Auto merge of #99867 - spastorino:refactor-remap-lifetimes, r=nikomatsakis

Split create_def and lowering of lifetimes for opaque types and bare async fns

r? `@cjgillot`

This work is kind of half-way, but I think it could be merged anyway.
I think we should be able to remove all the vacant arms in `new_named_lifetime_with_res`, if I'm not wrong that requires visiting more nodes. We can do that as a follow up.
In follow-up PRs, besides the thing mentioned previously, I'll be trying to remove `LifetimeCaptureContext`, `captured_lifetimes` as a global data structure, global `binders_to_ignore` and all their friends :).

Also try to remap in a more general way based on def-ids.

Author: bors

compiler/rustc_ast/src/ast.rs

@@ -64,7 +64,7 @@ impl fmt::Debug for Label {
 
 /// A "Lifetime" is an annotation of the scope in which variable
 /// can be used, e.g. `'a` in `&'a i32`.
-#[derive(Clone, Encodable, Decodable, Copy)]
+#[derive(Clone, Encodable, Decodable, Copy, PartialEq, Eq)]
 pub struct Lifetime {
     pub id: NodeId,
     pub ident: Ident,

compiler/rustc_ast_lowering/src/expr.rs

@@ -864,22 +864,21 @@ impl<'hir> LoweringContext<'_, 'hir> {
             (body_id, generator_option)
         });
 
-        self.with_lifetime_binder(closure_id, generic_params, |this, bound_generic_params| {
-            // Lower outside new scope to preserve `is_in_loop_condition`.
-            let fn_decl = this.lower_fn_decl(decl, None, FnDeclKind::Closure, None);
-
-            let c = self.arena.alloc(hir::Closure {
-                binder: binder_clause,
-                capture_clause,
-                bound_generic_params,
-                fn_decl,
-                body: body_id,
-                fn_decl_span: this.lower_span(fn_decl_span),
-                movability: generator_option,
-            });
+        let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params);
+        // Lower outside new scope to preserve `is_in_loop_condition`.
+        let fn_decl = self.lower_fn_decl(decl, None, FnDeclKind::Closure, None);
+
+        let c = self.arena.alloc(hir::Closure {
+            binder: binder_clause,
+            capture_clause,
+            bound_generic_params,
+            fn_decl,
+            body: body_id,
+            fn_decl_span: self.lower_span(fn_decl_span),
+            movability: generator_option,
+        });
 
-            hir::ExprKind::Closure(c)
-        })
+        hir::ExprKind::Closure(c)
     }
 
     fn generator_movability_for_fn(
@@ -991,23 +990,23 @@ impl<'hir> LoweringContext<'_, 'hir> {
             body_id
         });
 
-        self.with_lifetime_binder(closure_id, generic_params, |this, bound_generic_params| {
-            // We need to lower the declaration outside the new scope, because we
-            // have to conserve the state of being inside a loop condition for the
-            // closure argument types.
-            let fn_decl = this.lower_fn_decl(&outer_decl, None, FnDeclKind::Closure, None);
-
-            let c = self.arena.alloc(hir::Closure {
-                binder: binder_clause,
-                capture_clause,
-                bound_generic_params,
-                fn_decl,
-                body,
-                fn_decl_span: this.lower_span(fn_decl_span),
-                movability: None,
-            });
-            hir::ExprKind::Closure(c)
-        })
+        let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params);
+
+        // We need to lower the declaration outside the new scope, because we
+        // have to conserve the state of being inside a loop condition for the
+        // closure argument types.
+        let fn_decl = self.lower_fn_decl(&outer_decl, None, FnDeclKind::Closure, None);
+
+        let c = self.arena.alloc(hir::Closure {
+            binder: binder_clause,
+            capture_clause,
+            bound_generic_params,
+            fn_decl,
+            body,
+            fn_decl_span: self.lower_span(fn_decl_span),
+            movability: None,
+        });
+        hir::ExprKind::Closure(c)
     }
 
     /// Destructure the LHS of complex assignments.

compiler/rustc_ast_lowering/src/item.rs

@@ -80,7 +80,6 @@ impl<'a, 'hir> ItemLowerer<'a, 'hir> {
             generator_kind: None,
             task_context: None,
             current_item: None,
-            captured_lifetimes: None,
             impl_trait_defs: Vec::new(),
             impl_trait_bounds: Vec::new(),
             allow_try_trait: Some([sym::try_trait_v2, sym::yeet_desugar_details][..].into()),
@@ -1350,12 +1349,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
 
         let mut predicates: SmallVec<[hir::WherePredicate<'hir>; 4]> = SmallVec::new();
         predicates.extend(generics.params.iter().filter_map(|param| {
-            let bounds = self.lower_param_bounds(&param.bounds, itctx);
             self.lower_generic_bound_predicate(
                 param.ident,
                 param.id,
                 &param.kind,
-                bounds,
+                &param.bounds,
+                itctx,
                 PredicateOrigin::GenericParam,
             )
         }));
@@ -1403,13 +1402,17 @@ impl<'hir> LoweringContext<'_, 'hir> {
         ident: Ident,
         id: NodeId,
         kind: &GenericParamKind,
-        bounds: &'hir [hir::GenericBound<'hir>],
+        bounds: &[GenericBound],
+        itctx: ImplTraitContext,
         origin: PredicateOrigin,
     ) -> Option<hir::WherePredicate<'hir>> {
         // Do not create a clause if we do not have anything inside it.
         if bounds.is_empty() {
             return None;
         }
+
+        let bounds = self.lower_param_bounds(bounds, itctx);
+
         let ident = self.lower_ident(ident);
         let param_span = ident.span;
         let span = bounds
@@ -1450,11 +1453,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
             GenericParamKind::Lifetime => {
                 let ident_span = self.lower_span(ident.span);
                 let ident = self.lower_ident(ident);
-                let res = self.resolver.get_lifetime_res(id).unwrap_or_else(|| {
-                    panic!("Missing resolution for lifetime {:?} at {:?}", id, ident.span)
-                });
                 let lt_id = self.next_node_id();
-                let lifetime = self.new_named_lifetime_with_res(lt_id, ident_span, ident, res);
+                let lifetime = self.new_named_lifetime(id, lt_id, ident_span, ident);
                 Some(hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
                     lifetime,
                     span,