Revert the message as before if number of input or expected arguments is one

Author: long-long-float

compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs

@@ -1068,7 +1068,15 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                     } else {
                         "".to_string()
                     };
-                    labels.push((provided_span, format!("unexpected {} argument{provided_ty_name}", ordinalize(arg_idx.as_usize() + 1))));
+                    let ord = if provided_arg_tys.len() == 1 {
+                        "".to_string()
+                    } else {
+                        format!("{} ", ordinalize(arg_idx.as_usize() + 1))
+                    };
+                    labels.push((
+                        provided_span,
+                        format!("unexpected {ord}argument{provided_ty_name}"),
+                    ));
                     let mut span = provided_span;
                     if span.can_be_used_for_suggestions()
                         && error_span.can_be_used_for_suggestions()
@@ -1149,7 +1157,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                             } else {
                                 "".to_string()
                             };
-                            labels.push((span, format!("{} argument{rendered} is missing", ordinalize(expected_idx.as_usize() + 1))));
+                            let ord = if formal_and_expected_inputs.len() == 1 {
+                                "an".to_string()
+                            } else {
+                                ordinalize(expected_idx.as_usize() + 1)
+                            };
+                            labels.push((span, format!("{ord} argument{rendered} is missing")));
 
                             suggestion_text = match suggestion_text {
                                 SuggestionText::None => SuggestionText::Provide(false),