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.

3 files changed, 16 insertions, 10 deletions

diff --git a/compiler/rustc_builtin_macros/src/cfg_accessible.rs b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
index 86df3c44eb3..4e4cafc7182 100644
--- a/compiler/rustc_builtin_macros/src/cfg_accessible.rs
+++ b/compiler/rustc_builtin_macros/src/cfg_accessible.rs
@@ -37,10 +37,10 @@ impl MultiItemModifier for Expander {
         _is_derive_const: bool,
     ) -> ExpandResult<Vec<Annotatable>, Annotatable> {
         let template = AttributeTemplate { list: Some("path"), ..Default::default() };
-        let attr = &ecx.attribute(meta_item.clone());
-        validate_attr::check_builtin_attribute(
+        validate_attr::check_builtin_meta_item(
             &ecx.sess.parse_sess,
-            attr,
+            &meta_item,
+            ast::AttrStyle::Outer,
             sym::cfg_accessible,
             template,
         );
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()
diff --git a/compiler/rustc_builtin_macros/src/util.rs b/compiler/rustc_builtin_macros/src/util.rs
index 527fe50eff0..83812631c2f 100644
--- a/compiler/rustc_builtin_macros/src/util.rs
+++ b/compiler/rustc_builtin_macros/src/util.rs
@@ -1,4 +1,4 @@
-use rustc_ast::{Attribute, MetaItem};
+use rustc_ast::{AttrStyle, Attribute, MetaItem};
 use rustc_expand::base::{Annotatable, ExtCtxt};
 use rustc_feature::AttributeTemplate;
 use rustc_lint_defs::builtin::DUPLICATE_MACRO_ATTRIBUTES;
@@ -8,8 +8,13 @@ use rustc_span::Symbol;
 pub fn check_builtin_macro_attribute(ecx: &ExtCtxt<'_>, meta_item: &MetaItem, name: Symbol) {
     // All the built-in macro attributes are "words" at the moment.
     let template = AttributeTemplate { word: true, ..Default::default() };
-    let attr = ecx.attribute(meta_item.clone());
-    validate_attr::check_builtin_attribute(&ecx.sess.parse_sess, &attr, name, template);
+    validate_attr::check_builtin_meta_item(
+        &ecx.sess.parse_sess,
+        &meta_item,
+        AttrStyle::Outer,
+        name,
+        template,
+    );
 }
 
 /// Emit a warning if the item is annotated with the given attribute. This is used to diagnose when