Rollup merge of rust-lang#111548 - calebcartwright:by-ref-tokentree2,…

… r=compiler-errors

add util function to TokenStream to eliminate some clones

Another proposed change in the same vein as rust-lang#111492 trying to get rid of some clones.

This adds a TokenStream helper function so that rustdoc can directly get a chunks iterator over the underlying token trees so that it no longer needs the clones and vec.

compiler/rustc_ast/src/tokenstream.rs

@@ -551,6 +551,10 @@ impl TokenStream {
             vec_mut.extend(stream_iter);
         }
     }
+
+    pub fn chunks(&self, chunk_size: usize) -> core::slice::Chunks<'_, TokenTree> {
+        self.0.chunks(chunk_size)
+    }
 }
 
 /// By-reference iterator over a [`TokenStream`], that produces `&TokenTree`

src/librustdoc/clean/utils.rs

@@ -594,9 +594,8 @@ pub(super) fn display_macro_source(
     def_id: DefId,
     vis: ty::Visibility<DefId>,
 ) -> String {
-    let tts: Vec<_> = def.body.tokens.clone().into_trees().collect();
     // Extract the spans of all matchers. They represent the "interface" of the macro.
-    let matchers = tts.chunks(4).map(|arm| &arm[0]);
+    let matchers = def.body.tokens.chunks(4).map(|arm| &arm[0]);
 
     if def.macro_rules {
         format!("macro_rules! {} {{\n{}}}", name, render_macro_arms(cx.tcx, matchers, ";"))