Auto merge of #34652 - jseyfried:fix_expansion_perf, r=nrc

Fix expansion performance regression

**syntax-[breaking-change] cc #31645**

This fixes #34630 by reverting commit 5bf7970 of PR #33943, which landed in #34424.

By removing the `Rc<_>` wrapping around `Delimited` and `SequenceRepetition` in `TokenTree`, 5bf7970 made cloning `TokenTree`s more expensive. While this had no measurable performance impact on the compiler's crates, it caused an order of magnitude performance regression on some macro-heavy code in the wild. I believe this is due to clones of `TokenTree`s in `macro_parser.rs` and/or `macro_rules.rs`.

r? @nrc

1 files changed, 8 insertions, 7 deletions

diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index bbcc044d43c..9502bc48a3e 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -662,6 +662,7 @@ pub fn integer_lit(s: &str,
 #[cfg(test)]
 mod tests {
     use super::*;
+    use std::rc::Rc;
     use syntax_pos::{Span, BytePos, Pos, NO_EXPANSION};
     use codemap::Spanned;
     use ast::{self, PatKind};
@@ -763,7 +764,7 @@ mod tests {
                             )
                             if first_delimed.delim == token::Paren
                             && ident.name.as_str() == "a" => {},
-                            _ => panic!("value 3: {:?}", *first_delimed),
+                            _ => panic!("value 3: {:?}", **first_delimed),
                         }
                         let tts = &second_delimed.tts[..];
                         match (tts.len(), tts.get(0), tts.get(1)) {
@@ -774,10 +775,10 @@ mod tests {
                             )
                             if second_delimed.delim == token::Paren
                             && ident.name.as_str() == "a" => {},
-                            _ => panic!("value 4: {:?}", *second_delimed),
+                            _ => panic!("value 4: {:?}", **second_delimed),
                         }
                     },
-                    _ => panic!("value 2: {:?}", *macro_delimed),
+                    _ => panic!("value 2: {:?}", **macro_delimed),
                 }
             },
             _ => panic!("value: {:?}",tts),
@@ -793,7 +794,7 @@ mod tests {
             TokenTree::Token(sp(3, 4), token::Ident(str_to_ident("a"))),
             TokenTree::Delimited(
                 sp(5, 14),
-                tokenstream::Delimited {
+                Rc::new(tokenstream::Delimited {
                     delim: token::DelimToken::Paren,
                     open_span: sp(5, 6),
                     tts: vec![
@@ -802,10 +803,10 @@ mod tests {
                         TokenTree::Token(sp(10, 13), token::Ident(str_to_ident("i32"))),
                     ],
                     close_span: sp(13, 14),
-                }),
+                })),
             TokenTree::Delimited(
                 sp(15, 21),
-                tokenstream::Delimited {
+                Rc::new(tokenstream::Delimited {
                     delim: token::DelimToken::Brace,
                     open_span: sp(15, 16),
                     tts: vec![
@@ -813,7 +814,7 @@ mod tests {
                         TokenTree::Token(sp(18, 19), token::Semi),
                     ],
                     close_span: sp(20, 21),
-                })
+                }))
         ];
 
         assert_eq!(tts, expected);