Fix warnings about the rustfmt_skip attribute

src/lib.rs

@@ -87,9 +87,8 @@ mod reexport {
     pub use syntax::ast::{Name, NodeId};
 }
 
-#[allow(unused_attributes)]
 #[plugin_registrar]
-#[rustfmt_skip]
+#[cfg_attr(rustfmt, rustfmt_skip)]
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box types::TypePass);
     reg.register_late_lint_pass(box misc::TopLevelRefPass);

src/methods.rs

@@ -736,7 +736,7 @@ fn has_debug_impl<'a, 'b>(ty: ty::Ty<'a>, cx: &LateContext<'b, 'a>) -> bool {
     debug_impl_exists
 }
 
-#[rustfmt_skip]
+#[cfg_attr(rustfmt, rustfmt_skip)]
 const CONVENTIONS: [(&'static str, &'static [SelfKind]); 5] = [
     ("into_", &[SelfKind::Value]),
     ("to_", &[SelfKind::Ref]),
@@ -745,7 +745,7 @@ const CONVENTIONS: [(&'static str, &'static [SelfKind]); 5] = [
     ("from_", &[SelfKind::No]),
 ];
 
-#[rustfmt_skip]
+#[cfg_attr(rustfmt, rustfmt_skip)]
 const TRAIT_METHODS: [(&'static str, usize, SelfKind, OutType, &'static str); 30] = [
     ("add", 2, SelfKind::Value, OutType::Any, "std::ops::Add"),
     ("sub", 2, SelfKind::Value, OutType::Any, "std::ops::Sub"),

src/misc.rs

@@ -376,8 +376,7 @@ impl LintPass for UsedUnderscoreBinding {
 }
 
 impl LateLintPass for UsedUnderscoreBinding {
-    #[allow(unused_attributes)]
-    #[rustfmt_skip]
+    #[cfg_attr(rustfmt, rustfmt_skip)]
     fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
         if in_attributes_expansion(cx, expr) {
     // Don't lint things expanded by #[derive(...)], etc