Rework Attribute::get_tokens.

Returning `Vec<TokenTree>` works better for the call sites than
returning `TokenStream`.

Author: nnethercote

compiler/rustc_ast/src/attr/mod.rs

@@ -202,21 +202,18 @@ impl Attribute {
         }
     }
 
-    // Named `get_tokens` to distinguish it from the `<Attribute as HasTokens>::tokens` method.
-    pub fn get_tokens(&self) -> TokenStream {
-        match &self.kind {
-            AttrKind::Normal(normal) => TokenStream::new(
-                normal
-                    .tokens
-                    .as_ref()
-                    .unwrap_or_else(|| panic!("attribute is missing tokens: {self:?}"))
-                    .to_attr_token_stream()
-                    .to_token_trees(),
-            ),
-            &AttrKind::DocComment(comment_kind, data) => TokenStream::token_alone(
+    pub fn token_trees(&self) -> Vec<TokenTree> {
+        match self.kind {
+            AttrKind::Normal(ref normal) => normal
+                .tokens
+                .as_ref()
+                .unwrap_or_else(|| panic!("attribute is missing tokens: {self:?}"))
+                .to_attr_token_stream()
+                .to_token_trees(),
+            AttrKind::DocComment(comment_kind, data) => vec![TokenTree::token_alone(
                 token::DocComment(comment_kind, self.style, data),
                 self.span,
-            ),
+            )],
         }
     }
 }

compiler/rustc_ast/src/tokenstream.rs

@@ -225,11 +225,12 @@ impl AttrTokenStream {
                                 // properly implemented - we always synthesize fake tokens,
                                 // so we never reach this code.
 
-                                let mut stream = TokenStream::default();
+                                let mut tts = vec![];
                                 for inner_attr in inner_attrs {
-                                    stream.push_stream(inner_attr.get_tokens());
+                                    tts.extend(inner_attr.token_trees());
                                 }
-                                stream.push_stream(delim_tokens.clone());
+                                tts.extend(delim_tokens.0.iter().cloned());
+                                let stream = TokenStream::new(tts);
                                 *tree = TokenTree::Delimited(*span, *spacing, *delim, stream);
                                 found = true;
                                 break;
@@ -242,7 +243,7 @@ impl AttrTokenStream {
                         );
                     }
                     for attr in outer_attrs {
-                        res.extend(attr.get_tokens().0.iter().cloned());
+                        res.extend(attr.token_trees());
                     }
                     res.extend(target_tokens);
                 }

compiler/rustc_expand/src/config.rs

@@ -292,8 +292,6 @@ impl<'a> StripUnconfigured<'a> {
         attr: &Attribute,
         (item, item_span): (ast::AttrItem, Span),
     ) -> Attribute {
-        let orig_tokens = attr.get_tokens();
-
         // We are taking an attribute of the form `#[cfg_attr(pred, attr)]`
         // and producing an attribute of the form `#[attr]`. We
         // have captured tokens for `attr` itself, but we need to
@@ -302,7 +300,7 @@ impl<'a> StripUnconfigured<'a> {
 
         // Use the `#` in `#[cfg_attr(pred, attr)]` as the `#` token
         // for `attr` when we expand it to `#[attr]`
-        let mut orig_trees = orig_tokens.trees();
+        let mut orig_trees = attr.token_trees().into_iter();
         let TokenTree::Token(pound_token @ Token { kind: TokenKind::Pound, .. }, _) =
             orig_trees.next().unwrap().clone()
         else {