Capture lifetimes for associated type bounds destined to be lowered to opaques

Author: compiler-errors

compiler/rustc_ast_lowering/src/lib.rs

@@ -153,6 +153,7 @@ trait ResolverAstLoweringExt {
     fn get_label_res(&self, id: NodeId) -> Option<NodeId>;
     fn get_lifetime_res(&self, id: NodeId) -> Option<LifetimeRes>;
     fn take_extra_lifetime_params(&mut self, id: NodeId) -> Vec<(Ident, NodeId, LifetimeRes)>;
+    fn remap_extra_lifetime_params(&mut self, from: NodeId, to: NodeId);
     fn decl_macro_kind(&self, def_id: LocalDefId) -> MacroKind;
 }
 
@@ -213,6 +214,11 @@ impl ResolverAstLoweringExt for ResolverAstLowering {
         self.extra_lifetime_params_map.remove(&id).unwrap_or_default()
     }
 
+    fn remap_extra_lifetime_params(&mut self, from: NodeId, to: NodeId) {
+        let lifetimes = self.extra_lifetime_params_map.remove(&from).unwrap_or_default();
+        self.extra_lifetime_params_map.insert(to, lifetimes);
+    }
+
     fn decl_macro_kind(&self, def_id: LocalDefId) -> MacroKind {
         self.builtin_macro_kinds.get(&def_id).copied().unwrap_or(MacroKind::Bang)
     }
@@ -1089,6 +1095,11 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                         // constructing the HIR for `impl bounds...` and then lowering that.
 
                         let impl_trait_node_id = self.next_node_id();
+                        // Shift `impl Trait` lifetime captures from the associated type bound's
+                        // node id to the opaque node id, so that the opaque can actually use
+                        // these lifetime bounds.
+                        self.resolver
+                            .remap_extra_lifetime_params(constraint.id, impl_trait_node_id);
 
                         self.with_dyn_type_scope(false, |this| {
                             let node_id = this.next_node_id();

compiler/rustc_resolve/src/late.rs

@@ -1109,6 +1109,7 @@ impl<'a: 'ast, 'ast, 'tcx> Visitor<'ast> for LateResolutionVisitor<'a, '_, 'ast,
                 }
             },
             AssocConstraintKind::Bound { ref bounds } => {
+                self.record_lifetime_params_for_impl_trait(constraint.id);
                 walk_list!(self, visit_param_bound, bounds, BoundKind::Bound);
             }
         }

tests/ui/impl-trait/in-trait/lifetime-in-associated-trait-bound.rs

@@ -0,0 +1,19 @@
+// check-pass
+
+#![feature(associated_type_bounds, return_position_impl_trait_in_trait)]
+
+trait Trait {
+    type Type;
+
+    fn method(&self) -> impl Trait<Type: '_>;
+}
+
+impl Trait for () {
+    type Type = ();
+
+    fn method(&self) -> impl Trait<Type: '_> {
+        ()
+    }
+}
+
+fn main() {}