Rollup merge of #111492 - calebcartwright:by-ref-tokentree-1, r=compiler-errors

use by ref TokenTree iterator to avoid a few clones

Just a handful of swaps from the by-value cursor to by-ref cursor so as to avoid some unnecessary clones.

I've been doing some analysis on internal cleanup opportunities within rustfmt and as part of that yak-shave I found myself perusing broader token stream and tree usage (which we use within rustfmt). As reflected in some inline comments on the cursor structs (not part of this diff), there's probably many other such cases throughout the code, but figured I'd start small with these while I had the time. May take a look at the other sites in the future

3 files changed, 6 insertions, 6 deletions

diff --git a/compiler/rustc_builtin_macros/src/concat_idents.rs b/compiler/rustc_builtin_macros/src/concat_idents.rs
index 8c737f04323..ee56d45c9c8 100644
--- a/compiler/rustc_builtin_macros/src/concat_idents.rs
+++ b/compiler/rustc_builtin_macros/src/concat_idents.rs
@@ -19,7 +19,7 @@ pub fn expand_concat_idents<'cx>(
     }
 
     let mut res_str = String::new();
-    for (i, e) in tts.into_trees().enumerate() {
+    for (i, e) in tts.trees().enumerate() {
         if i & 1 == 1 {
             match e {
                 TokenTree::Token(Token { kind: token::Comma, .. }, _) => {}
diff --git a/compiler/rustc_builtin_macros/src/trace_macros.rs b/compiler/rustc_builtin_macros/src/trace_macros.rs
index cc5ae6894e6..9c98723e1f4 100644
--- a/compiler/rustc_builtin_macros/src/trace_macros.rs
+++ b/compiler/rustc_builtin_macros/src/trace_macros.rs
@@ -8,7 +8,7 @@ pub fn expand_trace_macros(
     sp: Span,
     tt: TokenStream,
 ) -> Box<dyn base::MacResult + 'static> {
-    let mut cursor = tt.into_trees();
+    let mut cursor = tt.trees();
     let mut err = false;
     let value = match &cursor.next() {
         Some(TokenTree::Token(token, _)) if token.is_keyword(kw::True) => true,
diff --git a/compiler/rustc_lint/src/builtin.rs b/compiler/rustc_lint/src/builtin.rs
index 3025cce7ba7..b1c45eaf601 100644
--- a/compiler/rustc_lint/src/builtin.rs
+++ b/compiler/rustc_lint/src/builtin.rs
@@ -1882,8 +1882,8 @@ declare_lint_pass!(
 struct UnderMacro(bool);
 
 impl KeywordIdents {
-    fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: TokenStream) {
-        for tt in tokens.into_trees() {
+    fn check_tokens(&mut self, cx: &EarlyContext<'_>, tokens: &TokenStream) {
+        for tt in tokens.trees() {
             match tt {
                 // Only report non-raw idents.
                 TokenTree::Token(token, _) => {
@@ -1944,10 +1944,10 @@ impl KeywordIdents {
 
 impl EarlyLintPass for KeywordIdents {
     fn check_mac_def(&mut self, cx: &EarlyContext<'_>, mac_def: &ast::MacroDef) {
-        self.check_tokens(cx, mac_def.body.tokens.clone());
+        self.check_tokens(cx, &mac_def.body.tokens);
     }
     fn check_mac(&mut self, cx: &EarlyContext<'_>, mac: &ast::MacCall) {
-        self.check_tokens(cx, mac.args.tokens.clone());
+        self.check_tokens(cx, &mac.args.tokens);
     }
     fn check_ident(&mut self, cx: &EarlyContext<'_>, ident: Ident) {
         self.check_ident_token(cx, UnderMacro(false), ident);