Rollup merge of #64342 - glorv:master, r=varkor

factor out pluralisation remains after #64280

there are two case that doesn't not match the original macro pattern at [here](https://github.com/rust-lang/rust/blob/master/src/librustc_lint/unused.rs#L146) and [here](https://github.com/rust-lang/rust/blob/master/src/libsyntax/parse/diagnostics.rs#L539) as the provided param is already a bool or the check condition is not `x != 1`, so I change the macro accept a boolean expr instead of number to fit all the cases.

@Centril  please review

Fixes #64238.

1 files changed, 2 insertions, 1 deletions

diff --git a/src/libsyntax_ext/format.rs b/src/libsyntax_ext/format.rs
index 46c7cbb83de..26455df17b8 100644
--- a/src/libsyntax_ext/format.rs
+++ b/src/libsyntax_ext/format.rs
@@ -5,6 +5,7 @@ use fmt_macros as parse;
 
 use errors::DiagnosticBuilder;
 use errors::Applicability;
+use errors::pluralise;
 
 use syntax::ast;
 use syntax::ext::base::{self, *};
@@ -299,7 +300,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 &format!(
                     "{} positional argument{} in format string, but {}",
                     count,
-                    if count != 1 { "s" } else { "" },
+                    pluralise!(count),
                     self.describe_num_args(),
                 ),
             );