Compute `object_lifetime_default` per parameter.

9 files changed, 68 insertions, 109 deletions

diff --git a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
index 38ce50e8323..14a28cf7d3f 100644
--- a/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
+++ b/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs
@@ -199,6 +199,7 @@ provide! { <'tcx> tcx, def_id, other, cdata,
     codegen_fn_attrs => { table }
     impl_trait_ref => { table }
     const_param_default => { table }
+    object_lifetime_default => { table }
     thir_abstract_const => { table }
     optimized_mir => { table }
     mir_for_ctfe => { table }
diff --git a/compiler/rustc_metadata/src/rmeta/encoder.rs b/compiler/rustc_metadata/src/rmeta/encoder.rs
index 33278367ce3..50a309f8785 100644
--- a/compiler/rustc_metadata/src/rmeta/encoder.rs
+++ b/compiler/rustc_metadata/src/rmeta/encoder.rs
@@ -1044,6 +1044,11 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
                     record_array!(self.tables.inferred_outlives_of[def_id] <- inferred_outlives);
                 }
             }
+            if let DefKind::TyParam | DefKind::ConstParam = def_kind {
+                if let Some(default) = self.tcx.object_lifetime_default(def_id) {
+                    record!(self.tables.object_lifetime_default[def_id] <- default);
+                }
+            }
             if let DefKind::Trait | DefKind::TraitAlias = def_kind {
                 record!(self.tables.super_predicates_of[def_id] <- self.tcx.super_predicates_of(def_id));
             }
diff --git a/compiler/rustc_metadata/src/rmeta/mod.rs b/compiler/rustc_metadata/src/rmeta/mod.rs
index 66bdecc30db..2f3493d1b19 100644
--- a/compiler/rustc_metadata/src/rmeta/mod.rs
+++ b/compiler/rustc_metadata/src/rmeta/mod.rs
@@ -16,6 +16,7 @@ use rustc_index::{bit_set::FiniteBitSet, vec::IndexVec};
 use rustc_middle::metadata::ModChild;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrs;
 use rustc_middle::middle::exported_symbols::{ExportedSymbol, SymbolExportInfo};
+use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
 use rustc_middle::mir;
 use rustc_middle::ty::fast_reject::SimplifiedType;
 use rustc_middle::ty::query::Providers;
@@ -357,6 +358,7 @@ define_tables! {
     codegen_fn_attrs: Table<DefIndex, LazyValue<CodegenFnAttrs>>,
     impl_trait_ref: Table<DefIndex, LazyValue<ty::TraitRef<'static>>>,
     const_param_default: Table<DefIndex, LazyValue<rustc_middle::ty::Const<'static>>>,
+    object_lifetime_default: Table<DefIndex, LazyValue<ObjectLifetimeDefault>>,
     optimized_mir: Table<DefIndex, LazyValue<mir::Body<'static>>>,
     mir_for_ctfe: Table<DefIndex, LazyValue<mir::Body<'static>>>,
     promoted_mir: Table<DefIndex, LazyValue<IndexVec<mir::Promoted, mir::Body<'static>>>>,
diff --git a/compiler/rustc_middle/src/query/mod.rs b/compiler/rustc_middle/src/query/mod.rs
index d8483e7e409..ff296116a1f 100644
--- a/compiler/rustc_middle/src/query/mod.rs
+++ b/compiler/rustc_middle/src/query/mod.rs
@@ -1579,8 +1579,9 @@ rustc_queries! {
     /// for each parameter if a trait object were to be passed for that parameter.
     /// For example, for `struct Foo<'a, T, U>`, this would be `['static, 'static]`.
     /// For `struct Foo<'a, T: 'a, U>`, this would instead be `['a, 'static]`.
-    query object_lifetime_defaults(_: LocalDefId) -> Option<&'tcx [ObjectLifetimeDefault]> {
-        desc { "looking up lifetime defaults for a region on an item" }
+    query object_lifetime_default(key: DefId) -> Option<ObjectLifetimeDefault> {
+        desc { "looking up lifetime defaults for generic parameter `{:?}`", key }
+        separate_provide_extern
     }
     query late_bound_vars_map(_: LocalDefId)
         -> Option<&'tcx FxHashMap<ItemLocalId, Vec<ty::BoundVariableKind>>> {
diff --git a/compiler/rustc_middle/src/ty/generics.rs b/compiler/rustc_middle/src/ty/generics.rs
index add2df25884..d6a55af51e5 100644
--- a/compiler/rustc_middle/src/ty/generics.rs
+++ b/compiler/rustc_middle/src/ty/generics.rs
@@ -1,4 +1,3 @@
-use crate::middle::resolve_lifetime::ObjectLifetimeDefault;
 use crate::ty;
 use crate::ty::subst::{Subst, SubstsRef};
 use crate::ty::EarlyBinder;
@@ -13,7 +12,7 @@ use super::{EarlyBoundRegion, InstantiatedPredicates, ParamConst, ParamTy, Predi
 #[derive(Clone, Debug, TyEncodable, TyDecodable, HashStable)]
 pub enum GenericParamDefKind {
     Lifetime,
-    Type { has_default: bool, object_lifetime_default: ObjectLifetimeDefault, synthetic: bool },
+    Type { has_default: bool, synthetic: bool },
     Const { has_default: bool },
 }
 
diff --git a/compiler/rustc_middle/src/ty/parameterized.rs b/compiler/rustc_middle/src/ty/parameterized.rs
index e189ee2fc4d..067ad927a03 100644
--- a/compiler/rustc_middle/src/ty/parameterized.rs
+++ b/compiler/rustc_middle/src/ty/parameterized.rs
@@ -53,6 +53,7 @@ trivially_parameterized_over_tcx! {
     crate::metadata::ModChild,
     crate::middle::codegen_fn_attrs::CodegenFnAttrs,
     crate::middle::exported_symbols::SymbolExportInfo,
+    crate::middle::resolve_lifetime::ObjectLifetimeDefault,
     crate::mir::ConstQualifs,
     ty::Generics,
     ty::ImplPolarity,
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index fde12b9eee6..33ab2e12edd 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -16,6 +16,7 @@ use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{self, FnSig, ForeignItem, HirId, Item, ItemKind, TraitItem, CRATE_HIR_ID};
 use rustc_hir::{MethodKind, Target};
 use rustc_middle::hir::nested_filter;
+use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::TyCtxt;
 use rustc_session::lint::builtin::{
@@ -171,6 +172,9 @@ impl CheckAttrVisitor<'_> {
                 sym::no_implicit_prelude => {
                     self.check_generic_attr(hir_id, attr, target, &[Target::Mod])
                 }
+                sym::rustc_object_lifetime_default => {
+                    self.check_object_lifetime_default(hir_id, span)
+                }
                 _ => {}
             }
 
@@ -402,6 +406,30 @@ impl CheckAttrVisitor<'_> {
         }
     }
 
+    /// Debugging aid for `object_lifetime_default` query.
+    fn check_object_lifetime_default(&self, hir_id: HirId, span: Span) {
+        let tcx = self.tcx;
+        if let Some(generics) = tcx.hir().get_generics(tcx.hir().local_def_id(hir_id)) {
+            let object_lifetime_default_reprs: String = generics
+                .params
+                .iter()
+                .filter_map(|p| {
+                    let param_id = tcx.hir().local_def_id(p.hir_id);
+                    let default = tcx.object_lifetime_default(param_id)?;
+                    Some(match default {
+                        ObjectLifetimeDefault::Empty => "BaseDefault".to_owned(),
+                        ObjectLifetimeDefault::Static => "'static".to_owned(),
+                        ObjectLifetimeDefault::Param(def_id) => tcx.item_name(def_id).to_string(),
+                        ObjectLifetimeDefault::Ambiguous => "Ambiguous".to_owned(),
+                    })
+                })
+                .collect::<Vec<String>>()
+                .join(",");
+
+            tcx.sess.span_err(span, &object_lifetime_default_reprs);
+        }
+    }
+
     /// Checks if a `#[track_caller]` is applied to a non-naked function. Returns `true` if valid.
     fn check_track_caller(
         &self,
diff --git a/compiler/rustc_resolve/src/late/lifetimes.rs b/compiler/rustc_resolve/src/late/lifetimes.rs
index b96968f81e0..52980f15971 100644
--- a/compiler/rustc_resolve/src/late/lifetimes.rs
+++ b/compiler/rustc_resolve/src/late/lifetimes.rs
@@ -18,11 +18,10 @@ use rustc_middle::bug;
 use rustc_middle::hir::map::Map;
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::resolve_lifetime::*;
-use rustc_middle::ty::{self, GenericParamDefKind, TyCtxt};
+use rustc_middle::ty::{self, DefIdTree, TyCtxt};
 use rustc_span::def_id::DefId;
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
-use std::borrow::Cow;
 use std::fmt;
 
 trait RegionExt {
@@ -290,7 +289,7 @@ pub fn provide(providers: &mut ty::query::Providers) {
 
         named_region_map: |tcx, id| resolve_lifetimes_for(tcx, id).defs.get(&id),
         is_late_bound_map,
-        object_lifetime_defaults,
+        object_lifetime_default,
         late_bound_vars_map: |tcx, id| resolve_lifetimes_for(tcx, id).late_bound_vars.get(&id),
 
         ..*providers
@@ -1264,87 +1263,36 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
     }
 }
 
-fn object_lifetime_defaults<'tcx>(
+fn object_lifetime_default<'tcx>(
     tcx: TyCtxt<'tcx>,
-    def_id: LocalDefId,
-) -> Option<&'tcx [ObjectLifetimeDefault]> {
-    let hir::Node::Item(item) = tcx.hir().get_by_def_id(def_id) else { return None; };
-    match item.kind {
-        hir::ItemKind::Struct(_, ref generics)
-        | hir::ItemKind::Union(_, ref generics)
-        | hir::ItemKind::Enum(_, ref generics)
-        | hir::ItemKind::OpaqueTy(hir::OpaqueTy {
-            ref generics,
-            origin: hir::OpaqueTyOrigin::TyAlias,
-            ..
-        })
-        | hir::ItemKind::TyAlias(_, ref generics)
-        | hir::ItemKind::Trait(_, _, ref generics, ..) => {
-            let result = object_lifetime_defaults_for_item(tcx, generics);
-
-            // Debugging aid.
-            let attrs = tcx.hir().attrs(item.hir_id());
-            if tcx.sess.contains_name(attrs, sym::rustc_object_lifetime_default) {
-                let object_lifetime_default_reprs: String = result
-                    .iter()
-                    .map(|set| match *set {
-                        ObjectLifetimeDefault::Empty => "BaseDefault".into(),
-                        ObjectLifetimeDefault::Static => "'static".into(),
-                        ObjectLifetimeDefault::Param(def_id) => {
-                            let def_id = def_id.expect_local();
-                            tcx.hir().ty_param_name(def_id).to_string().into()
-                        }
-                        ObjectLifetimeDefault::Ambiguous => "Ambiguous".into(),
-                    })
-                    .collect::<Vec<Cow<'static, str>>>()
-                    .join(",");
-                tcx.sess.span_err(item.span, &object_lifetime_default_reprs);
-            }
-
-            Some(result)
-        }
-        _ => None,
-    }
-}
-
-/// Scan the bounds and where-clauses on parameters to extract bounds
-/// of the form `T:'a` so as to determine the `ObjectLifetimeDefault`
-/// for each type parameter.
-fn object_lifetime_defaults_for_item<'tcx>(
-    tcx: TyCtxt<'tcx>,
-    generics: &hir::Generics<'_>,
-) -> &'tcx [ObjectLifetimeDefault] {
-    fn add_bounds(set: &mut Set1<hir::LifetimeName>, bounds: &[hir::GenericBound<'_>]) {
-        for bound in bounds {
-            if let hir::GenericBound::Outlives(ref lifetime) = *bound {
-                set.insert(lifetime.name.normalize_to_macros_2_0());
-            }
-        }
-    }
-
-    let process_param = |param: &hir::GenericParam<'_>| match param.kind {
+    param_def_id: DefId,
+) -> Option<ObjectLifetimeDefault> {
+    let param_def_id = param_def_id.expect_local();
+    let parent_def_id = tcx.local_parent(param_def_id);
+    let generics = tcx.hir().get_generics(parent_def_id)?;
+    let param_hir_id = tcx.local_def_id_to_hir_id(param_def_id);
+    let param = generics.params.iter().find(|p| p.hir_id == param_hir_id)?;
+
+    // Scan the bounds and where-clauses on parameters to extract bounds
+    // of the form `T:'a` so as to determine the `ObjectLifetimeDefault`
+    // for each type parameter.
+    match param.kind {
         GenericParamKind::Lifetime { .. } => None,
         GenericParamKind::Type { .. } => {
             let mut set = Set1::Empty;
 
-            let param_def_id = tcx.hir().local_def_id(param.hir_id);
-            for predicate in generics.predicates {
-                // Look for `type: ...` where clauses.
-                let hir::WherePredicate::BoundPredicate(ref data) = *predicate else { continue };
-
+            // Look for `type: ...` where clauses.
+            for bound in generics.bounds_for_param(param_def_id) {
                 // Ignore `for<'a> type: ...` as they can change what
                 // lifetimes mean (although we could "just" handle it).
-                if !data.bound_generic_params.is_empty() {
+                if !bound.bound_generic_params.is_empty() {
                     continue;
                 }
 
-                let res = match data.bounded_ty.kind {
-                    hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => path.res,
-                    _ => continue,
-                };
-
-                if res == Res::Def(DefKind::TyParam, param_def_id.to_def_id()) {
-                    add_bounds(&mut set, &data.bounds);
+                for bound in bound.bounds {
+                    if let hir::GenericBound::Outlives(ref lifetime) = *bound {
+                        set.insert(lifetime.name.normalize_to_macros_2_0());
+                    }
                 }
             }
 
@@ -1364,9 +1312,7 @@ fn object_lifetime_defaults_for_item<'tcx>(
             // in an arbitrary order.
             Some(ObjectLifetimeDefault::Empty)
         }
-    };
-
-    tcx.arena.alloc_from_iter(generics.params.iter().filter_map(process_param))
+    }
 }
 
 impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
@@ -1744,13 +1690,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             generics
                 .params
                 .iter()
-                .filter_map(|param| match param.kind {
-                    GenericParamDefKind::Type { object_lifetime_default, .. } => {
-                        Some(object_lifetime_default)
-                    }
-                    GenericParamDefKind::Const { .. } => Some(ObjectLifetimeDefault::Empty),
-                    GenericParamDefKind::Lifetime => None,
-                })
+                .filter_map(|param| self.tcx.object_lifetime_default(param.def_id))
                 .map(set_to_region)
                 .collect()
         });
diff --git a/compiler/rustc_typeck/src/collect.rs b/compiler/rustc_typeck/src/collect.rs
index 1c1df4a2f7f..0ec2acafd07 100644
--- a/compiler/rustc_typeck/src/collect.rs
+++ b/compiler/rustc_typeck/src/collect.rs
@@ -34,7 +34,6 @@ use rustc_hir::weak_lang_items;
 use rustc_hir::{GenericParamKind, HirId, Node};
 use rustc_middle::hir::nested_filter;
 use rustc_middle::middle::codegen_fn_attrs::{CodegenFnAttrFlags, CodegenFnAttrs};
-use rustc_middle::middle::resolve_lifetime::ObjectLifetimeDefault;
 use rustc_middle::mir::mono::Linkage;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::InternalSubsts;
@@ -1598,7 +1597,6 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
                         pure_wrt_drop: false,
                         kind: ty::GenericParamDefKind::Type {
                             has_default: false,
-                            object_lifetime_default: ObjectLifetimeDefault::Empty,
                             synthetic: false,
                         },
                     });
@@ -1642,8 +1640,6 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
         kind: ty::GenericParamDefKind::Lifetime,
     }));
 
-    let object_lifetime_defaults = tcx.object_lifetime_defaults(hir_id.owner);
-
     // Now create the real type and const parameters.
     let type_start = own_start - has_self as u32 + params.len() as u32;
     let mut i = 0;
@@ -1668,13 +1664,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
                 }
             }
 
-            let kind = ty::GenericParamDefKind::Type {
-                has_default: default.is_some(),
-                object_lifetime_default: object_lifetime_defaults
-                    .as_ref()
-                    .map_or(ObjectLifetimeDefault::Empty, |o| o[i]),
-                synthetic,
-            };
+            let kind = ty::GenericParamDefKind::Type { has_default: default.is_some(), synthetic };
 
             let param_def = ty::GenericParamDef {
                 index: type_start + i as u32,
@@ -1726,11 +1716,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
             name: Symbol::intern(arg),
             def_id,
             pure_wrt_drop: false,
-            kind: ty::GenericParamDefKind::Type {
-                has_default: false,
-                object_lifetime_default: ObjectLifetimeDefault::Empty,
-                synthetic: false,
-            },
+            kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
         }));
     }
 
@@ -1743,11 +1729,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> ty::Generics {
                 name: Symbol::intern("<const_ty>"),
                 def_id,
                 pure_wrt_drop: false,
-                kind: ty::GenericParamDefKind::Type {
-                    has_default: false,
-                    object_lifetime_default: ObjectLifetimeDefault::Empty,
-                    synthetic: false,
-                },
+                kind: ty::GenericParamDefKind::Type { has_default: false, synthetic: false },
             });
         }
     }