Rollup merge of #37569 - jseyfried:improve_expansion_perf, r=eddyb

macros: improve expansion performance

This PR fixes that regression, further improves performance on recursive, `tt`-heavy workloads, and makes a variety of other improvements to parsing and expansion performance.

Expansion performance improvements:

| Test case      | Run-time | Memory usage |
| -------------- | -------- | ------------ |
| libsyntax      | 8%       | 10%          |
| librustc       | 15%      | 6%           |
| librustc_trans | 30%      | 6%           |
| #37074         | 20%      | 15%          |
| #34630         | 40%      | 8%           |

r? @eddyb

13 files changed, 294 insertions, 388 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index f077ead1f8e..f7581924eb1 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -1050,7 +1050,7 @@ pub enum ExprKind {
     Ret(Option<P<Expr>>),
 
     /// Output of the `asm!()` macro
-    InlineAsm(InlineAsm),
+    InlineAsm(P<InlineAsm>),
 
     /// A macro invocation; pre-expansion
     Mac(Mac),
diff --git a/src/libsyntax/ext/base.rs b/src/libsyntax/ext/base.rs
index cc097ab0efa..1f47a91fcc1 100644
--- a/src/libsyntax/ext/base.rs
+++ b/src/libsyntax/ext/base.rs
@@ -615,7 +615,9 @@ impl<'a> ExtCtxt<'a> {
 
     pub fn new_parser_from_tts(&self, tts: &[tokenstream::TokenTree])
         -> parser::Parser<'a> {
-        parse::tts_to_parser(self.parse_sess, tts.to_vec())
+        let mut parser = parse::tts_to_parser(self.parse_sess, tts.to_vec());
+        parser.allow_interpolated_tts = false; // FIXME(jseyfried) `quote!` can't handle these yet
+        parser
     }
     pub fn codemap(&self) -> &'a CodeMap { self.parse_sess.codemap() }
     pub fn parse_sess(&self) -> &'a parse::ParseSess { self.parse_sess }
diff --git a/src/libsyntax/ext/quote.rs b/src/libsyntax/ext/quote.rs
index f21360755bc..969cfa292ce 100644
--- a/src/libsyntax/ext/quote.rs
+++ b/src/libsyntax/ext/quote.rs
@@ -80,67 +80,71 @@ pub mod rt {
 
     impl ToTokens for ast::Path {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP,
-                                  token::Interpolated(token::NtPath(Box::new(self.clone()))))]
+            let nt = token::NtPath(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::Ty {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span, token::Interpolated(token::NtTy(P(self.clone()))))]
+            let nt = token::NtTy(P(self.clone()));
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::Block {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span, token::Interpolated(token::NtBlock(P(self.clone()))))]
+            let nt = token::NtBlock(P(self.clone()));
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::Generics {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(token::NtGenerics(self.clone())))]
+            let nt = token::NtGenerics(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::WhereClause {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP,
-                                  token::Interpolated(token::NtWhereClause(self.clone())))]
+            let nt = token::NtWhereClause(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for P<ast::Item> {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span, token::Interpolated(token::NtItem(self.clone())))]
+            let nt = token::NtItem(self.clone());
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::ImplItem {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span,
-                                  token::Interpolated(token::NtImplItem(P(self.clone()))))]
+            let nt = token::NtImplItem(self.clone());
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for P<ast::ImplItem> {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span, token::Interpolated(token::NtImplItem(self.clone())))]
+            let nt = token::NtImplItem((**self).clone());
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::TraitItem {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span,
-                                  token::Interpolated(token::NtTraitItem(P(self.clone()))))]
+            let nt = token::NtTraitItem(self.clone());
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::Stmt {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            let mut tts = vec![
-                TokenTree::Token(self.span, token::Interpolated(token::NtStmt(P(self.clone()))))
-            ];
+            let nt = token::NtStmt(self.clone());
+            let mut tts = vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))];
 
             // Some statements require a trailing semicolon.
             if classify::stmt_ends_with_semi(&self.node) {
@@ -153,31 +157,36 @@ pub mod rt {
 
     impl ToTokens for P<ast::Expr> {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span, token::Interpolated(token::NtExpr(self.clone())))]
+            let nt = token::NtExpr(self.clone());
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for P<ast::Pat> {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(self.span, token::Interpolated(token::NtPat(self.clone())))]
+            let nt = token::NtPat(self.clone());
+            vec![TokenTree::Token(self.span, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::Arm {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(token::NtArm(self.clone())))]
+            let nt = token::NtArm(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for ast::Arg {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(token::NtArg(self.clone())))]
+            let nt = token::NtArg(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
     impl ToTokens for P<ast::Block> {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(token::NtBlock(self.clone())))]
+            let nt = token::NtBlock(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
@@ -204,7 +213,8 @@ pub mod rt {
 
     impl ToTokens for P<ast::MetaItem> {
         fn to_tokens(&self, _cx: &ExtCtxt) -> Vec<TokenTree> {
-            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(token::NtMeta(self.clone())))]
+            let nt = token::NtMeta(self.clone());
+            vec![TokenTree::Token(DUMMY_SP, token::Interpolated(Rc::new(nt)))]
         }
     }
 
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 7e3fe328569..1066646aa8e 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -89,7 +89,6 @@ use parse::token::{DocComment, MatchNt, SubstNt};
 use parse::token::{Token, Nonterminal};
 use parse::token;
 use print::pprust;
-use ptr::P;
 use tokenstream::{self, TokenTree};
 use util::small_vector::SmallVector;
 
@@ -198,7 +197,7 @@ pub fn initial_matcher_pos(ms: Vec<TokenTree>, sep: Option<Token>, lo: BytePos)
 
 pub enum NamedMatch {
     MatchedSeq(Vec<Rc<NamedMatch>>, syntax_pos::Span),
-    MatchedNonterminal(Nonterminal)
+    MatchedNonterminal(Rc<Nonterminal>)
 }
 
 pub fn nameize(p_s: &ParseSess, ms: &[TokenTree], res: &[Rc<NamedMatch>])
@@ -279,17 +278,16 @@ pub fn token_name_eq(t1 : &Token, t2 : &Token) -> bool {
     }
 }
 
-pub fn parse(sess: &ParseSess, mut rdr: TtReader, ms: &[TokenTree]) -> NamedParseResult {
-    let mut cur_eis = SmallVector::one(initial_matcher_pos(ms.to_owned(),
-                                                           None,
-                                                           rdr.peek().sp.lo));
+pub fn parse(sess: &ParseSess, rdr: TtReader, ms: &[TokenTree]) -> NamedParseResult {
+    let mut parser = Parser::new_with_doc_flag(sess, Box::new(rdr), true);
+    let mut cur_eis = SmallVector::one(initial_matcher_pos(ms.to_owned(), None, parser.span.lo));
 
     loop {
         let mut bb_eis = Vec::new(); // black-box parsed by parser.rs
         let mut next_eis = Vec::new(); // or proceed normally
         let mut eof_eis = Vec::new();
 
-        let TokenAndSpan { tok, sp } = rdr.peek();
+        let (sp, tok) = (parser.span, parser.token.clone());
 
         /* we append new items to this while we go */
         loop {
@@ -474,23 +472,19 @@ pub fn parse(sess: &ParseSess, mut rdr: TtReader, ms: &[TokenTree]) -> NamedPars
                 while !next_eis.is_empty() {
                     cur_eis.push(next_eis.pop().unwrap());
                 }
-                rdr.next_token();
+                parser.bump();
             } else /* bb_eis.len() == 1 */ {
-                rdr.next_tok = {
-                    let mut rust_parser = Parser::new(sess, Box::new(&mut rdr));
-                    let mut ei = bb_eis.pop().unwrap();
-                    if let TokenTree::Token(span, MatchNt(_, ident)) = ei.top_elts.get_tt(ei.idx) {
-                        let match_cur = ei.match_cur;
-                        (&mut ei.matches[match_cur]).push(Rc::new(MatchedNonterminal(
-                            parse_nt(&mut rust_parser, span, &ident.name.as_str()))));
-                        ei.idx += 1;
-                        ei.match_cur += 1;
-                    } else {
-                        unreachable!()
-                    }
-                    cur_eis.push(ei);
-                    Some(TokenAndSpan { tok: rust_parser.token, sp: rust_parser.span })
-                };
+                let mut ei = bb_eis.pop().unwrap();
+                if let TokenTree::Token(span, MatchNt(_, ident)) = ei.top_elts.get_tt(ei.idx) {
+                    let match_cur = ei.match_cur;
+                    (&mut ei.matches[match_cur]).push(Rc::new(MatchedNonterminal(
+                        Rc::new(parse_nt(&mut parser, span, &ident.name.as_str())))));
+                    ei.idx += 1;
+                    ei.match_cur += 1;
+                } else {
+                    unreachable!()
+                }
+                cur_eis.push(ei);
             }
         }
 
@@ -502,10 +496,19 @@ pub fn parse_nt<'a>(p: &mut Parser<'a>, sp: Span, name: &str) -> Nonterminal {
     match name {
         "tt" => {
             p.quote_depth += 1; //but in theory, non-quoted tts might be useful
-            let res: ::parse::PResult<'a, _> = p.parse_token_tree();
-            let res = token::NtTT(P(panictry!(res)));
+            let mut tt = panictry!(p.parse_token_tree());
             p.quote_depth -= 1;
-            return res;
+            loop {
+                let nt = match tt {
+                    TokenTree::Token(_, token::Interpolated(ref nt)) => nt.clone(),
+                    _ => break,
+                };
+                match *nt {
+                    token::NtTT(ref sub_tt) => tt = sub_tt.clone(),
+                    _ => break,
+                }
+            }
+            return token::NtTT(tt);
         }
         _ => {}
     }
@@ -521,7 +524,7 @@ pub fn parse_nt<'a>(p: &mut Parser<'a>, sp: Span, name: &str) -> Nonterminal {
         },
         "block" => token::NtBlock(panictry!(p.parse_block())),
         "stmt" => match panictry!(p.parse_stmt()) {
-            Some(s) => token::NtStmt(P(s)),
+            Some(s) => token::NtStmt(s),
             None => {
                 p.fatal("expected a statement").emit();
                 panic!(FatalError);
@@ -534,7 +537,7 @@ pub fn parse_nt<'a>(p: &mut Parser<'a>, sp: Span, name: &str) -> Nonterminal {
         "ident" => match p.token {
             token::Ident(sn) => {
                 p.bump();
-                token::NtIdent(Box::new(Spanned::<Ident>{node: sn, span: p.span}))
+                token::NtIdent(Spanned::<Ident>{node: sn, span: p.span})
             }
             _ => {
                 let token_str = pprust::token_to_string(&p.token);
@@ -544,7 +547,7 @@ pub fn parse_nt<'a>(p: &mut Parser<'a>, sp: Span, name: &str) -> Nonterminal {
             }
         },
         "path" => {
-            token::NtPath(Box::new(panictry!(p.parse_path(PathStyle::Type))))
+            token::NtPath(panictry!(p.parse_path(PathStyle::Type)))
         },
         "meta" => token::NtMeta(panictry!(p.parse_meta_item())),
         // this is not supposed to happen, since it has been checked
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 431e757368c..552d4de9617 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -236,12 +236,14 @@ pub fn compile(sess: &ParseSess, def: &ast::MacroDef) -> SyntaxExtension {
     // Extract the arguments:
     let lhses = match **argument_map.get(&lhs_nm).unwrap() {
         MatchedSeq(ref s, _) => {
-            s.iter().map(|m| match **m {
-                MatchedNonterminal(NtTT(ref tt)) => {
-                    valid &= check_lhs_nt_follows(sess, tt);
-                    (**tt).clone()
+            s.iter().map(|m| {
+                if let MatchedNonterminal(ref nt) = **m {
+                    if let NtTT(ref tt) = **nt {
+                        valid &= check_lhs_nt_follows(sess, tt);
+                        return (*tt).clone();
+                    }
                 }
-                _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
+                sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
             }).collect::<Vec<TokenTree>>()
         }
         _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
@@ -249,9 +251,13 @@ pub fn compile(sess: &ParseSess, def: &ast::MacroDef) -> SyntaxExtension {
 
     let rhses = match **argument_map.get(&rhs_nm).unwrap() {
         MatchedSeq(ref s, _) => {
-            s.iter().map(|m| match **m {
-                MatchedNonterminal(NtTT(ref tt)) => (**tt).clone(),
-                _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured rhs")
+            s.iter().map(|m| {
+                if let MatchedNonterminal(ref nt) = **m {
+                    if let NtTT(ref tt) = **nt {
+                        return (*tt).clone();
+                    }
+                }
+                sess.span_diagnostic.span_bug(def.span, "wrong-structured lhs")
             }).collect()
         }
         _ => sess.span_diagnostic.span_bug(def.span, "wrong-structured rhs")
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 8a6a8e53a3e..37e329e5d3b 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -12,9 +12,7 @@ use self::LockstepIterSize::*;
 use ast::Ident;
 use errors::{Handler, DiagnosticBuilder};
 use ext::tt::macro_parser::{NamedMatch, MatchedSeq, MatchedNonterminal};
-use parse::token::{DocComment, MatchNt, SubstNt};
-use parse::token::{Token, Interpolated, NtIdent, NtTT};
-use parse::token;
+use parse::token::{self, MatchNt, SubstNt, Token, NtIdent};
 use parse::lexer::TokenAndSpan;
 use syntax_pos::{Span, DUMMY_SP};
 use tokenstream::{self, TokenTree};
@@ -46,9 +44,7 @@ pub struct TtReader<'a> {
     /* cached: */
     pub cur_tok: Token,
     pub cur_span: Span,
-    pub next_tok: Option<TokenAndSpan>,
     /// Transform doc comments. Only useful in macro invocations
-    pub desugar_doc_comments: bool,
     pub fatal_errs: Vec<DiagnosticBuilder<'a>>,
 }
 
@@ -59,20 +55,6 @@ pub fn new_tt_reader(sp_diag: &Handler,
                      interp: Option<HashMap<Ident, Rc<NamedMatch>>>,
                      src: Vec<tokenstream::TokenTree>)
                      -> TtReader {
-    new_tt_reader_with_doc_flag(sp_diag, interp, src, false)
-}
-
-/// The extra `desugar_doc_comments` flag enables reading doc comments
-/// like any other attribute which consists of `meta` and surrounding #[ ] tokens.
-///
-/// This can do Macro-By-Example transcription. On the other hand, if
-/// `src` contains no `TokenTree::Sequence`s, `MatchNt`s or `SubstNt`s, `interp` can
-/// (and should) be None.
-pub fn new_tt_reader_with_doc_flag(sp_diag: &Handler,
-                                   interp: Option<HashMap<Ident, Rc<NamedMatch>>>,
-                                   src: Vec<tokenstream::TokenTree>,
-                                   desugar_doc_comments: bool)
-                                   -> TtReader {
     let mut r = TtReader {
         sp_diag: sp_diag,
         stack: SmallVector::one(TtFrame {
@@ -91,11 +73,9 @@ pub fn new_tt_reader_with_doc_flag(sp_diag: &Handler,
         },
         repeat_idx: Vec::new(),
         repeat_len: Vec::new(),
-        desugar_doc_comments: desugar_doc_comments,
         /* dummy values, never read: */
         cur_tok: token::Eof,
         cur_span: DUMMY_SP,
-        next_tok: None,
         fatal_errs: Vec::new(),
     };
     tt_next_token(&mut r); /* get cur_tok and cur_span set up */
@@ -174,9 +154,6 @@ fn lockstep_iter_size(t: &TokenTree, r: &TtReader) -> LockstepIterSize {
 /// Return the next token from the TtReader.
 /// EFFECT: advances the reader's token field
 pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
-    if let Some(tok) = r.next_tok.take() {
-        return tok;
-    }
     // FIXME(pcwalton): Bad copy?
     let ret_val = TokenAndSpan {
         tok: r.cur_tok.clone(),
@@ -269,47 +246,35 @@ pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
             }
             // FIXME #2887: think about span stuff here
             TokenTree::Token(sp, SubstNt(ident)) => {
+                r.stack.last_mut().unwrap().idx += 1;
                 match lookup_cur_matched(r, ident) {
                     None => {
-                        r.stack.last_mut().unwrap().idx += 1;
                         r.cur_span = sp;
                         r.cur_tok = SubstNt(ident);
                         return ret_val;
                         // this can't be 0 length, just like TokenTree::Delimited
                     }
-                    Some(cur_matched) => {
-                        match *cur_matched {
+                    Some(cur_matched) => if let MatchedNonterminal(ref nt) = *cur_matched {
+                        match **nt {
                             // sidestep the interpolation tricks for ident because
                             // (a) idents can be in lots of places, so it'd be a pain
                             // (b) we actually can, since it's a token.
-                            MatchedNonterminal(NtIdent(ref sn)) => {
-                                r.stack.last_mut().unwrap().idx += 1;
+                            NtIdent(ref sn) => {
                                 r.cur_span = sn.span;
                                 r.cur_tok = token::Ident(sn.node);
                                 return ret_val;
                             }
-                            MatchedNonterminal(NtTT(ref tt)) => {
-                                r.stack.push(TtFrame {
-                                    forest: TokenTree::Token(sp, Interpolated(NtTT(tt.clone()))),
-                                    idx: 0,
-                                    dotdotdoted: false,
-                                    sep: None,
-                                });
-                            }
-                            MatchedNonterminal(ref other_whole_nt) => {
-                                r.stack.last_mut().unwrap().idx += 1;
+                            _ => {
                                 // FIXME(pcwalton): Bad copy.
                                 r.cur_span = sp;
-                                r.cur_tok = Interpolated((*other_whole_nt).clone());
+                                r.cur_tok = token::Interpolated(nt.clone());
                                 return ret_val;
                             }
-                            MatchedSeq(..) => {
-                                panic!(r.sp_diag.span_fatal(
-                                    sp, /* blame the macro writer */
-                                    &format!("variable '{}' is still repeating at this depth",
-                                            ident)));
-                            }
                         }
+                    } else {
+                        panic!(r.sp_diag.span_fatal(
+                            sp, /* blame the macro writer */
+                            &format!("variable '{}' is still repeating at this depth", ident)));
                     }
                 }
             }
@@ -324,14 +289,6 @@ pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
                 });
                 // if this could be 0-length, we'd need to potentially recur here
             }
-            TokenTree::Token(sp, DocComment(name)) if r.desugar_doc_comments => {
-                r.stack.push(TtFrame {
-                   forest: TokenTree::Token(sp, DocComment(name)),
-                   idx: 0,
-                   dotdotdoted: false,
-                   sep: None
-                });
-            }
             TokenTree::Token(sp, tok) => {
                 r.cur_span = sp;
                 r.cur_tok = tok;
diff --git a/src/libsyntax/fold.rs b/src/libsyntax/fold.rs
index 4bf6e55d674..1deeaf42231 100644
--- a/src/libsyntax/fold.rs
+++ b/src/libsyntax/fold.rs
@@ -576,7 +576,13 @@ pub fn noop_fold_token<T: Folder>(t: token::Token, fld: &mut T) -> token::Token
     match t {
         token::Ident(id) => token::Ident(fld.fold_ident(id)),
         token::Lifetime(id) => token::Lifetime(fld.fold_ident(id)),
-        token::Interpolated(nt) => token::Interpolated(fld.fold_interpolated(nt)),
+        token::Interpolated(nt) => {
+            let nt = match Rc::try_unwrap(nt) {
+                Ok(nt) => nt,
+                Err(nt) => (*nt).clone(),
+            };
+            token::Interpolated(Rc::new(fld.fold_interpolated(nt)))
+        }
         token::SubstNt(ident) => token::SubstNt(fld.fold_ident(ident)),
         token::MatchNt(name, kind) => token::MatchNt(fld.fold_ident(name), fld.fold_ident(kind)),
         _ => t
@@ -614,26 +620,25 @@ pub fn noop_fold_interpolated<T: Folder>(nt: token::Nonterminal, fld: &mut T)
                           .expect_one("expected fold to produce exactly one item")),
         token::NtBlock(block) => token::NtBlock(fld.fold_block(block)),
         token::NtStmt(stmt) =>
-            token::NtStmt(stmt.map(|stmt| fld.fold_stmt(stmt)
+            token::NtStmt(fld.fold_stmt(stmt)
                           // this is probably okay, because the only folds likely
                           // to peek inside interpolated nodes will be renamings/markings,
                           // which map single items to single items
-                          .expect_one("expected fold to produce exactly one statement"))),
+                          .expect_one("expected fold to produce exactly one statement")),
         token::NtPat(pat) => token::NtPat(fld.fold_pat(pat)),
         token::NtExpr(expr) => token::NtExpr(fld.fold_expr(expr)),
         token::NtTy(ty) => token::NtTy(fld.fold_ty(ty)),
-        token::NtIdent(id) =>
-            token::NtIdent(Box::new(Spanned::<Ident>{node: fld.fold_ident(id.node), ..*id})),
+        token::NtIdent(id) => token::NtIdent(Spanned::<Ident>{node: fld.fold_ident(id.node), ..id}),
         token::NtMeta(meta_item) => token::NtMeta(fld.fold_meta_item(meta_item)),
-        token::NtPath(path) => token::NtPath(Box::new(fld.fold_path(*path))),
-        token::NtTT(tt) => token::NtTT(P(fld.fold_tt(&tt))),
+        token::NtPath(path) => token::NtPath(fld.fold_path(path)),
+        token::NtTT(tt) => token::NtTT(fld.fold_tt(&tt)),
         token::NtArm(arm) => token::NtArm(fld.fold_arm(arm)),
-        token::NtImplItem(arm) =>
-            token::NtImplItem(arm.map(|arm| fld.fold_impl_item(arm)
-                              .expect_one("expected fold to produce exactly one item"))),
-        token::NtTraitItem(arm) =>
-            token::NtTraitItem(arm.map(|arm| fld.fold_trait_item(arm)
-                               .expect_one("expected fold to produce exactly one item"))),
+        token::NtImplItem(item) =>
+            token::NtImplItem(fld.fold_impl_item(item)
+                              .expect_one("expected fold to produce exactly one item")),
+        token::NtTraitItem(item) =>
+            token::NtTraitItem(fld.fold_trait_item(item)
+                               .expect_one("expected fold to produce exactly one item")),
         token::NtGenerics(generics) => token::NtGenerics(fld.fold_generics(generics)),
         token::NtWhereClause(where_clause) =>
             token::NtWhereClause(fld.fold_where_clause(where_clause)),
@@ -1244,36 +1249,22 @@ pub fn noop_fold_expr<T: Folder>(Expr {id, node, span, attrs}: Expr, folder: &mu
                        folder.fold_ident(label.node)))
             ),
             ExprKind::Ret(e) => ExprKind::Ret(e.map(|x| folder.fold_expr(x))),
-            ExprKind::InlineAsm(InlineAsm {
-                inputs,
-                outputs,
-                asm,
-                asm_str_style,
-                clobbers,
-                volatile,
-                alignstack,
-                dialect,
-                expn_id,
-            }) => ExprKind::InlineAsm(InlineAsm {
-                inputs: inputs.move_map(|(c, input)| {
-                    (c, folder.fold_expr(input))
-                }),
-                outputs: outputs.move_map(|out| {
-                    InlineAsmOutput {
-                        constraint: out.constraint,
-                        expr: folder.fold_expr(out.expr),
-                        is_rw: out.is_rw,
-                        is_indirect: out.is_indirect,
-                    }
-                }),
-                asm: asm,
-                asm_str_style: asm_str_style,
-                clobbers: clobbers,
-                volatile: volatile,
-                alignstack: alignstack,
-                dialect: dialect,
-                expn_id: expn_id,
-            }),
+            ExprKind::InlineAsm(asm) => ExprKind::InlineAsm(asm.map(|asm| {
+                InlineAsm {
+                    inputs: asm.inputs.move_map(|(c, input)| {
+                        (c, folder.fold_expr(input))
+                    }),
+                    outputs: asm.outputs.move_map(|out| {
+                        InlineAsmOutput {
+                            constraint: out.constraint,
+                            expr: folder.fold_expr(out.expr),
+                            is_rw: out.is_rw,
+                            is_indirect: out.is_indirect,
+                        }
+                    }),
+                    ..asm
+                }
+            })),
             ExprKind::Mac(mac) => ExprKind::Mac(folder.fold_mac(mac)),
             ExprKind::Struct(path, fields, maybe_expr) => {
                 ExprKind::Struct(folder.fold_path(path),
diff --git a/src/libsyntax/parse/attr.rs b/src/libsyntax/parse/attr.rs
index 3cb34fa3c91..983c882eafc 100644
--- a/src/libsyntax/parse/attr.rs
+++ b/src/libsyntax/parse/attr.rs
@@ -215,7 +215,10 @@ impl<'a> Parser<'a> {
     /// meta_item_inner : (meta_item | UNSUFFIXED_LIT) (',' meta_item_inner)? ;
     pub fn parse_meta_item(&mut self) -> PResult<'a, P<ast::MetaItem>> {
         let nt_meta = match self.token {
-            token::Interpolated(token::NtMeta(ref e)) => Some(e.clone()),
+            token::Interpolated(ref nt) => match **nt {
+                token::NtMeta(ref e) => Some(e.clone()),
+                _ => None,
+            },
             _ => None,
         };
 
diff --git a/src/libsyntax/parse/lexer/mod.rs b/src/libsyntax/parse/lexer/mod.rs
index 5e20f6e4192..cf48c445c80 100644
--- a/src/libsyntax/parse/lexer/mod.rs
+++ b/src/libsyntax/parse/lexer/mod.rs
@@ -22,7 +22,7 @@ use std::char;
 use std::mem::replace;
 use std::rc::Rc;
 
-pub use ext::tt::transcribe::{TtReader, new_tt_reader, new_tt_reader_with_doc_flag};
+pub use ext::tt::transcribe::{TtReader, new_tt_reader};
 
 pub mod comments;
 mod unicode_chars;
@@ -171,31 +171,10 @@ impl<'a> Reader for TtReader<'a> {
         self.fatal_errs.clear();
     }
     fn peek(&self) -> TokenAndSpan {
-        self.next_tok.clone().unwrap_or(TokenAndSpan {
+        TokenAndSpan {
             tok: self.cur_tok.clone(),
             sp: self.cur_span,
-        })
-    }
-}
-
-impl<'a, 'b> Reader for &'b mut TtReader<'a> {
-    fn is_eof(&self) -> bool {
-        (**self).is_eof()
-    }
-    fn try_next_token(&mut self) -> Result<TokenAndSpan, ()> {
-        (**self).try_next_token()
-    }
-    fn fatal(&self, m: &str) -> FatalError {
-        (**self).fatal(m)
-    }
-    fn err(&self, m: &str) {
-        (**self).err(m)
-    }
-    fn emit_fatal_errors(&mut self) {
-        (**self).emit_fatal_errors()
-    }
-    fn peek(&self) -> TokenAndSpan {
-        (**self).peek()
+        }
     }
 }
 
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index b80aa667be6..b670a738473 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -107,125 +107,41 @@ pub enum SemiColonMode {
 /// be. The important thing is to make sure that lookahead doesn't balk at
 /// `token::Interpolated` tokens.
 macro_rules! maybe_whole_expr {
-    ($p:expr) => (
-        {
-            let found = match $p.token {
-                token::Interpolated(token::NtExpr(ref e)) => {
-                    Some((*e).clone())
+    ($p:expr) => {
+        if let token::Interpolated(nt) = $p.token.clone() {
+            match *nt {
+                token::NtExpr(ref e) => {
+                    $p.bump();
+                    return Ok((*e).clone());
                 }
-                token::Interpolated(token::NtPath(_)) => {
-                    // FIXME: The following avoids an issue with lexical borrowck scopes,
-                    // but the clone is unfortunate.
-                    let pt = match $p.token {
-                        token::Interpolated(token::NtPath(ref pt)) => (**pt).clone(),
-                        _ => unreachable!()
-                    };
+                token::NtPath(ref path) => {
+                    $p.bump();
                     let span = $p.span;
-                    Some($p.mk_expr(span.lo, span.hi, ExprKind::Path(None, pt), ThinVec::new()))
+                    let kind = ExprKind::Path(None, (*path).clone());
+                    return Ok($p.mk_expr(span.lo, span.hi, kind, ThinVec::new()));
                 }
-                token::Interpolated(token::NtBlock(_)) => {
-                    // FIXME: The following avoids an issue with lexical borrowck scopes,
-                    // but the clone is unfortunate.
-                    let b = match $p.token {
-                        token::Interpolated(token::NtBlock(ref b)) => (*b).clone(),
-                        _ => unreachable!()
-                    };
+                token::NtBlock(ref block) => {
+                    $p.bump();
                     let span = $p.span;
-                    Some($p.mk_expr(span.lo, span.hi, ExprKind::Block(b), ThinVec::new()))
+                    let kind = ExprKind::Block((*block).clone());
+                    return Ok($p.mk_expr(span.lo, span.hi, kind, ThinVec::new()));
                 }
-                _ => None
+                _ => {},
             };
-            match found {
-                Some(e) => {
-                    $p.bump();
-                    return Ok(e);
-                }
-                None => ()
-            }
         }
-    )
+    }
 }
 
 /// As maybe_whole_expr, but for things other than expressions
 macro_rules! maybe_whole {
-    ($p:expr, $constructor:ident) => (
-        {
-            let found = match ($p).token {
-                token::Interpolated(token::$constructor(_)) => {
-                    Some(($p).bump_and_get())
-                }
-                _ => None
-            };
-            if let Some(token::Interpolated(token::$constructor(x))) = found {
-                return Ok(x.clone());
+    ($p:expr, $constructor:ident, |$x:ident| $e:expr) => {
+        if let token::Interpolated(nt) = $p.token.clone() {
+            if let token::$constructor($x) = (*nt).clone() {
+                $p.bump();
+                return Ok($e);
             }
         }
-    );
-    (no_clone $p:expr, $constructor:ident) => (
-        {
-            let found = match ($p).token {
-                token::Interpolated(token::$constructor(_)) => {
-                    Some(($p).bump_and_get())
-                }
-                _ => None
-            };
-            if let Some(token::Interpolated(token::$constructor(x))) = found {
-                return Ok(x);
-            }
-        }
-    );
-    (no_clone_from_p $p:expr, $constructor:ident) => (
-        {
-            let found = match ($p).token {
-                token::Interpolated(token::$constructor(_)) => {
-                    Some(($p).bump_and_get())
-                }
-                _ => None
-            };
-            if let Some(token::Interpolated(token::$constructor(x))) = found {
-                return Ok(x.unwrap());
-            }
-        }
-    );
-    (deref $p:expr, $constructor:ident) => (
-        {
-            let found = match ($p).token {
-                token::Interpolated(token::$constructor(_)) => {
-                    Some(($p).bump_and_get())
-                }
-                _ => None
-            };
-            if let Some(token::Interpolated(token::$constructor(x))) = found {
-                return Ok((*x).clone());
-            }
-        }
-    );
-    (Some deref $p:expr, $constructor:ident) => (
-        {
-            let found = match ($p).token {
-                token::Interpolated(token::$constructor(_)) => {
-                    Some(($p).bump_and_get())
-                }
-                _ => None
-            };
-            if let Some(token::Interpolated(token::$constructor(x))) = found {
-                return Ok(Some((*x).clone()));
-            }
-        }
-    );
-    (pair_empty $p:expr, $constructor:ident) => (
-        {
-            let found = match ($p).token {
-                token::Interpolated(token::$constructor(_)) => {
-                    Some(($p).bump_and_get())
-                }
-                _ => None
-            };
-            if let Some(token::Interpolated(token::$constructor(x))) = found {
-                return Ok((Vec::new(), x));
-            }
-        }
-    )
+    };
 }
 
 fn maybe_append(mut lhs: Vec<Attribute>, rhs: Option<Vec<Attribute>>)
@@ -294,6 +210,9 @@ pub struct Parser<'a> {
     /// into modules, and sub-parsers have new values for this name.
     pub root_module_name: Option<String>,
     pub expected_tokens: Vec<TokenType>,
+    pub tts: Vec<(TokenTree, usize)>,
+    pub desugar_doc_comments: bool,
+    pub allow_interpolated_tts: bool,
 }
 
 #[derive(PartialEq, Eq, Clone)]
@@ -357,21 +276,18 @@ impl From<P<Expr>> for LhsExpr {
 }
 
 impl<'a> Parser<'a> {
-    pub fn new(sess: &'a ParseSess, mut rdr: Box<Reader+'a>) -> Self {
-        let tok0 = rdr.real_token();
-        let span = tok0.sp;
-        let mut directory = match span {
-            syntax_pos::DUMMY_SP => PathBuf::new(),
-            _ => PathBuf::from(sess.codemap().span_to_filename(span)),
-        };
-        directory.pop();
+    pub fn new(sess: &'a ParseSess, rdr: Box<Reader+'a>) -> Self {
+        Parser::new_with_doc_flag(sess, rdr, false)
+    }
 
-        Parser {
+    pub fn new_with_doc_flag(sess: &'a ParseSess, rdr: Box<Reader+'a>, desugar_doc_comments: bool)
+                             -> Self {
+        let mut parser = Parser {
             reader: rdr,
             sess: sess,
-            token: tok0.tok,
-            span: span,
-            prev_span: span,
+            token: token::Underscore,
+            span: syntax_pos::DUMMY_SP,
+            prev_span: syntax_pos::DUMMY_SP,
             prev_token_kind: PrevTokenKind::Other,
             lookahead_buffer: Default::default(),
             tokens_consumed: 0,
@@ -379,11 +295,63 @@ impl<'a> Parser<'a> {
             quote_depth: 0,
             parsing_token_tree: false,
             obsolete_set: HashSet::new(),
-            directory: directory,
+            directory: PathBuf::new(),
             open_braces: Vec::new(),
             owns_directory: true,
             root_module_name: None,
             expected_tokens: Vec::new(),
+            tts: Vec::new(),
+            desugar_doc_comments: desugar_doc_comments,
+            allow_interpolated_tts: true,
+        };
+
+        let tok = parser.next_tok();
+        parser.token = tok.tok;
+        parser.span = tok.sp;
+        if parser.span != syntax_pos::DUMMY_SP {
+            parser.directory = PathBuf::from(sess.codemap().span_to_filename(parser.span));
+            parser.directory.pop();
+        }
+        parser
+    }
+
+    fn next_tok(&mut self) -> TokenAndSpan {
+        'outer: loop {
+            let mut tok = if let Some((tts, i)) = self.tts.pop() {
+                let tt = tts.get_tt(i);
+                if i + 1 < tts.len() {
+                    self.tts.push((tts, i + 1));
+                }
+                if let TokenTree::Token(sp, tok) = tt {
+                    TokenAndSpan { tok: tok, sp: sp }
+                } else {
+                    self.tts.push((tt, 0));
+                    continue
+                }
+            } else {
+                self.reader.real_token()
+            };
+
+            loop {
+                let nt = match tok.tok {
+                    token::Interpolated(ref nt) => nt.clone(),
+                    token::DocComment(name) if self.desugar_doc_comments => {
+                        self.tts.push((TokenTree::Token(tok.sp, token::DocComment(name)), 0));
+                        continue 'outer
+                    }
+                    _ => return tok,
+                };
+                match *nt {
+                    token::NtTT(TokenTree::Token(sp, ref t)) => {
+                        tok = TokenAndSpan { tok: t.clone(), sp: sp };
+                    }
+                    token::NtTT(ref tt) => {
+                        self.tts.push((tt.clone(), 0));
+                        continue 'outer
+                    }
+                    _ => return tok,
+                }
+            }
         }
     }
 
@@ -516,9 +484,6 @@ impl<'a> Parser<'a> {
                 self.bump();
                 Ok(i)
             }
-            token::Interpolated(token::NtIdent(..)) => {
-                self.bug("ident interpolation not converted to real token");
-            }
             _ => {
                 Err(if self.prev_token_kind == PrevTokenKind::DocComment {
                     self.span_fatal_help(self.prev_span,
@@ -935,7 +900,7 @@ impl<'a> Parser<'a> {
         };
 
         let next = if self.lookahead_buffer.start == self.lookahead_buffer.end {
-            self.reader.real_token()
+            self.next_tok()
         } else {
             // Avoid token copies with `replace`.
             let old_start = self.lookahead_buffer.start;
@@ -980,7 +945,7 @@ impl<'a> Parser<'a> {
             f(&self.token)
         } else if dist < LOOKAHEAD_BUFFER_CAPACITY {
             while self.lookahead_buffer.len() < dist {
-                self.lookahead_buffer.buffer[self.lookahead_buffer.end] = self.reader.real_token();
+                self.lookahead_buffer.buffer[self.lookahead_buffer.end] = self.next_tok();
                 self.lookahead_buffer.end =
                     (self.lookahead_buffer.end + 1) % LOOKAHEAD_BUFFER_CAPACITY;
             }
@@ -1162,7 +1127,7 @@ impl<'a> Parser<'a> {
 
     /// Parse the items in a trait declaration
     pub fn parse_trait_item(&mut self) -> PResult<'a, TraitItem> {
-        maybe_whole!(no_clone_from_p self, NtTraitItem);
+        maybe_whole!(self, NtTraitItem, |x| x);
         let mut attrs = self.parse_outer_attributes()?;
         let lo = self.span.lo;
 
@@ -1331,7 +1296,7 @@ impl<'a> Parser<'a> {
 
     /// Parse a type.
     pub fn parse_ty(&mut self) -> PResult<'a, P<Ty>> {
-        maybe_whole!(no_clone self, NtTy);
+        maybe_whole!(self, NtTy, |x| x);
 
         let lo = self.span.lo;
 
@@ -1476,7 +1441,7 @@ impl<'a> Parser<'a> {
     /// This version of parse arg doesn't necessarily require
     /// identifier names.
     pub fn parse_arg_general(&mut self, require_name: bool) -> PResult<'a, Arg> {
-        maybe_whole!(no_clone self, NtArg);
+        maybe_whole!(self, NtArg, |x| x);
 
         let pat = if require_name || self.is_named_argument() {
             debug!("parse_arg_general parse_pat (require_name:{})",
@@ -1542,12 +1507,13 @@ impl<'a> Parser<'a> {
     /// Matches token_lit = LIT_INTEGER | ...
     pub fn parse_lit_token(&mut self) -> PResult<'a, LitKind> {
         let out = match self.token {
-            token::Interpolated(token::NtExpr(ref v)) => {
-                match v.node {
+            token::Interpolated(ref nt) => match **nt {
+                token::NtExpr(ref v) => match v.node {
                     ExprKind::Lit(ref lit) => { lit.node.clone() }
                     _ => { return self.unexpected_last(&self.token); }
-                }
-            }
+                },
+                _ => { return self.unexpected_last(&self.token); }
+            },
             token::Literal(lit, suf) => {
                 let (suffix_illegal, out) = match lit {
                     token::Byte(i) => (true, LitKind::Byte(parse::byte_lit(&i.as_str()).0)),
@@ -1703,14 +1669,7 @@ impl<'a> Parser<'a> {
     /// bounds are permitted and whether `::` must precede type parameter
     /// groups.
     pub fn parse_path(&mut self, mode: PathStyle) -> PResult<'a, ast::Path> {
-        // Check for a whole path...
-        let found = match self.token {
-            token::Interpolated(token::NtPath(_)) => Some(self.bump_and_get()),
-            _ => None,
-        };
-        if let Some(token::Interpolated(token::NtPath(path))) = found {
-            return Ok(*path);
-        }
+        maybe_whole!(self, NtPath, |x| x);
 
         let lo = self.span.lo;
         let is_global = self.eat(&token::ModSep);
@@ -2746,8 +2705,6 @@ impl<'a> Parser<'a> {
         // and token::SubstNt's; it's too early to know yet
         // whether something will be a nonterminal or a seq
         // yet.
-        maybe_whole!(deref self, NtTT);
-
         match self.token {
             token::Eof => {
                 let mut err: DiagnosticBuilder<'a> =
@@ -2760,6 +2717,17 @@ impl<'a> Parser<'a> {
                 Err(err)
             },
             token::OpenDelim(delim) => {
+                if self.tts.last().map(|&(_, i)| i == 1).unwrap_or(false) {
+                    let tt = self.tts.pop().unwrap().0;
+                    self.bump();
+                    return Ok(if self.allow_interpolated_tts {
+                        // avoid needlessly reparsing token trees in recursive macro expansions
+                        TokenTree::Token(tt.span(), token::Interpolated(Rc::new(token::NtTT(tt))))
+                    } else {
+                        tt
+                    });
+                }
+
                 let parsing_token_tree = ::std::mem::replace(&mut self.parsing_token_tree, true);
                 // The span for beginning of the delimited section
                 let pre_span = self.span;
@@ -2833,29 +2801,20 @@ impl<'a> Parser<'a> {
                     close_span: close_span,
                 })))
             },
+            token::CloseDelim(_) => {
+                // An unexpected closing delimiter (i.e., there is no
+                // matching opening delimiter).
+                let token_str = self.this_token_to_string();
+                let err = self.diagnostic().struct_span_err(self.span,
+                    &format!("unexpected close delimiter: `{}`", token_str));
+                Err(err)
+            },
+            /* we ought to allow different depths of unquotation */
+            token::Dollar | token::SubstNt(..) if self.quote_depth > 0 => {
+                self.parse_unquoted()
+            }
             _ => {
-                // invariants: the current token is not a left-delimiter,
-                // not an EOF, and not the desired right-delimiter (if
-                // it were, parse_seq_to_before_end would have prevented
-                // reaching this point).
-                maybe_whole!(deref self, NtTT);
-                match self.token {
-                    token::CloseDelim(_) => {
-                        // An unexpected closing delimiter (i.e., there is no
-                        // matching opening delimiter).
-                        let token_str = self.this_token_to_string();
-                        let err = self.diagnostic().struct_span_err(self.span,
-                            &format!("unexpected close delimiter: `{}`", token_str));
-                        Err(err)
-                    },
-                    /* we ought to allow different depths of unquotation */
-                    token::Dollar | token::SubstNt(..) if self.quote_depth > 0 => {
-                        self.parse_unquoted()
-                    }
-                    _ => {
-                        Ok(TokenTree::Token(self.span, self.bump_and_get()))
-                    }
-                }
+                Ok(TokenTree::Token(self.span, self.bump_and_get()))
             }
         }
     }
@@ -3336,7 +3295,7 @@ impl<'a> Parser<'a> {
     }
 
     pub fn parse_arm(&mut self) -> PResult<'a, Arm> {
-        maybe_whole!(no_clone self, NtArm);
+        maybe_whole!(self, NtArm, |x| x);
 
         let attrs = self.parse_outer_attributes()?;
         let pats = self.parse_pats()?;
@@ -3592,7 +3551,7 @@ impl<'a> Parser<'a> {
 
     /// Parse a pattern.
     pub fn parse_pat(&mut self) -> PResult<'a, P<Pat>> {
-        maybe_whole!(self, NtPat);
+        maybe_whole!(self, NtPat, |x| x);
 
         let lo = self.span.lo;
         let pat;
@@ -3897,7 +3856,7 @@ impl<'a> Parser<'a> {
     fn parse_stmt_without_recovery(&mut self,
                                    macro_legacy_warnings: bool)
                                    -> PResult<'a, Option<Stmt>> {
-        maybe_whole!(Some deref self, NtStmt);
+        maybe_whole!(self, NtStmt, |x| Some(x));
 
         let attrs = self.parse_outer_attributes()?;
         let lo = self.span.lo;
@@ -4086,7 +4045,7 @@ impl<'a> Parser<'a> {
 
     /// Parse a block. No inner attrs are allowed.
     pub fn parse_block(&mut self) -> PResult<'a, P<Block>> {
-        maybe_whole!(no_clone self, NtBlock);
+        maybe_whole!(self, NtBlock, |x| x);
 
         let lo = self.span.lo;
 
@@ -4124,7 +4083,7 @@ impl<'a> Parser<'a> {
 
     /// Parse a block. Inner attrs are allowed.
     fn parse_inner_attrs_and_block(&mut self) -> PResult<'a, (Vec<Attribute>, P<Block>)> {
-        maybe_whole!(pair_empty self, NtBlock);
+        maybe_whole!(self, NtBlock, |x| (Vec::new(), x));
 
         let lo = self.span.lo;
         self.expect(&token::OpenDelim(token::Brace))?;
@@ -4299,7 +4258,7 @@ impl<'a> Parser<'a> {
     ///                  | ( < lifetimes , typaramseq ( , )? > )
     /// where   typaramseq = ( typaram ) | ( typaram , typaramseq )
     pub fn parse_generics(&mut self) -> PResult<'a, ast::Generics> {
-        maybe_whole!(self, NtGenerics);
+        maybe_whole!(self, NtGenerics, |x| x);
         let span_lo = self.span.lo;
 
         if self.eat(&token::Lt) {
@@ -4440,7 +4399,7 @@ impl<'a> Parser<'a> {
     /// where T : Trait<U, V> + 'b, 'a : 'b
     /// ```
     pub fn parse_where_clause(&mut self) -> PResult<'a, ast::WhereClause> {
-        maybe_whole!(self, NtWhereClause);
+        maybe_whole!(self, NtWhereClause, |x| x);
 
         let mut where_clause = WhereClause {
             id: ast::DUMMY_NODE_ID,
@@ -4848,7 +4807,7 @@ impl<'a> Parser<'a> {
 
     /// Parse an impl item.
     pub fn parse_impl_item(&mut self) -> PResult<'a, ImplItem> {
-        maybe_whole!(no_clone_from_p self, NtImplItem);
+        maybe_whole!(self, NtImplItem, |x| x);
 
         let mut attrs = self.parse_outer_attributes()?;
         let lo = self.span.lo;
@@ -5716,19 +5675,13 @@ impl<'a> Parser<'a> {
     /// extern crate.
     fn parse_item_(&mut self, attrs: Vec<Attribute>,
                    macros_allowed: bool, attributes_allowed: bool) -> PResult<'a, Option<P<Item>>> {
-        let nt_item = match self.token {
-            token::Interpolated(token::NtItem(ref item)) => {
-                Some((**item).clone())
-            }
-            _ => None
-        };
-        if let Some(mut item) = nt_item {
-            self.bump();
+        maybe_whole!(self, NtItem, |item| {
+            let mut item = item.unwrap();
             let mut attrs = attrs;
             mem::swap(&mut item.attrs, &mut attrs);
             item.attrs.extend(attrs);
-            return Ok(Some(P(item)));
-        }
+            Some(P(item))
+        });
 
         let lo = self.span.lo;
 
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 4d0da660302..0198ee073d2 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -123,7 +123,7 @@ pub enum Token {
     Lifetime(ast::Ident),
 
     /* For interpolation */
-    Interpolated(Nonterminal),
+    Interpolated(Rc<Nonterminal>),
     // Can be expanded into several tokens.
     /// Doc comment
     DocComment(ast::Name),
@@ -172,12 +172,15 @@ impl Token {
             DotDot | DotDotDot          => true, // range notation
             Lt | BinOp(Shl)             => true, // associated path
             ModSep                      => true,
-            Interpolated(NtExpr(..))    => true,
-            Interpolated(NtIdent(..))   => true,
-            Interpolated(NtBlock(..))   => true,
-            Interpolated(NtPath(..))    => true,
             Pound                       => true, // for expression attributes
-            _                           => false,
+            Interpolated(ref nt) => match **nt {
+                NtExpr(..) => true,
+                NtIdent(..) => true,
+                NtBlock(..) => true,
+                NtPath(..) => true,
+                _ => false,
+            },
+            _ => false,
         }
     }
 
@@ -215,10 +218,12 @@ impl Token {
 
     /// Returns `true` if the token is an interpolated path.
     pub fn is_path(&self) -> bool {
-        match *self {
-            Interpolated(NtPath(..))    => true,
-            _                           => false,
+        if let Interpolated(ref nt) = *self {
+            if let NtPath(..) = **nt {
+                return true;
+            }
         }
+        false
     }
 
     /// Returns `true` if the token is a lifetime.
@@ -290,19 +295,19 @@ impl Token {
 pub enum Nonterminal {
     NtItem(P<ast::Item>),
     NtBlock(P<ast::Block>),
-    NtStmt(P<ast::Stmt>),
+    NtStmt(ast::Stmt),
     NtPat(P<ast::Pat>),
     NtExpr(P<ast::Expr>),
     NtTy(P<ast::Ty>),
-    NtIdent(Box<ast::SpannedIdent>),
+    NtIdent(ast::SpannedIdent),
     /// Stuff inside brackets for attributes
     NtMeta(P<ast::MetaItem>),
-    NtPath(Box<ast::Path>),
-    NtTT(P<tokenstream::TokenTree>), // needs P'ed to break a circularity
+    NtPath(ast::Path),
+    NtTT(tokenstream::TokenTree),
     // These are not exposed to macros, but are used by quasiquote.
     NtArm(ast::Arm),
-    NtImplItem(P<ast::ImplItem>),
-    NtTraitItem(P<ast::TraitItem>),
+    NtImplItem(ast::ImplItem),
+    NtTraitItem(ast::TraitItem),
     NtGenerics(ast::Generics),
     NtWhereClause(ast::WhereClause),
     NtArg(ast::Arg),
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index b0bd6446743..7352792a8a2 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -285,7 +285,7 @@ pub fn token_to_string(tok: &Token) -> String {
         token::Comment              => "/* */".to_string(),
         token::Shebang(s)           => format!("/* shebang: {}*/", s),
 
-        token::Interpolated(ref nt) => match *nt {
+        token::Interpolated(ref nt) => match **nt {
             token::NtExpr(ref e)        => expr_to_string(&e),
             token::NtMeta(ref e)        => meta_item_to_string(&e),
             token::NtTy(ref e)          => ty_to_string(&e),
diff --git a/src/libsyntax/tokenstream.rs b/src/libsyntax/tokenstream.rs
index 9e644e59e86..9ef6c07e489 100644
--- a/src/libsyntax/tokenstream.rs
+++ b/src/libsyntax/tokenstream.rs
@@ -134,8 +134,10 @@ impl TokenTree {
                     AttrStyle::Inner => 3,
                 }
             }
+            TokenTree::Token(_, token::Interpolated(ref nt)) => {
+                if let Nonterminal::NtTT(..) = **nt { 1 } else { 0 }
+            },
             TokenTree::Token(_, token::MatchNt(..)) => 3,
-            TokenTree::Token(_, token::Interpolated(Nonterminal::NtTT(..))) => 1,
             TokenTree::Delimited(_, ref delimed) => delimed.tts.len() + 2,
             TokenTree::Sequence(_, ref seq) => seq.tts.len(),
             TokenTree::Token(..) => 0,
@@ -193,9 +195,6 @@ impl TokenTree {
                          TokenTree::Token(sp, token::Ident(kind))];
                 v[index].clone()
             }
-            (&TokenTree::Token(_, token::Interpolated(Nonterminal::NtTT(ref tt))), _) => {
-                tt.clone().unwrap()
-            }
             (&TokenTree::Sequence(_, ref seq), _) => seq.tts[index].clone(),
             _ => panic!("Cannot expand a token tree"),
         }
@@ -215,11 +214,9 @@ impl TokenTree {
                  mtch: &[TokenTree],
                  tts: &[TokenTree])
                  -> macro_parser::NamedParseResult {
+        let diag = &cx.parse_sess().span_diagnostic;
         // `None` is because we're not interpolating
-        let arg_rdr = lexer::new_tt_reader_with_doc_flag(&cx.parse_sess().span_diagnostic,
-                                                         None,
-                                                         tts.iter().cloned().collect(),
-                                                         true);
+        let arg_rdr = lexer::new_tt_reader(diag, None, tts.iter().cloned().collect());
         macro_parser::parse(cx.parse_sess(), arg_rdr, mtch)
     }