Refactor Pluralisation

Modify files performing pluralisation checks to incorporate the
dedicated macro located in `syntax::errors`.

src/librustc/ty/error.rs

@@ -4,6 +4,7 @@ use std::borrow::Cow;
 use std::fmt;
 use rustc_target::spec::abi;
 use syntax::ast;
+use syntax::errors::pluralise;
 use errors::{Applicability, DiagnosticBuilder};
 use syntax_pos::Span;
 
@@ -82,12 +83,6 @@ impl<'tcx> fmt::Display for TypeError<'tcx> {
             }
         };
 
-        macro_rules! pluralise {
-            ($x:expr) => {
-                if $x != 1 { "s" } else { "" }
-            };
-        }
-
         match *self {
             CyclicTy(_) => write!(f, "cyclic type of infinite size"),
             Mismatch => write!(f, "types differ"),

src/librustc_typeck/astconv.rs

@@ -23,6 +23,7 @@ use rustc_target::spec::abi;
 use crate::require_c_abi_if_c_variadic;
 use smallvec::SmallVec;
 use syntax::ast;
+use syntax::errors::pluralise;
 use syntax::feature_gate::{GateIssue, emit_feature_err};
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::symbol::sym;
@@ -377,7 +378,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     quantifier,
                     bound,
                     kind,
-                    if bound != 1 { "s" } else { "" },
+                    pluralise!(bound),
                 ))
             };
 

src/librustc_typeck/check/compare_method.rs

@@ -10,6 +10,7 @@ use rustc::util::common::ErrorReported;
 use errors::{Applicability, DiagnosticId};
 
 use syntax_pos::Span;
+use syntax::errors::pluralise;
 
 use super::{Inherited, FnCtxt, potentially_plural_count};
 
@@ -648,9 +649,9 @@ fn compare_number_of_generics<'tcx>(
                      declaration has {} {kind} parameter{}",
                     trait_.ident,
                     impl_count,
-                    if impl_count != 1 { "s" } else { "" },
+                    pluralise!(impl_count),
                     trait_count,
-                    if trait_count != 1 { "s" } else { "" },
+                    pluralise!(trait_count),
                     kind = kind,
                 ),
                 DiagnosticId::Error("E0049".into()),
@@ -665,7 +666,7 @@ fn compare_number_of_generics<'tcx>(
                         "expected {} {} parameter{}",
                         trait_count,
                         kind,
-                        if trait_count != 1 { "s" } else { "" },
+                        pluralise!(trait_count),
                     ));
                 }
                 for span in spans {
@@ -680,7 +681,7 @@ fn compare_number_of_generics<'tcx>(
                     "found {} {} parameter{}{}",
                     impl_count,
                     kind,
-                    if impl_count != 1 { "s" } else { "" },
+                    pluralise!(impl_count),
                     suffix.unwrap_or_else(|| String::new()),
                 ));
             }