Compute item_generics_num_lifetimes during resolution.

compiler/rustc_resolve/src/late.rs

@@ -952,6 +952,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
         match item.kind {
             ItemKind::TyAlias(box TyAliasKind(_, ref generics, _, _))
             | ItemKind::Fn(box FnKind(_, _, ref generics, _)) => {
+                self.compute_num_lifetime_params(item.id, generics);
                 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
                     visit::walk_item(this, item)
                 });
@@ -960,6 +961,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             ItemKind::Enum(_, ref generics)
             | ItemKind::Struct(_, ref generics)
             | ItemKind::Union(_, ref generics) => {
+                self.compute_num_lifetime_params(item.id, generics);
                 self.resolve_adt(item, generics);
             }
 
@@ -970,10 +972,12 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
                 items: ref impl_items,
                 ..
             }) => {
+                self.compute_num_lifetime_params(item.id, generics);
                 self.resolve_implementation(generics, of_trait, &self_ty, item.id, impl_items);
             }
 
             ItemKind::Trait(box TraitKind(.., ref generics, ref bounds, ref trait_items)) => {
+                self.compute_num_lifetime_params(item.id, generics);
                 // Create a new rib for the trait-wide type parameters.
                 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
                     let local_def_id = this.r.local_def_id(item.id).to_def_id();
@@ -1025,6 +1029,7 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             }
 
             ItemKind::TraitAlias(ref generics, ref bounds) => {
+                self.compute_num_lifetime_params(item.id, generics);
                 // Create a new rib for the trait-wide type parameters.
                 self.with_generic_param_rib(generics, ItemRibKind(HasGenericParams::Yes), |this| {
                     let local_def_id = this.r.local_def_id(item.id).to_def_id();
@@ -2463,6 +2468,16 @@ impl<'a: 'ast, 'b, 'ast> LateResolutionVisitor<'a, 'b, 'ast> {
             Some((ident.name, ns)),
         )
     }
+
+    fn compute_num_lifetime_params(&mut self, id: NodeId, generics: &Generics) {
+        let def_id = self.r.local_def_id(id);
+        let count = generics
+            .params
+            .iter()
+            .filter(|param| matches!(param.kind, ast::GenericParamKind::Lifetime { .. }))
+            .count();
+        self.r.item_generics_num_lifetimes.insert(def_id, count);
+    }
 }
 
 impl<'a> Resolver<'a> {