Remove `TraitDef::attributes`.

Because it's always empty.

compiler/rustc_builtin_macros/src/deriving/bounds.rs

@@ -15,7 +15,6 @@ pub fn expand_deriving_copy(
 ) {
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: path_std!(marker::Copy),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/clone.rs

@@ -71,7 +71,6 @@ pub fn expand_deriving_clone(
     let attrs = vec![cx.attribute(inline)];
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: path_std!(clone::Clone),
         additional_bounds: bounds,
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/cmp/eq.rs

@@ -23,7 +23,6 @@ pub fn expand_deriving_eq(
     let attrs = vec![cx.attribute(inline), cx.attribute(doc), cx.attribute(no_coverage)];
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: path_std!(cmp::Eq),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/cmp/ord.rs

@@ -18,7 +18,6 @@ pub fn expand_deriving_ord(
     let attrs = vec![cx.attribute(inline)];
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: path_std!(cmp::Ord),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -98,7 +98,6 @@ pub fn expand_deriving_partial_eq(
 
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: path_std!(cmp::PartialEq),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/cmp/partial_ord.rs

@@ -36,7 +36,6 @@ pub fn expand_deriving_partial_ord(
 
     let trait_def = TraitDef {
         span,
-        attributes: vec![],
         path: path_std!(cmp::PartialOrd),
         additional_bounds: vec![],
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/debug.rs

@@ -19,7 +19,6 @@ pub fn expand_deriving_debug(
 
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: path_std!(fmt::Debug),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/decodable.rs

@@ -22,7 +22,6 @@ pub fn expand_deriving_rustc_decodable(
 
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: Path::new_(vec![krate, sym::Decodable], vec![], PathKind::Global),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/default.rs

@@ -25,7 +25,6 @@ pub fn expand_deriving_default(
     let attrs = vec![cx.attribute(inline)];
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: Path::new(vec![kw::Default, sym::Default]),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/encodable.rs

@@ -106,7 +106,6 @@ pub fn expand_deriving_rustc_encodable(
 
     let trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path: Path::new_(vec![krate, sym::Encodable], vec![], PathKind::Global),
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -184,8 +184,6 @@ pub struct TraitDef<'a> {
     /// The span for the current #[derive(Foo)] header.
     pub span: Span,
 
-    pub attributes: Vec<ast::Attribute>,
-
     /// Path of the trait, including any type parameters
     pub path: Path,
 
@@ -718,15 +716,13 @@ impl<'a> TraitDef<'a> {
         let self_type = cx.ty_path(path);
 
         let attr = cx.attribute(cx.meta_word(self.span, sym::automatically_derived));
+        let attrs = vec![attr];
         let opt_trait_ref = Some(trait_ref);
 
-        let mut a = vec![attr];
-        a.extend(self.attributes.iter().cloned());
-
         cx.item(
             self.span,
             Ident::empty(),
-            a,
+            attrs,
             ast::ItemKind::Impl(Box::new(ast::Impl {
                 unsafety: ast::Unsafe::No,
                 polarity: ast::ImplPolarity::Positive,

compiler/rustc_builtin_macros/src/deriving/hash.rs

@@ -21,7 +21,6 @@ pub fn expand_deriving_hash(
     let arg = Path::new_local(typaram);
     let hash_trait_def = TraitDef {
         span,
-        attributes: Vec::new(),
         path,
         additional_bounds: Vec::new(),
         generics: Bounds::empty(),