Rollup merge of #127045 - compiler-errors:explicit, r=oli-obk

Rename `super_predicates_of` and similar queries to `explicit_*` to note that they're not elaborated

Rename:
* `super_predicates_of` -> `explicit_super_predicates_of`
* `implied_predicates_of` -> `explicit_implied_predicates_of`
* `supertraits_containing_assoc_item` -> `explicit_supertraits_containing_assoc_item`

This makes it clearer that, unlike (for example) [`TyCtxt::super_traits_of`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/context/struct.TyCtxt.html#method.super_traits_of), we don't automatically elaborate this set of predicates.

r? ``@lcnr`` or ``@oli-obk`` or someone from t-types idc

compiler/rustc_hir_analysis/src/collect.rs

@@ -70,10 +70,10 @@ pub fn provide(providers: &mut Providers) {
         predicates_of: predicates_of::predicates_of,
         predicates_defined_on,
         explicit_predicates_of: predicates_of::explicit_predicates_of,
-        super_predicates_of: predicates_of::super_predicates_of,
-        implied_predicates_of: predicates_of::implied_predicates_of,
-        super_predicates_that_define_assoc_item:
-            predicates_of::super_predicates_that_define_assoc_item,
+        explicit_super_predicates_of: predicates_of::explicit_super_predicates_of,
+        explicit_implied_predicates_of: predicates_of::explicit_implied_predicates_of,
+        explicit_supertraits_containing_assoc_item:
+            predicates_of::explicit_supertraits_containing_assoc_item,
         trait_explicit_predicates_and_bounds: predicates_of::trait_explicit_predicates_and_bounds,
         type_param_predicates: predicates_of::type_param_predicates,
         trait_def,
@@ -691,14 +691,14 @@ fn lower_item(tcx: TyCtxt<'_>, item_id: hir::ItemId) {
         hir::ItemKind::Trait(..) => {
             tcx.ensure().generics_of(def_id);
             tcx.ensure().trait_def(def_id);
-            tcx.at(it.span).super_predicates_of(def_id);
+            tcx.at(it.span).explicit_super_predicates_of(def_id);
             tcx.ensure().predicates_of(def_id);
             tcx.ensure().associated_items(def_id);
         }
         hir::ItemKind::TraitAlias(..) => {
             tcx.ensure().generics_of(def_id);
-            tcx.at(it.span).implied_predicates_of(def_id);
-            tcx.at(it.span).super_predicates_of(def_id);
+            tcx.at(it.span).explicit_implied_predicates_of(def_id);
+            tcx.at(it.span).explicit_super_predicates_of(def_id);
             tcx.ensure().predicates_of(def_id);
         }
         hir::ItemKind::Struct(struct_def, _) | hir::ItemKind::Union(struct_def, _) => {

compiler/rustc_hir_analysis/src/collect/predicates_of.rs

@@ -519,21 +519,21 @@ pub(super) fn explicit_predicates_of<'tcx>(
 /// Ensures that the super-predicates of the trait with a `DefId`
 /// of `trait_def_id` are lowered and stored. This also ensures that
 /// the transitive super-predicates are lowered.
-pub(super) fn super_predicates_of(
+pub(super) fn explicit_super_predicates_of(
     tcx: TyCtxt<'_>,
     trait_def_id: LocalDefId,
 ) -> ty::GenericPredicates<'_> {
     implied_predicates_with_filter(tcx, trait_def_id.to_def_id(), PredicateFilter::SelfOnly)
 }
 
-pub(super) fn super_predicates_that_define_assoc_item(
+pub(super) fn explicit_supertraits_containing_assoc_item(
     tcx: TyCtxt<'_>,
     (trait_def_id, assoc_name): (DefId, Ident),
 ) -> ty::GenericPredicates<'_> {
     implied_predicates_with_filter(tcx, trait_def_id, PredicateFilter::SelfThatDefines(assoc_name))
 }
 
-pub(super) fn implied_predicates_of(
+pub(super) fn explicit_implied_predicates_of(
     tcx: TyCtxt<'_>,
     trait_def_id: LocalDefId,
 ) -> ty::GenericPredicates<'_> {
@@ -560,7 +560,7 @@ pub(super) fn implied_predicates_with_filter(
         // if `assoc_name` is None, then the query should've been redirected to an
         // external provider
         assert!(matches!(filter, PredicateFilter::SelfThatDefines(_)));
-        return tcx.super_predicates_of(trait_def_id);
+        return tcx.explicit_super_predicates_of(trait_def_id);
     };
 
     let Node::Item(item) = tcx.hir_node_by_def_id(trait_def_id) else {
@@ -601,7 +601,7 @@ pub(super) fn implied_predicates_with_filter(
                 if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder()
                     && bound.polarity == ty::PredicatePolarity::Positive
                 {
-                    tcx.at(span).super_predicates_of(bound.def_id());
+                    tcx.at(span).explicit_super_predicates_of(bound.def_id());
                 }
             }
         }
@@ -611,7 +611,7 @@ pub(super) fn implied_predicates_with_filter(
                 if let ty::ClauseKind::Trait(bound) = pred.kind().skip_binder()
                     && bound.polarity == ty::PredicatePolarity::Positive
                 {
-                    tcx.at(span).implied_predicates_of(bound.def_id());
+                    tcx.at(span).explicit_implied_predicates_of(bound.def_id());
                 }
             }
         }

compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -1760,7 +1760,7 @@ impl<'a, 'tcx> BoundVarContext<'a, 'tcx> {
             if let Some(assoc_item) = trait_defines_associated_item_named(def_id) {
                 break Some((bound_vars.into_iter().collect(), assoc_item));
             }
-            let predicates = tcx.super_predicates_that_define_assoc_item((def_id, assoc_name));
+            let predicates = tcx.explicit_supertraits_containing_assoc_item((def_id, assoc_name));
             let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| {
                 let bound_predicate = pred.kind();
                 match bound_predicate.skip_binder() {

compiler/rustc_infer/src/traits/util.rs

@@ -275,10 +275,10 @@ impl<'tcx, O: Elaboratable<'tcx>> Elaborator<'tcx, O> {
                 }
                 // Get predicates implied by the trait, or only super predicates if we only care about self predicates.
                 let predicates = match self.mode {
-                    Filter::All => tcx.implied_predicates_of(data.def_id()),
-                    Filter::OnlySelf => tcx.super_predicates_of(data.def_id()),
+                    Filter::All => tcx.explicit_implied_predicates_of(data.def_id()),
+                    Filter::OnlySelf => tcx.explicit_super_predicates_of(data.def_id()),
                     Filter::OnlySelfThatDefines(ident) => {
-                        tcx.super_predicates_that_define_assoc_item((data.def_id(), ident))
+                        tcx.explicit_supertraits_containing_assoc_item((data.def_id(), ident))
                     }
                 };
 
@@ -420,7 +420,7 @@ pub fn transitive_bounds<'tcx>(
 
 /// A specialized variant of `elaborate` that only elaborates trait references that may
 /// define the given associated item with the name `assoc_name`. It uses the
-/// `super_predicates_that_define_assoc_item` query to avoid enumerating super-predicates that
+/// `explicit_supertraits_containing_assoc_item` query to avoid enumerating super-predicates that
 /// aren't related to `assoc_item`. This is used when resolving types like `Self::Item` or
 /// `T::Item` and helps to avoid cycle errors (see e.g. #35237).
 pub fn transitive_bounds_that_define_assoc_item<'tcx>(

compiler/rustc_lint/src/multiple_supertrait_upcastable.rs

@@ -45,7 +45,7 @@ impl<'tcx> LateLintPass<'tcx> for MultipleSupertraitUpcastable {
         {
             let direct_super_traits_iter = cx
                 .tcx
-                .super_predicates_of(def_id)
+                .explicit_super_predicates_of(def_id)
                 .predicates
                 .into_iter()
                 .filter_map(|(pred, _)| pred.as_trait_clause());

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -211,8 +211,8 @@ provide! { tcx, def_id, other, cdata,
     explicit_predicates_of => { table }
     generics_of => { table }
     inferred_outlives_of => { table_defaulted_array }
-    super_predicates_of => { table }
-    implied_predicates_of => { table }
+    explicit_super_predicates_of => { table }
+    explicit_implied_predicates_of => { table }
     type_of => { table }
     type_alias_is_lazy => { cdata.root.tables.type_alias_is_lazy.get(cdata, def_id.index) }
     variances_of => { table }

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1431,17 +1431,17 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             }
             if let DefKind::Trait = def_kind {
                 record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
-                record!(self.tables.super_predicates_of[def_id] <- self.tcx.super_predicates_of(def_id));
-                record!(self.tables.implied_predicates_of[def_id] <- self.tcx.implied_predicates_of(def_id));
+                record!(self.tables.explicit_super_predicates_of[def_id] <- self.tcx.explicit_super_predicates_of(def_id));
+                record!(self.tables.explicit_implied_predicates_of[def_id] <- self.tcx.explicit_implied_predicates_of(def_id));
 
                 let module_children = self.tcx.module_children_local(local_id);
                 record_array!(self.tables.module_children_non_reexports[def_id] <-
                     module_children.iter().map(|child| child.res.def_id().index));
             }
             if let DefKind::TraitAlias = def_kind {
                 record!(self.tables.trait_def[def_id] <- self.tcx.trait_def(def_id));
-                record!(self.tables.super_predicates_of[def_id] <- self.tcx.super_predicates_of(def_id));
-                record!(self.tables.implied_predicates_of[def_id] <- self.tcx.implied_predicates_of(def_id));
+                record!(self.tables.explicit_super_predicates_of[def_id] <- self.tcx.explicit_super_predicates_of(def_id));
+                record!(self.tables.explicit_implied_predicates_of[def_id] <- self.tcx.explicit_implied_predicates_of(def_id));
             }
             if let DefKind::Trait | DefKind::Impl { .. } = def_kind {
                 let associated_item_def_ids = self.tcx.associated_item_def_ids(def_id);

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -416,10 +416,10 @@ define_tables! {
     lookup_deprecation_entry: Table<DefIndex, LazyValue<attr::Deprecation>>,
     explicit_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
     generics_of: Table<DefIndex, LazyValue<ty::Generics>>,
-    super_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
+    explicit_super_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
     // As an optimization, we only store this for trait aliases,
-    // since it's identical to super_predicates_of for traits.
-    implied_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
+    // since it's identical to explicit_super_predicates_of for traits.
+    explicit_implied_predicates_of: Table<DefIndex, LazyValue<ty::GenericPredicates<'static>>>,
     type_of: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, Ty<'static>>>>,
     variances_of: Table<DefIndex, LazyArray<ty::Variance>>,
     fn_sig: Table<DefIndex, LazyValue<ty::EarlyBinder<'static, ty::PolyFnSig<'static>>>>,

compiler/rustc_middle/src/query/mod.rs

@@ -646,6 +646,9 @@ rustc_queries! {
     }
 
     /// Returns the predicates written explicitly by the user.
+    ///
+    /// You should probably use `predicates_of` unless you're looking for
+    /// predicates with explicit spans for diagnostics purposes.
     query explicit_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
         desc { |tcx| "computing explicit predicates of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
@@ -662,29 +665,32 @@ rustc_queries! {
         feedable
     }
 
-    /// Maps from the `DefId` of a trait to the list of
-    /// super-predicates. This is a subset of the full list of
-    /// predicates. We store these in a separate map because we must
-    /// evaluate them even during type conversion, often before the
-    /// full predicates are available (note that supertraits have
-    /// additional acyclicity requirements).
-    query super_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
+    /// Maps from the `DefId` of a trait to the list of super-predicates of the trait,
+    /// *before* elaboration (so it doesn't contain transitive super-predicates). This
+    /// is a subset of the full list of predicates. We store these in a separate map
+    /// because we must evaluate them even during type conversion, often before the full
+    /// predicates are available (note that super-predicates must not be cyclic).
+    query explicit_super_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
         desc { |tcx| "computing the super predicates of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
     }
 
-    query implied_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
+    /// The predicates of the trait that are implied during elaboration. This is a
+    /// superset of the super-predicates of the trait, but a subset of the predicates
+    /// of the trait. For regular traits, this includes all super-predicates and their
+    /// associated type bounds. For trait aliases, currently, this includes all of the
+    /// predicates of the trait alias.
+    query explicit_implied_predicates_of(key: DefId) -> ty::GenericPredicates<'tcx> {
         desc { |tcx| "computing the implied predicates of `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }
         separate_provide_extern
     }
 
-    /// The `Option<Ident>` is the name of an associated type. If it is `None`, then this query
-    /// returns the full set of predicates. If `Some<Ident>`, then the query returns only the
-    /// subset of super-predicates that reference traits that define the given associated type.
-    /// This is used to avoid cycles in resolving types like `T::Item`.
-    query super_predicates_that_define_assoc_item(key: (DefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
+    /// The Ident is the name of an associated type.The query returns only the subset
+    /// of supertraits that define the given associated type. This is used to avoid
+    /// cycles in resolving type-dependent associated item paths like `T::Item`.
+    query explicit_supertraits_containing_assoc_item(key: (DefId, rustc_span::symbol::Ident)) -> ty::GenericPredicates<'tcx> {
         desc { |tcx| "computing the super traits of `{}` with associated type name `{}`",
             tcx.def_path_str(key.0),
             key.1

compiler/rustc_middle/src/traits/util.rs

@@ -35,7 +35,7 @@ struct Elaborator<'tcx> {
 impl<'tcx> Elaborator<'tcx> {
     fn elaborate(&mut self, trait_ref: PolyTraitRef<'tcx>) {
         let super_predicates =
-            self.tcx.super_predicates_of(trait_ref.def_id()).predicates.iter().filter_map(
+            self.tcx.explicit_super_predicates_of(trait_ref.def_id()).predicates.iter().filter_map(
                 |&(pred, _)| {
                     let clause = pred.instantiate_supertrait(self.tcx, trait_ref);
                     self.visited.insert(clause).then_some(clause)

compiler/rustc_middle/src/ty/context.rs

@@ -342,12 +342,15 @@ impl<'tcx> Interner for TyCtxt<'tcx> {
         )
     }
 
-    fn super_predicates_of(
+    fn explicit_super_predicates_of(
         self,
         def_id: DefId,
     ) -> ty::EarlyBinder<'tcx, impl IntoIterator<Item = ty::Clause<'tcx>>> {
         ty::EarlyBinder::bind(
-            self.super_predicates_of(def_id).instantiate_identity(self).predicates.into_iter(),
+            self.explicit_super_predicates_of(def_id)
+                .instantiate_identity(self)
+                .predicates
+                .into_iter(),
         )
     }
 
@@ -2440,7 +2443,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// Given the def_id of a Trait `trait_def_id` and the name of an associated item `assoc_name`
     /// returns true if the `trait_def_id` defines an associated item of name `assoc_name`.
     pub fn trait_may_define_assoc_item(self, trait_def_id: DefId, assoc_name: Ident) -> bool {
-        self.super_traits_of(trait_def_id).any(|trait_did| {
+        self.supertrait_def_ids(trait_def_id).any(|trait_did| {
             self.associated_items(trait_did)
                 .filter_by_name_unhygienic(assoc_name.name)
                 .any(|item| self.hygienic_eq(assoc_name, item.ident(self), trait_did))
@@ -2463,17 +2466,17 @@ impl<'tcx> TyCtxt<'tcx> {
 
     /// Computes the def-ids of the transitive supertraits of `trait_def_id`. This (intentionally)
     /// does not compute the full elaborated super-predicates but just the set of def-ids. It is used
-    /// to identify which traits may define a given associated type to help avoid cycle errors.
-    /// Returns a `DefId` iterator.
-    fn super_traits_of(self, trait_def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
+    /// to identify which traits may define a given associated type to help avoid cycle errors,
+    /// and to make size estimates for vtable layout computation.
+    pub fn supertrait_def_ids(self, trait_def_id: DefId) -> impl Iterator<Item = DefId> + 'tcx {
         let mut set = FxHashSet::default();
         let mut stack = vec![trait_def_id];
 
         set.insert(trait_def_id);
 
         iter::from_fn(move || -> Option<DefId> {
             let trait_did = stack.pop()?;
-            let generic_predicates = self.super_predicates_of(trait_did);
+            let generic_predicates = self.explicit_super_predicates_of(trait_did);
 
             for (predicate, _) in generic_predicates.predicates {
                 if let ty::ClauseKind::Trait(data) = predicate.kind().skip_binder() {

compiler/rustc_middle/src/ty/vtable.rs

@@ -3,8 +3,6 @@ use std::fmt;
 use crate::mir::interpret::{alloc_range, AllocId, Allocation, Pointer, Scalar};
 use crate::ty::{self, Instance, PolyTraitRef, Ty, TyCtxt};
 use rustc_ast::Mutability;
-use rustc_data_structures::fx::FxHashSet;
-use rustc_hir::def_id::DefId;
 use rustc_macros::HashStable;
 
 #[derive(Clone, Copy, PartialEq, HashStable)]
@@ -42,45 +40,12 @@ impl<'tcx> fmt::Debug for VtblEntry<'tcx> {
 impl<'tcx> TyCtxt<'tcx> {
     pub const COMMON_VTABLE_ENTRIES: &'tcx [VtblEntry<'tcx>] =
         &[VtblEntry::MetadataDropInPlace, VtblEntry::MetadataSize, VtblEntry::MetadataAlign];
-
-    pub fn supertrait_def_ids(self, trait_def_id: DefId) -> SupertraitDefIds<'tcx> {
-        SupertraitDefIds {
-            tcx: self,
-            stack: vec![trait_def_id],
-            visited: Some(trait_def_id).into_iter().collect(),
-        }
-    }
 }
 
 pub const COMMON_VTABLE_ENTRIES_DROPINPLACE: usize = 0;
 pub const COMMON_VTABLE_ENTRIES_SIZE: usize = 1;
 pub const COMMON_VTABLE_ENTRIES_ALIGN: usize = 2;
 
-pub struct SupertraitDefIds<'tcx> {
-    tcx: TyCtxt<'tcx>,
-    stack: Vec<DefId>,
-    visited: FxHashSet<DefId>,
-}
-
-impl Iterator for SupertraitDefIds<'_> {
-    type Item = DefId;
-
-    fn next(&mut self) -> Option<DefId> {
-        let def_id = self.stack.pop()?;
-        let predicates = self.tcx.super_predicates_of(def_id);
-        let visited = &mut self.visited;
-        self.stack.extend(
-            predicates
-                .predicates
-                .iter()
-                .filter_map(|(pred, _)| pred.as_trait_clause())
-                .map(|trait_ref| trait_ref.def_id())
-                .filter(|&super_def_id| visited.insert(super_def_id)),
-        );
-        Some(def_id)
-    }
-}
-
 // Note that we don't have access to a self type here, this has to be purely based on the trait (and
 // supertrait) definitions. That means we can't call into the same vtable_entries code since that
 // returns a specific instantiation (e.g., with Vacant slots when bounds aren't satisfied). The goal

compiler/rustc_next_trait_solver/src/solve/assembly/structural_traits.rs

@@ -668,8 +668,9 @@ where
 {
     let cx = ecx.cx();
     let mut requirements = vec![];
-    requirements
-        .extend(cx.super_predicates_of(trait_ref.def_id).iter_instantiated(cx, trait_ref.args));
+    requirements.extend(
+        cx.explicit_super_predicates_of(trait_ref.def_id).iter_instantiated(cx, trait_ref.args),
+    );
 
     // FIXME(associated_const_equality): Also add associated consts to
     // the requirements here.

compiler/rustc_trait_selection/src/traits/object_safety.rs

@@ -187,7 +187,7 @@ fn predicates_reference_self(
 ) -> SmallVec<[Span; 1]> {
     let trait_ref = ty::Binder::dummy(ty::TraitRef::identity(tcx, trait_def_id));
     let predicates = if supertraits_only {
-        tcx.super_predicates_of(trait_def_id)
+        tcx.explicit_super_predicates_of(trait_def_id)
     } else {
         tcx.predicates_of(trait_def_id)
     };
@@ -256,7 +256,7 @@ fn super_predicates_have_non_lifetime_binders(
     if !tcx.features().non_lifetime_binders {
         return SmallVec::new();
     }
-    tcx.super_predicates_of(trait_def_id)
+    tcx.explicit_super_predicates_of(trait_def_id)
         .predicates
         .iter()
         .filter_map(|(pred, span)| pred.has_non_region_bound_vars().then_some(*span))

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -574,7 +574,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // Check supertraits hold. This is so that their associated type bounds
         // will be checked in the code below.
         for super_trait in tcx
-            .super_predicates_of(trait_predicate.def_id())
+            .explicit_super_predicates_of(trait_predicate.def_id())
             .instantiate(tcx, trait_predicate.trait_ref.args)
             .predicates
             .into_iter()