Tweak wording on "other methods available" note

Handle correct gramar in the face of a single other option, or many.

Author: estebank

compiler/rustc_hir_typeck/src/demand.rs

@@ -1,4 +1,4 @@
-use rustc_errors::{Applicability, Diag, MultiSpan, listify};
+use rustc_errors::{Applicability, Diag, MultiSpan, listify, pluralize};
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::intravisit::Visitor;
 use rustc_hir::{self as hir, find_attr};
@@ -1072,9 +1072,11 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             ),
         );
         if suggestions.len() > other_methods_in_scope.len() {
+            let n = suggestions.len() - other_methods_in_scope.len();
             err.note(format!(
-                "additionally, there are {} other available methods that aren't in scope",
-                suggestions.len() - other_methods_in_scope.len()
+                "additionally, there {are} {n} other available method{s} that {are}n't in scope",
+                are = pluralize!("is", n),
+                s = pluralize!(n),
             ));
         }
         err.multipart_suggestions(

tests/ui/mismatched_types/diagnostic-method-lookup-returns-sig-with-fewer-args.stderr

@@ -16,7 +16,7 @@ note: the `get` call is resolved to the method in `Target`, shadowing the method
    |
 LL |     target.get(10.0); // (used to crash here)
    |            ^^^ refers to `Target::get`
-   = note: additionally, there are 1 other available methods that aren't in scope
+   = note: additionally, there is 1 other available method that isn't in scope
 help: you might have meant to call one of the other methods; you can use the fully-qualified path to call one of them explicitly
    |
 LL -     target.get(10.0); // (used to crash here)