review comments

src/librustc_infer/infer/error_reporting/nice_region_error/named_anon_conflict.rs

@@ -92,9 +92,10 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                         .next()
                         .is_some()
                 {
+                    // If the failure is due to a `'static` requirement coming from a `dyn` or
+                    // `impl` Trait that *isn't* caused by `async fn` desugaring, handle this case
+                    // better in `static_impl_trait`.
                     debug!("try_report_named_anon_conflict: impl Trait + 'static");
-                    // This is an `impl Trait` or `dyn Trait` return that evaluates de need of
-                    // `'static`. We handle this case better in `static_impl_trait`.
                     return None;
                 }
             }

src/librustc_infer/infer/error_reporting/nice_region_error/static_impl_trait.rs

@@ -26,7 +26,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
                 );
                 let anon_reg_sup = self.tcx().is_suitable_region(sup_r)?;
                 debug!("try_report_static_impl_trait: anon_reg_sup={:?}", anon_reg_sup);
-                let fn_returns = self.tcx().return_type_impl_or_dyn_trait(anon_reg_sup.def_id);
+                let fn_returns = self.tcx().return_type_impl_or_dyn_traits(anon_reg_sup.def_id);
                 if fn_returns.is_empty() {
                     return None;
                 }

src/librustc_middle/ty/context.rs

@@ -1406,7 +1406,8 @@ impl<'tcx> TyCtxt<'tcx> {
         })
     }
 
-    pub fn return_type_impl_or_dyn_trait(&self, scope_def_id: DefId) -> Vec<&'tcx hir::Ty<'tcx>> {
+    /// Given a `DefId` for an `fn`, return all the `dyn` and `impl` traits in its return type.
+    pub fn return_type_impl_or_dyn_traits(&self, scope_def_id: DefId) -> Vec<&'tcx hir::Ty<'tcx>> {
         let hir_id = self.hir().as_local_hir_id(scope_def_id.expect_local());
         let hir_output = match self.hir().get(hir_id) {
             Node::Item(hir::Item {