Auto merge of rust-lang#91557 - cjgillot:ast-lifetimes-named, r=petrochenkov

Perform lifetime resolution on the AST for lowering

Lifetime resolution is currently implemented several times. Once during lowering in order to introduce in-band lifetimes, and once in the resolve_lifetimes query. However, due to the global nature of lifetime resolution and how it interferes with hygiene, it is better suited on the AST.

This PR implements a first draft of lifetime resolution on the AST. For now, we specifically target named lifetimes and everything we need to remove lifetime resolution from lowering. Some diagnostics have already been ported, and sometimes made more precise using available hygiene information. Follow-up PRs will address in particular the resolution of anonymous lifetimes on the AST.

We reuse the rib design of the current resolution framework. Specific `LifetimeRib` and `LifetimeRibKind` types are introduced. The most important variant is `LifetimeRibKind::Generics`, which happens each time we encounter something which may introduce generic lifetime parameters. It can be an item or a `for<...>` binder. The `LifetimeBinderKind` specifies how this rib behaves with respect to in-band lifetimes.

r? `@petrochenkov`

Author: bors

compiler/rustc_ast_lowering/src/expr.rs

@@ -53,7 +53,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         e.span,
                         seg,
                         ParamMode::Optional,
-                        0,
                         ParenthesizedGenericArgs::Err,
                         ImplTraitContext::Disallowed(ImplTraitPosition::Path),
                     ));

compiler/rustc_ast_lowering/src/index.rs

@@ -30,6 +30,7 @@ pub(super) struct NodeCollector<'a, 'hir> {
     definitions: &'a definitions::Definitions,
 }
 
+#[tracing::instrument(level = "debug", skip(sess, definitions, bodies))]
 pub(super) fn index_hir<'hir>(
     sess: &Session,
     definitions: &definitions::Definitions,
@@ -65,6 +66,7 @@ pub(super) fn index_hir<'hir>(
 }
 
 impl<'a, 'hir> NodeCollector<'a, 'hir> {
+    #[tracing::instrument(level = "debug", skip(self))]
     fn insert(&mut self, span: Span, hir_id: HirId, node: Node<'hir>) {
         debug_assert_eq!(self.owner, hir_id.owner);
         debug_assert_ne!(hir_id.local_id.as_u32(), 0);
@@ -138,8 +140,8 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
         });
     }
 
+    #[tracing::instrument(level = "debug", skip(self))]
     fn visit_item(&mut self, i: &'hir Item<'hir>) {
-        debug!("visit_item: {:?}", i);
         debug_assert_eq!(i.def_id, self.owner);
         self.with_parent(i.hir_id(), |this| {
             if let ItemKind::Struct(ref struct_def, _) = i.kind {
@@ -152,6 +154,7 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
         });
     }
 
+    #[tracing::instrument(level = "debug", skip(self))]
     fn visit_foreign_item(&mut self, fi: &'hir ForeignItem<'hir>) {
         debug_assert_eq!(fi.def_id, self.owner);
         self.with_parent(fi.hir_id(), |this| {
@@ -170,13 +173,15 @@ impl<'a, 'hir> Visitor<'hir> for NodeCollector<'a, 'hir> {
         })
     }
 
+    #[tracing::instrument(level = "debug", skip(self))]
     fn visit_trait_item(&mut self, ti: &'hir TraitItem<'hir>) {
         debug_assert_eq!(ti.def_id, self.owner);
         self.with_parent(ti.hir_id(), |this| {
             intravisit::walk_trait_item(this, ti);
         });
     }
 
+    #[tracing::instrument(level = "debug", skip(self))]
     fn visit_impl_item(&mut self, ii: &'hir ImplItem<'hir>) {
         debug_assert_eq!(ii.def_id, self.owner);
         self.with_parent(ii.hir_id(), |this| {

compiler/rustc_ast_lowering/src/item.rs

@@ -1,11 +1,11 @@
-use super::{AnonymousLifetimeMode, LoweringContext, ParamMode};
 use super::{AstOwner, ImplTraitContext, ImplTraitPosition, ResolverAstLowering};
+use super::{LoweringContext, ParamMode};
 use crate::{Arena, FnDeclKind};
 
 use rustc_ast::ptr::P;
 use rustc_ast::visit::AssocCtxt;
 use rustc_ast::*;
-use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::fx::FxHashMap;
 use rustc_data_structures::sorted_map::SortedMap;
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
@@ -81,13 +81,10 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             is_in_loop_condition: false,
             is_in_trait_impl: false,
             is_in_dyn_type: false,
-            anonymous_lifetime_mode: AnonymousLifetimeMode::PassThrough,
             generator_kind: None,
             task_context: None,
             current_item: None,
-            lifetimes_to_define: Vec::new(),
-            is_collecting_anonymous_lifetimes: None,
-            in_scope_lifetimes: Vec::new(),
+            captured_lifetimes: None,
             allow_try_trait: Some([sym::try_trait_v2][..].into()),
             allow_gen_future: Some([sym::gen_future][..].into()),
             allow_into_future: Some([sym::into_future][..].into()),
@@ -143,32 +140,14 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             LocalDefId { local_def_index }
         };
 
-        let parent_hir = self.lower_node(parent_id).unwrap().node().expect_item();
+        let parent_hir = self.lower_node(parent_id).unwrap();
         self.with_lctx(item.id, |lctx| {
             // Evaluate with the lifetimes in `params` in-scope.
             // This is used to track which lifetimes have already been defined,
             // and which need to be replicated when lowering an async fn.
-            match parent_hir.kind {
-                hir::ItemKind::Impl(hir::Impl { ref of_trait, ref generics, .. }) => {
+            match parent_hir.node().expect_item().kind {
+                hir::ItemKind::Impl(hir::Impl { ref of_trait, .. }) => {
                     lctx.is_in_trait_impl = of_trait.is_some();
-                    lctx.in_scope_lifetimes = generics
-                        .params
-                        .iter()
-                        .filter(|param| {
-                            matches!(param.kind, hir::GenericParamKind::Lifetime { .. })
-                        })
-                        .map(|param| param.name)
-                        .collect();
-                }
-                hir::ItemKind::Trait(_, _, ref generics, ..) => {
-                    lctx.in_scope_lifetimes = generics
-                        .params
-                        .iter()
-                        .filter(|param| {
-                            matches!(param.kind, hir::GenericParamKind::Lifetime { .. })
-                        })
-                        .map(|param| param.name)
-                        .collect();
                 }
                 _ => {}
             };
@@ -276,7 +255,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ref body,
                 ..
             }) => {
-                let fn_def_id = self.resolver.local_def_id(id);
                 self.with_new_scopes(|this| {
                     this.current_item = Some(ident.span);
 
@@ -288,20 +266,11 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     let body_id =
                         this.lower_maybe_async_body(span, &decl, asyncness, body.as_deref());
 
-                    let (generics, decl) = this.add_in_band_defs(
-                        generics,
-                        fn_def_id,
-                        AnonymousLifetimeMode::PassThrough,
-                        |this, idty| {
+                    let (generics, decl) =
+                        this.add_implicit_generics(generics, id, |this, idty| {
                             let ret_id = asyncness.opt_return_id();
-                            this.lower_fn_decl(
-                                &decl,
-                                Some((fn_def_id, idty)),
-                                FnDeclKind::Fn,
-                                ret_id,
-                            )
-                        },
-                    );
+                            this.lower_fn_decl(&decl, Some((id, idty)), FnDeclKind::Fn, ret_id)
+                        });
                     let sig = hir::FnSig {
                         decl,
                         header: this.lower_fn_header(header),
@@ -339,12 +308,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 //
                 // type Foo = Foo1
                 // opaque type Foo1: Trait
-                let ty = self.lower_ty(
-                    ty,
-                    ImplTraitContext::TypeAliasesOpaqueTy {
-                        capturable_lifetimes: &mut FxHashSet::default(),
-                    },
-                );
+                let ty = self.lower_ty(ty, ImplTraitContext::TypeAliasesOpaqueTy);
                 let mut generics = generics.clone();
                 add_ty_alias_where_clause(&mut generics, where_clauses, true);
                 let generics = self.lower_generics(
@@ -419,12 +383,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 // method, it will not be considered an in-band
                 // lifetime to be added, but rather a reference to a
                 // parent lifetime.
-                let lowered_trait_def_id = hir_id.expect_owner();
-                let (generics, (trait_ref, lowered_ty)) = self.add_in_band_defs(
-                    ast_generics,
-                    lowered_trait_def_id,
-                    AnonymousLifetimeMode::CreateParameter,
-                    |this, _| {
+                let (generics, (trait_ref, lowered_ty)) =
+                    self.add_implicit_generics(ast_generics, id, |this, _| {
                         let trait_ref = trait_ref.as_ref().map(|trait_ref| {
                             this.lower_trait_ref(
                                 trait_ref,
@@ -436,16 +396,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                             .lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type));
 
                         (trait_ref, lowered_ty)
-                    },
-                );
-
-                let new_impl_items =
-                    self.with_in_scope_lifetime_defs(&ast_generics.params, |this| {
-                        this.arena.alloc_from_iter(
-                            impl_items.iter().map(|item| this.lower_impl_item_ref(item)),
-                        )
                     });
 
+                let new_impl_items = self
+                    .arena
+                    .alloc_from_iter(impl_items.iter().map(|item| self.lower_impl_item_ref(item)));
+
                 // `defaultness.has_value()` is never called for an `impl`, always `true` in order
                 // to not cause an assertion failure inside the `lower_defaultness` function.
                 let has_val = true;
@@ -692,18 +648,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
             kind: match i.kind {
                 ForeignItemKind::Fn(box Fn { ref sig, ref generics, .. }) => {
                     let fdec = &sig.decl;
-                    let (generics, (fn_dec, fn_args)) = self.add_in_band_defs(
-                        generics,
-                        def_id,
-                        AnonymousLifetimeMode::PassThrough,
-                        |this, _| {
+                    let (generics, (fn_dec, fn_args)) =
+                        self.add_implicit_generics(generics, i.id, |this, _| {
                             (
                                 // Disallow `impl Trait` in foreign items.
                                 this.lower_fn_decl(fdec, None, FnDeclKind::ExternFn, None),
                                 this.lower_fn_params_to_names(fdec),
                             )
-                        },
-                    );
+                        });
 
                     hir::ForeignItemKind::Fn(fn_dec, fn_args, generics)
                 }
@@ -810,13 +762,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
             }
             AssocItemKind::Fn(box Fn { ref sig, ref generics, body: None, .. }) => {
                 let names = self.lower_fn_params_to_names(&sig.decl);
-                let (generics, sig) = self.lower_method_sig(
-                    generics,
-                    sig,
-                    trait_item_def_id,
-                    FnDeclKind::Trait,
-                    None,
-                );
+                let (generics, sig) =
+                    self.lower_method_sig(generics, sig, i.id, FnDeclKind::Trait, None);
                 (generics, hir::TraitItemKind::Fn(sig, hir::TraitFn::Required(names)))
             }
             AssocItemKind::Fn(box Fn { ref sig, ref generics, body: Some(ref body), .. }) => {
@@ -826,7 +773,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, sig) = self.lower_method_sig(
                     generics,
                     sig,
-                    trait_item_def_id,
+                    i.id,
                     FnDeclKind::Trait,
                     asyncness.opt_return_id(),
                 );
@@ -900,8 +847,6 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_impl_item(&mut self, i: &AssocItem) -> &'hir hir::ImplItem<'hir> {
-        let impl_item_def_id = self.resolver.local_def_id(i.id);
-
         let (generics, kind) = match &i.kind {
             AssocItemKind::Const(_, ty, expr) => {
                 let ty = self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type));
@@ -918,7 +863,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 let (generics, sig) = self.lower_method_sig(
                     generics,
                     sig,
-                    impl_item_def_id,
+                    i.id,
                     if self.is_in_trait_impl { FnDeclKind::Impl } else { FnDeclKind::Inherent },
                     asyncness.opt_return_id(),
                 );
@@ -938,12 +883,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                         hir::ImplItemKind::TyAlias(ty)
                     }
                     Some(ty) => {
-                        let ty = self.lower_ty(
-                            ty,
-                            ImplTraitContext::TypeAliasesOpaqueTy {
-                                capturable_lifetimes: &mut FxHashSet::default(),
-                            },
-                        );
+                        let ty = self.lower_ty(ty, ImplTraitContext::TypeAliasesOpaqueTy);
                         hir::ImplItemKind::TyAlias(ty)
                     }
                 };
@@ -1283,17 +1223,14 @@ impl<'hir> LoweringContext<'_, 'hir> {
         &mut self,
         generics: &Generics,
         sig: &FnSig,
-        fn_def_id: LocalDefId,
+        id: NodeId,
         kind: FnDeclKind,
         is_async: Option<NodeId>,
     ) -> (hir::Generics<'hir>, hir::FnSig<'hir>) {
         let header = self.lower_fn_header(sig.header);
-        let (generics, decl) = self.add_in_band_defs(
-            generics,
-            fn_def_id,
-            AnonymousLifetimeMode::PassThrough,
-            |this, idty| this.lower_fn_decl(&sig.decl, Some((fn_def_id, idty)), kind, is_async),
-        );
+        let (generics, decl) = self.add_implicit_generics(generics, id, |this, idty| {
+            this.lower_fn_decl(&sig.decl, Some((id, idty)), kind, is_async)
+        });
         (generics, hir::FnSig { header, decl, span: self.lower_span(sig.span) })
     }
 
@@ -1418,14 +1355,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
     }
 
     fn lower_where_clause(&mut self, wc: &WhereClause) -> hir::WhereClause<'hir> {
-        self.with_anonymous_lifetime_mode(AnonymousLifetimeMode::ReportError, |this| {
-            hir::WhereClause {
-                predicates: this.arena.alloc_from_iter(
-                    wc.predicates.iter().map(|predicate| this.lower_where_predicate(predicate)),
-                ),
-                span: this.lower_span(wc.span),
-            }
-        })
+        hir::WhereClause {
+            predicates: self.arena.alloc_from_iter(
+                wc.predicates.iter().map(|predicate| self.lower_where_predicate(predicate)),
+            ),
+            span: self.lower_span(wc.span),
+        }
     }
 
     fn lower_where_predicate(&mut self, pred: &WherePredicate) -> hir::WherePredicate<'hir> {
@@ -1435,24 +1370,20 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ref bounded_ty,
                 ref bounds,
                 span,
-            }) => self.with_in_scope_lifetime_defs(&bound_generic_params, |this| {
-                hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
-                    bound_generic_params: this.lower_generic_params(
-                        bound_generic_params,
-                        ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
-                    ),
-                    bounded_ty: this.lower_ty(
-                        bounded_ty,
-                        ImplTraitContext::Disallowed(ImplTraitPosition::Type),
-                    ),
-                    bounds: this.arena.alloc_from_iter(bounds.iter().map(|bound| {
-                        this.lower_param_bound(
-                            bound,
-                            ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
-                        )
-                    })),
-                    span: this.lower_span(span),
-                })
+            }) => hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
+                bound_generic_params: self.lower_generic_params(
+                    bound_generic_params,
+                    ImplTraitContext::Disallowed(ImplTraitPosition::Generic),
+                ),
+                bounded_ty: self
+                    .lower_ty(bounded_ty, ImplTraitContext::Disallowed(ImplTraitPosition::Type)),
+                bounds: self.arena.alloc_from_iter(bounds.iter().map(|bound| {
+                    self.lower_param_bound(
+                        bound,
+                        ImplTraitContext::Disallowed(ImplTraitPosition::Bound),
+                    )
+                })),
+                span: self.lower_span(span),
             }),
             WherePredicate::RegionPredicate(WhereRegionPredicate {
                 ref lifetime,