@ -144,7 +144,7 @@ impl<'tcx> InherentCollect<'tcx> {
         let id = id.owner_id.def_id;
         let item_span = self.tcx.def_span(id);
         let self_ty = self.tcx.type_of(id).instantiate_identity();
-        let self_ty = peel_off_weak_aliases(self.tcx, self_ty);
+        let self_ty = self.tcx.peel_off_weak_alias_tys(self_ty);
         match *self_ty.kind() {
             ty::Adt(def, _) => self.check_def_id(id, self_ty, def.did()),
             ty::Foreign(did) => self.check_def_id(id, self_ty, did),
@@ -186,30 +186,3 @@ impl<'tcx> InherentCollect<'tcx> {
         }
     }
 }
-
-/// Peel off all weak alias types in this type until there are none left.
-///
-/// <div class="warning">
-///
-/// This assumes that `ty` gets normalized later and that any overflows occurring
-/// during said normalization get reported.
-///
-/// </div>
-fn peel_off_weak_aliases<'tcx>(tcx: TyCtxt<'tcx>, mut ty: Ty<'tcx>) -> Ty<'tcx> {
-    let ty::Alias(ty::Weak, _) = ty.kind() else { return ty };
-
-    let limit = tcx.recursion_limit();
-    let mut depth = 0;
-
-    while let ty::Alias(ty::Weak, alias) = ty.kind() {
-        if !limit.value_within_limit(depth) {
-            let guar = tcx.dcx().delayed_bug("overflow expanding weak alias type");
-            return Ty::new_error(tcx, guar);
-        }
-
-        ty = tcx.type_of(alias.def_id).instantiate(tcx, alias.args);
-        depth += 1;
-    }
-
-    ty
-}

compiler/rustc_hir_analysis/src/collect.rs

@@ -520,7 +520,7 @@ fn get_new_lifetime_name<'tcx>(
     generics: &hir::Generics<'tcx>,
 ) -> String {
     let existing_lifetimes = tcx
-        .collect_referenced_late_bound_regions(&poly_trait_ref)
+        .collect_referenced_late_bound_regions(poly_trait_ref)
         .into_iter()
         .filter_map(|lt| {
             if let ty::BoundRegionKind::BrNamed(_, name) = lt {

compiler/rustc_hir_analysis/src/constrained_generic_params.rs

@@ -1,8 +1,8 @@
 use rustc_data_structures::fx::FxHashSet;
-use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitor};
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::Span;
+use rustc_type_ir::fold::TypeFoldable;
 use std::ops::ControlFlow;
 
 #[derive(Clone, PartialEq, Eq, Hash, Debug)]
@@ -33,62 +33,47 @@ pub fn parameters_for_impl<'tcx>(
     impl_trait_ref: Option<ty::TraitRef<'tcx>>,
 ) -> FxHashSet<Parameter> {
     let vec = match impl_trait_ref {
-        Some(tr) => parameters_for(tcx, &tr, false),
-        None => parameters_for(tcx, &impl_self_ty, false),
+        Some(tr) => parameters_for(tcx, tr, false),
+        None => parameters_for(tcx, impl_self_ty, false),
     };
     vec.into_iter().collect()
 }
 
 /// If `include_nonconstraining` is false, returns the list of parameters that are
-/// constrained by `t` - i.e., the value of each parameter in the list is
-/// uniquely determined by `t` (see RFC 447). If it is true, return the list
-/// of parameters whose values are needed in order to constrain `ty` - these
+/// constrained by `value` - i.e., the value of each parameter in the list is
+/// uniquely determined by `value` (see RFC 447). If it is true, return the list
+/// of parameters whose values are needed in order to constrain `value` - these
 /// differ, with the latter being a superset, in the presence of projections.
 pub fn parameters_for<'tcx>(
     tcx: TyCtxt<'tcx>,
-    t: &impl TypeVisitable<TyCtxt<'tcx>>,
+    value: impl TypeFoldable<TyCtxt<'tcx>>,
     include_nonconstraining: bool,
 ) -> Vec<Parameter> {
-    let mut collector =
-        ParameterCollector { tcx, parameters: vec![], include_nonconstraining, depth: 0 };
-    t.visit_with(&mut collector);
+    let mut collector = ParameterCollector { parameters: vec![], include_nonconstraining };
+    let value = if !include_nonconstraining { tcx.expand_weak_alias_tys(value) } else { value };
+    value.visit_with(&mut collector);
     collector.parameters
 }
 
-struct ParameterCollector<'tcx> {
-    tcx: TyCtxt<'tcx>,
+struct ParameterCollector {
     parameters: Vec<Parameter>,
     include_nonconstraining: bool,
-    depth: usize,
 }
 
-impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParameterCollector<'tcx> {
+impl<'tcx> TypeVisitor<TyCtxt<'tcx>> for ParameterCollector {
     fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
         match *t.kind() {
+            // Projections are not injective in general.
             ty::Alias(ty::Projection | ty::Inherent | ty::Opaque, _)
                 if !self.include_nonconstraining =>
             {
-                // Projections are not injective in general.
                 return ControlFlow::Continue(());
             }
-            ty::Alias(ty::Weak, alias) if !self.include_nonconstraining => {
-                if !self.tcx.recursion_limit().value_within_limit(self.depth) {
-                    // Other constituent types may still constrain some generic params, consider
-                    // `<T> (Overflow, T)` for example. Therefore we want to continue instead of
-                    // breaking. Only affects diagnostics.
-                    return ControlFlow::Continue(());
-                }
-                self.depth += 1;
-                return ensure_sufficient_stack(|| {
-                    self.tcx
-                        .type_of(alias.def_id)
-                        .instantiate(self.tcx, alias.args)
-                        .visit_with(self)
-                });
-            }
-            ty::Param(data) => {
-                self.parameters.push(Parameter::from(data));
+            // All weak alias types should've been expanded beforehand.
+            ty::Alias(ty::Weak, _) if !self.include_nonconstraining => {
+                bug!("unexpected weak alias type")
             }
+            ty::Param(param) => self.parameters.push(Parameter::from(param)),
             _ => {}
         }
 
@@ -224,12 +209,12 @@ pub fn setup_constraining_predicates<'tcx>(
                 //     `<<T as Bar>::Baz as Iterator>::Output = <U as Iterator>::Output`
                 // Then the projection only applies if `T` is known, but it still
                 // does not determine `U`.
-                let inputs = parameters_for(tcx, &projection.projection_ty, true);
+                let inputs = parameters_for(tcx, projection.projection_ty, true);
                 let relies_only_on_inputs = inputs.iter().all(|p| input_parameters.contains(p));
                 if !relies_only_on_inputs {
                     continue;
                 }
-                input_parameters.extend(parameters_for(tcx, &projection.term, false));
+                input_parameters.extend(parameters_for(tcx, projection.term, false));
             } else {
                 continue;
             }

compiler/rustc_hir_analysis/src/impl_wf_check.rs

@@ -111,7 +111,7 @@ fn enforce_impl_params_are_constrained(
             match item.kind {
                 ty::AssocKind::Type => {
                     if item.defaultness(tcx).has_value() {
-                        cgp::parameters_for(tcx, &tcx.type_of(def_id).instantiate_identity(), true)
+                        cgp::parameters_for(tcx, tcx.type_of(def_id).instantiate_identity(), true)
                     } else {
                         vec![]
                     }

compiler/rustc_hir_analysis/src/impl_wf_check/min_specialization.rs

@@ -133,7 +133,7 @@ fn check_always_applicable(
 
     res = res.and(check_constness(tcx, impl1_def_id, impl2_node, span));
     res = res.and(check_static_lifetimes(tcx, &parent_args, span));
-    res = res.and(check_duplicate_params(tcx, impl1_args, &parent_args, span));
+    res = res.and(check_duplicate_params(tcx, impl1_args, parent_args, span));
     res = res.and(check_predicates(tcx, impl1_def_id, impl1_args, impl2_node, impl2_args, span));
 
     res
@@ -266,15 +266,15 @@ fn unconstrained_parent_impl_args<'tcx>(
                 continue;
             }
 
-            unconstrained_parameters.extend(cgp::parameters_for(tcx, &projection_ty, true));
+            unconstrained_parameters.extend(cgp::parameters_for(tcx, projection_ty, true));
 
-            for param in cgp::parameters_for(tcx, &projected_ty, false) {
+            for param in cgp::parameters_for(tcx, projected_ty, false) {
                 if !unconstrained_parameters.contains(&param) {
                     constrained_params.insert(param.0);
                 }
             }
 
-            unconstrained_parameters.extend(cgp::parameters_for(tcx, &projected_ty, true));
+            unconstrained_parameters.extend(cgp::parameters_for(tcx, projected_ty, true));
         }
     }
 
@@ -309,7 +309,7 @@ fn unconstrained_parent_impl_args<'tcx>(
 fn check_duplicate_params<'tcx>(
     tcx: TyCtxt<'tcx>,
     impl1_args: GenericArgsRef<'tcx>,
-    parent_args: &Vec<GenericArg<'tcx>>,
+    parent_args: Vec<GenericArg<'tcx>>,
     span: Span,
 ) -> Result<(), ErrorGuaranteed> {
     let mut base_params = cgp::parameters_for(tcx, parent_args, true);

compiler/rustc_infer/src/infer/error_reporting/nice_region_error/util.rs

@@ -5,7 +5,7 @@ use crate::infer::error_reporting::nice_region_error::NiceRegionError;
 use crate::infer::TyCtxt;
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;
-use rustc_middle::ty::{self, Binder, Region, Ty, TypeVisitable};
+use rustc_middle::ty::{self, Binder, Region, Ty, TypeFoldable};
 use rustc_span::Span;
 
 /// Information about the anonymous region we are searching for.
@@ -142,10 +142,10 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
 
     fn includes_region(
         &self,
-        ty: Binder<'tcx, impl TypeVisitable<TyCtxt<'tcx>>>,
+        ty: Binder<'tcx, impl TypeFoldable<TyCtxt<'tcx>>>,
         region: ty::BoundRegionKind,
     ) -> bool {
-        let late_bound_regions = self.tcx().collect_referenced_late_bound_regions(&ty);
+        let late_bound_regions = self.tcx().collect_referenced_late_bound_regions(ty);
         // We are only checking is any region meets the condition so order doesn't matter
         #[allow(rustc::potential_query_instability)]
         late_bound_regions.iter().any(|r| *r == region)

compiler/rustc_middle/src/arena.rs

@@ -47,7 +47,7 @@ macro_rules! arena_types {
                         rustc_middle::traits::query::DropckOutlivesResult<'tcx>
                     >
                 >,
-            [] normalize_projection_ty:
+            [] normalize_canonicalized_projection_ty:
                 rustc_middle::infer::canonical::Canonical<'tcx,
                     rustc_middle::infer::canonical::QueryResponse<'tcx,
                         rustc_middle::traits::query::NormalizationResult<'tcx>

compiler/rustc_middle/src/query/mod.rs

@@ -31,7 +31,7 @@ use crate::query::plumbing::{
 };
 use crate::thir;
 use crate::traits::query::{
-    CanonicalPredicateGoal, CanonicalProjectionGoal, CanonicalTyGoal,
+    CanonicalAliasGoal, CanonicalPredicateGoal, CanonicalTyGoal,
     CanonicalTypeOpAscribeUserTypeGoal, CanonicalTypeOpEqGoal, CanonicalTypeOpNormalizeGoal,
     CanonicalTypeOpProvePredicateGoal, CanonicalTypeOpSubtypeGoal, NoSolution,
 };
@@ -1931,29 +1931,41 @@ rustc_queries! {
         arena_cache
     }
 
-    /// Do not call this query directly: invoke `normalize` instead.
-    query normalize_projection_ty(
-        goal: CanonicalProjectionGoal<'tcx>
+    /// <div class="warning">
+    ///
+    /// Do not call this query directly: Invoke `normalize` instead.
+    ///
+    /// </div>
+    query normalize_canonicalized_projection_ty(
+        goal: CanonicalAliasGoal<'tcx>
     ) -> Result<
         &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, NormalizationResult<'tcx>>>,
         NoSolution,
     > {
         desc { "normalizing `{}`", goal.value.value }
     }
 
-    /// Do not call this query directly: invoke `normalize` instead.
-    query normalize_weak_ty(
-        goal: CanonicalProjectionGoal<'tcx>
+    /// <div class="warning">
+    ///
+    /// Do not call this query directly: Invoke `normalize` instead.
+    ///
+    /// </div>
+    query normalize_canonicalized_weak_ty(
+        goal: CanonicalAliasGoal<'tcx>
     ) -> Result<
         &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, NormalizationResult<'tcx>>>,
         NoSolution,
     > {
         desc { "normalizing `{}`", goal.value.value }
     }
 
-    /// Do not call this query directly: invoke `normalize` instead.
-    query normalize_inherent_projection_ty(
-        goal: CanonicalProjectionGoal<'tcx>
+    /// <div class="warning">
+    ///
+    /// Do not call this query directly: Invoke `normalize` instead.
+    ///
+    /// </div>
+    query normalize_canonicalized_inherent_projection_ty(
+        goal: CanonicalAliasGoal<'tcx>
     ) -> Result<
         &'tcx Canonical<'tcx, canonical::QueryResponse<'tcx, NormalizationResult<'tcx>>>,
         NoSolution,

compiler/rustc_middle/src/traits/query.rs

@@ -67,7 +67,7 @@ pub mod type_op {
     }
 }
 
-pub type CanonicalProjectionGoal<'tcx> = Canonical<'tcx, ty::ParamEnvAnd<'tcx, ty::AliasTy<'tcx>>>;
+pub type CanonicalAliasGoal<'tcx> = Canonical<'tcx, ty::ParamEnvAnd<'tcx, ty::AliasTy<'tcx>>>;
 
 pub type CanonicalTyGoal<'tcx> = Canonical<'tcx, ty::ParamEnvAnd<'tcx, Ty<'tcx>>>;
 
@@ -177,10 +177,10 @@ pub struct MethodAutoderefBadTy<'tcx> {
     pub ty: Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>,
 }
 
-/// Result from the `normalize_projection_ty` query.
+/// Result of the `normalize_canonicalized_{{,inherent_}projection,weak}_ty` queries.
 #[derive(Clone, Debug, HashStable, TypeFoldable, TypeVisitable)]
 pub struct NormalizationResult<'tcx> {
-    /// Result of normalization.
+    /// Result of the normalization.
     pub normalized_ty: Ty<'tcx>,
 }
 

compiler/rustc_middle/src/ty/flags.rs

@@ -181,9 +181,10 @@ impl FlagComputation {
 
             &ty::Alias(kind, data) => {
                 self.add_flags(match kind {
-                    ty::Weak | ty::Projection => TypeFlags::HAS_TY_PROJECTION,
-                    ty::Inherent => TypeFlags::HAS_TY_INHERENT,
+                    ty::Projection => TypeFlags::HAS_TY_PROJECTION,
+                    ty::Weak => TypeFlags::HAS_TY_WEAK,
                     ty::Opaque => TypeFlags::HAS_TY_OPAQUE,
+                    ty::Inherent => TypeFlags::HAS_TY_INHERENT,
                 });
 
                 self.add_alias_ty(data);