Correct pluralisation of various diagnostic messages

src/librustc/ty/error.rs

@@ -200,7 +200,9 @@ impl<'tcx> ty::TyS<'tcx> {
             ty::Array(_, n) => {
                 let n = tcx.lift_to_global(&n).unwrap();
                 match n.try_eval_usize(tcx, ty::ParamEnv::empty()) {
-                    Some(n) => format!("array of {} elements", n).into(),
+                    Some(n) => {
+                        format!("array of {} element{}", n, if n != 1 { "s" } else { "" }).into()
+                    }
                     None => "array".into(),
                 }
             }

src/librustc_typeck/check/pat.rs

@@ -1098,22 +1098,35 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
     fn error_scrutinee_inconsistent_length(&self, span: Span, min_len: u64, size: u64) {
         struct_span_err!(
-            self.tcx.sess, span, E0527,
-            "pattern requires {} elements but array has {}",
-            min_len, size
+            self.tcx.sess,
+            span,
+            E0527,
+            "pattern requires {} element{} but array has {}",
+            min_len,
+            if min_len != 1 { "s" } else { "" },
+            size,
         )
-        .span_label(span, format!("expected {} elements", size))
+        .span_label(span, format!("expected {} element{}", size, if size != 1 { "s" } else { "" }))
         .emit();
     }
 
     fn error_scrutinee_with_rest_inconsistent_length(&self, span: Span, min_len: u64, size: u64) {
         struct_span_err!(
-            self.tcx.sess, span, E0528,
-            "pattern requires at least {} elements but array has {}",
-            min_len, size
-        )
-        .span_label(span, format!("pattern cannot match array of {} elements", size))
-        .emit();
+            self.tcx.sess,
+            span,
+            E0528,
+            "pattern requires at least {} element{} but array has {}",
+            min_len,
+            if min_len != 1 { "s" } else { "" },
+            size,
+        ).span_label(
+            span,
+            format!(
+                "pattern cannot match array of {} element{}",
+                size,
+                if size != 1 { "s" } else { "" },
+            ),
+        ).emit();
     }
 
     fn error_scrutinee_unfixed_length(&self, span: Span) {

src/libsyntax/ext/tt/transcribe.rs

@@ -345,8 +345,13 @@ impl LockstepIterSize {
                 LockstepIterSize::Constraint(r_len, _) if l_len == r_len => self,
                 LockstepIterSize::Constraint(r_len, r_id) => {
                     let msg = format!(
-                        "meta-variable `{}` repeats {} times, but `{}` repeats {} times",
-                        l_id, l_len, r_id, r_len
+                        "meta-variable `{}` repeats {} time{}, but `{}` repeats {} time{}",
+                        l_id,
+                        l_len,
+                        if l_len != 1 { "s" } else { "" },
+                        r_id,
+                        r_len,
+                        if r_len != 1 { "s" } else { "" },
                     );
                     LockstepIterSize::Contradiction(msg)
                 }

src/libsyntax_ext/format.rs

@@ -291,7 +291,7 @@ impl<'a, 'b> Context<'a, 'b> {
                 &format!(
                     "{} positional argument{} in format string, but {}",
                     count,
-                    if count > 1 { "s" } else { "" },
+                    if count != 1 { "s" } else { "" },
                     self.describe_num_args(),
                 ),
             );