Avoid unnecessary `MetaItem`/`Attribute` conversions.

`check_builtin_attribute` calls `parse_meta` to convert an `Attribute`
to a `MetaItem`, which it then checks. However, many callers of
`check_builtin_attribute` start with a `MetaItem`, and then convert it
to an `Attribute` by calling `cx.attribute(meta_item)`. This `MetaItem`
to `Attribute` to `MetaItem` conversion is silly.

This commit adds a new function `check_builtin_meta_item`, which can be
called instead from these call sites. `check_builtin_attribute` also now
calls it. The commit also renames `check_meta` as `check_attr` to better
match its arguments.

1 files changed, 5 insertions, 4 deletions

diff --git a/compiler/rustc_builtin_macros/src/derive.rs b/compiler/rustc_builtin_macros/src/derive.rs
index c8a2fca00e8..0358c0b1b5f 100644
--- a/compiler/rustc_builtin_macros/src/derive.rs
+++ b/compiler/rustc_builtin_macros/src/derive.rs
@@ -33,14 +33,15 @@ impl MultiItemModifier for Expander {
             ecx.resolver.resolve_derives(ecx.current_expansion.id, ecx.force_mode, &|| {
                 let template =
                     AttributeTemplate { list: Some("Trait1, Trait2, ..."), ..Default::default() };
-                let attr =
-                    attr::mk_attr_outer(&sess.parse_sess.attr_id_generator, meta_item.clone());
-                validate_attr::check_builtin_attribute(
+                validate_attr::check_builtin_meta_item(
                     &sess.parse_sess,
-                    &attr,
+                    &meta_item,
+                    ast::AttrStyle::Outer,
                     sym::derive,
                     template,
                 );
+                let attr =
+                    attr::mk_attr_outer(&sess.parse_sess.attr_id_generator, meta_item.clone());
 
                 let mut resolutions: Vec<_> = attr
                     .meta_item_list()