Rollup merge of #99821 - cjgillot:ast-lifetimes-2, r=compiler-errors

Remove separate indexing of early-bound regions

~Based on https://github.com/rust-lang/rust/pull/99728.~

This PR copies some modifications from https://github.com/rust-lang/rust/pull/97839 around object lifetime defaults.
These modifications allow to stop counting generic parameters during lifetime resolution, and rely on the indexing given by `rustc_typeck::collect`.

compiler/rustc_middle/src/hir/map/mod.rs

@@ -486,7 +486,9 @@ impl<'hir> Map<'hir> {
         let def_kind = self.tcx.def_kind(def_id);
         match def_kind {
             DefKind::Trait | DefKind::TraitAlias => def_id,
-            DefKind::TyParam | DefKind::ConstParam => self.tcx.local_parent(def_id),
+            DefKind::LifetimeParam | DefKind::TyParam | DefKind::ConstParam => {
+                self.tcx.local_parent(def_id)
+            }
             _ => bug!("ty_param_owner: {:?} is a {:?} not a type parameter", def_id, def_kind),
         }
     }
@@ -495,7 +497,9 @@ impl<'hir> Map<'hir> {
         let def_kind = self.tcx.def_kind(def_id);
         match def_kind {
             DefKind::Trait | DefKind::TraitAlias => kw::SelfUpper,
-            DefKind::TyParam | DefKind::ConstParam => self.tcx.item_name(def_id.to_def_id()),
+            DefKind::LifetimeParam | DefKind::TyParam | DefKind::ConstParam => {
+                self.tcx.item_name(def_id.to_def_id())
+            }
             _ => bug!("ty_param_name: {:?} is a {:?} not a type parameter", def_id, def_kind),
         }
     }

compiler/rustc_middle/src/middle/resolve_lifetime.rs

@@ -10,7 +10,7 @@ use rustc_macros::HashStable;
 #[derive(Clone, Copy, PartialEq, Eq, Hash, TyEncodable, TyDecodable, Debug, HashStable)]
 pub enum Region {
     Static,
-    EarlyBound(/* index */ u32, /* lifetime decl */ DefId),
+    EarlyBound(/* lifetime decl */ DefId),
     LateBound(ty::DebruijnIndex, /* late-bound index */ u32, /* lifetime decl */ DefId),
     Free(DefId, /* lifetime decl */ DefId),
 }
@@ -35,7 +35,13 @@ impl<T: PartialEq> Set1<T> {
     }
 }
 
-pub type ObjectLifetimeDefault = Set1<Region>;
+#[derive(Copy, Clone, Debug, HashStable, Encodable, Decodable)]
+pub enum ObjectLifetimeDefault {
+    Empty,
+    Static,
+    Ambiguous,
+    Param(DefId),
+}
 
 /// Maps the id of each lifetime reference to the lifetime decl
 /// that it corresponds to.

compiler/rustc_middle/src/query/mod.rs

@@ -1597,8 +1597,9 @@ 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>>> {

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 },
 }
 

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,