Remove attrs arg from typaram and mk_ty_param.

Because it's always empty.

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

@@ -603,7 +603,7 @@ fn create_derived_impl(
                         param.bounds.iter().cloned()
                     ).collect();
 
-                cx.typaram(param.ident.span.with_ctxt(ctxt), param.ident, vec![], bounds, None)
+                cx.typaram(param.ident.span.with_ctxt(ctxt), param.ident, bounds, None)
             }
             GenericParamKind::Const { ty, kw_span, .. } => {
                 let const_nodefault_kind = GenericParamKind::Const {

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

@@ -146,7 +146,6 @@ fn mk_ty_param(
     cx: &ExtCtxt<'_>,
     span: Span,
     name: Symbol,
-    attrs: &[ast::Attribute],
     bounds: &[Path],
     self_ident: Ident,
     self_generics: &Generics,
@@ -158,7 +157,7 @@ fn mk_ty_param(
             cx.trait_bound(path)
         })
         .collect();
-    cx.typaram(span, Ident::new(name, span), attrs.to_owned(), bounds, None)
+    cx.typaram(span, Ident::new(name, span), bounds, None)
 }
 
 /// Bounds on type parameters.
@@ -183,7 +182,7 @@ pub fn to_generics(
             .iter()
             .map(|t| {
                 let (name, ref bounds) = *t;
-                mk_ty_param(cx, span, name, &[], &bounds, self_ty, self_generics)
+                mk_ty_param(cx, span, name, &bounds, self_ty, self_generics)
             })
             .collect();
 

compiler/rustc_expand/src/build.rs

@@ -106,14 +106,13 @@ pub fn typaram(
         &self,
         span: Span,
         ident: Ident,
-        attrs: Vec<ast::Attribute>,
         bounds: ast::GenericBounds,
         default: Option<P<ast::Ty>>,
     ) -> ast::GenericParam {
         ast::GenericParam {
             ident: ident.with_span_pos(span),
             id: ast::DUMMY_NODE_ID,
-            attrs: attrs.into(),
+            attrs: AttrVec::new(),
             bounds,
             kind: ast::GenericParamKind::Type { default },
             is_placeholder: false,