Auto merge of #34842 - cgswords:attr_enc, r=nrc

Better attribute and metaitem encapsulation throughout the compiler

This PR refactors most (hopefully all?) of the `MetaItem` interactions outside of `libsyntax` (and a few inside) to interact with MetaItems through the provided traits instead of directly creating / destruct / matching against them. This is a necessary first step to eventually converting `MetaItem`s to internally use `TokenStream` representations (which will make `MetaItem` interactions much nicer for macro writers once the new macro system is in place).

r? @nrc

2 files changed, 8 insertions, 20 deletions

diff --git a/src/libsyntax/ext/build.rs b/src/libsyntax/ext/build.rs
index 435241f426e..5d6429f7bdf 100644
--- a/src/libsyntax/ext/build.rs
+++ b/src/libsyntax/ext/build.rs
@@ -1135,30 +1135,19 @@ impl<'a> AstBuilder for ExtCtxt<'a> {
     }
 
     fn attribute(&self, sp: Span, mi: P<ast::MetaItem>) -> ast::Attribute {
-        respan(sp, ast::Attribute_ {
-            id: attr::mk_attr_id(),
-            style: ast::AttrStyle::Outer,
-            value: mi,
-            is_sugared_doc: false,
-        })
+        attr::mk_spanned_attr_outer(sp, attr::mk_attr_id(), mi)
     }
 
     fn meta_word(&self, sp: Span, w: InternedString) -> P<ast::MetaItem> {
-        P(respan(sp, ast::MetaItemKind::Word(w)))
+        attr::mk_spanned_word_item(sp, w)
     }
-    fn meta_list(&self,
-                 sp: Span,
-                 name: InternedString,
-                 mis: Vec<P<ast::MetaItem>> )
+    fn meta_list(&self, sp: Span, name: InternedString, mis: Vec<P<ast::MetaItem>>)
                  -> P<ast::MetaItem> {
-        P(respan(sp, ast::MetaItemKind::List(name, mis)))
+        attr::mk_spanned_list_item(sp, name, mis)
     }
-    fn meta_name_value(&self,
-                       sp: Span,
-                       name: InternedString,
-                       value: ast::LitKind)
+    fn meta_name_value(&self, sp: Span, name: InternedString, value: ast::LitKind)
                        -> P<ast::MetaItem> {
-        P(respan(sp, ast::MetaItemKind::NameValue(name, respan(sp, value))))
+        attr::mk_spanned_name_value_item(sp, name, respan(sp, value))
     }
 
     fn item_use(&self, sp: Span,
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 18342f2e38c..5293d2ab000 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -302,9 +302,8 @@ fn contains_macro_use(fld: &mut MacroExpander, attrs: &[ast::Attribute]) -> bool
         };
 
         if is_use {
-            match attr.node.value.node {
-                ast::MetaItemKind::Word(..) => (),
-                _ => fld.cx.span_err(attr.span, "arguments to macro_use are not allowed here"),
+            if !attr.is_word() {
+              fld.cx.span_err(attr.span, "arguments to macro_use are not allowed here");
             }
             return true;
         }