Add and use generics.is_empty() and generics.is_own_empty, rather than using generics' attributes

compiler/rustc_middle/src/ty/generics.rs

@@ -391,6 +391,14 @@ impl<'tcx> Generics {
         }
         false
     }
+
+    pub fn is_empty(&'tcx self) -> bool {
+        self.count() == 0
+    }
+
+    pub fn is_own_empty(&'tcx self) -> bool {
+        self.own_params.is_empty()
+    }
 }
 
 /// Bounds on generics.

compiler/rustc_middle/src/ty/print/mod.rs

@@ -160,7 +160,7 @@ pub trait Printer<'tcx>: Sized {
                         // If we have any generic arguments to print, we do that
                         // on top of the same path, but without its own generics.
                         _ => {
-                            if !generics.own_params.is_empty() && args.len() >= generics.count() {
+                            if !generics.is_own_empty() && args.len() >= generics.count() {
                                 let args = generics.own_args_no_defaults(self.tcx(), args);
                                 return self.path_generic_args(
                                     |cx| cx.print_def_path(def_id, parent_args),