Use common variants for open and close delimiters

This common representation for delimeters should make pattern matching easier. Having a separate `token::DelimToken` enum also allows us to enforce the invariant that the opening and closing delimiters must be the same in `ast::TtDelimited`, removing the need to ensure matched delimiters when working with token trees.

5 files changed, 34 insertions, 31 deletions

diff --git a/src/libsyntax/ext/asm.rs b/src/libsyntax/ext/asm.rs
index 2b52b7feacc..d57d6e52d7f 100644
--- a/src/libsyntax/ext/asm.rs
+++ b/src/libsyntax/ext/asm.rs
@@ -84,9 +84,9 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
 
                     let span = p.last_span;
 
-                    p.expect(&token::LParen);
+                    p.expect(&token::OpenDelim(token::Paren));
                     let out = p.parse_expr();
-                    p.expect(&token::RParen);
+                    p.expect(&token::CloseDelim(token::Paren));
 
                     // Expands a read+write operand into two operands.
                     //
@@ -129,9 +129,9 @@ pub fn expand_asm<'cx>(cx: &'cx mut ExtCtxt, sp: Span, tts: &[ast::TokenTree])
                         cx.span_err(p.last_span, "input operand constraint contains '+'");
                     }
 
-                    p.expect(&token::LParen);
+                    p.expect(&token::OpenDelim(token::Paren));
                     let input = p.parse_expr();
-                    p.expect(&token::RParen);
+                    p.expect(&token::CloseDelim(token::Paren));
 
                     inputs.push((constraint, input));
                 }
diff --git a/src/libsyntax/ext/quote.rs b/src/libsyntax/ext/quote.rs
index a95a737720a..2151f79cd7b 100644
--- a/src/libsyntax/ext/quote.rs
+++ b/src/libsyntax/ext/quote.rs
@@ -531,6 +531,15 @@ fn mk_binop(cx: &ExtCtxt, sp: Span, bop: token::BinOpToken) -> P<ast::Expr> {
     mk_token_path(cx, sp, name)
 }
 
+fn mk_delim(cx: &ExtCtxt, sp: Span, delim: token::DelimToken) -> P<ast::Expr> {
+    let name = match delim {
+        token::Paren     => "Paren",
+        token::Bracket   => "Bracket",
+        token::Brace     => "Brace",
+    };
+    mk_token_path(cx, sp, name)
+}
+
 #[allow(non_uppercase_statics)] // NOTE(stage0): remove this attribute after the next snapshot
 fn mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
     match *tok {
@@ -542,6 +551,15 @@ fn mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
                                 vec!(mk_binop(cx, sp, binop)));
         }
 
+        token::OpenDelim(delim) => {
+            return cx.expr_call(sp, mk_token_path(cx, sp, "OpenDelim"),
+                                vec![mk_delim(cx, sp, delim)]);
+        }
+        token::CloseDelim(delim) => {
+            return cx.expr_call(sp, mk_token_path(cx, sp, "CloseDelim"),
+                                vec![mk_delim(cx, sp, delim)]);
+        }
+
         token::LitByte(i) => {
             let e_byte = mk_name(cx, sp, i.ident());
 
@@ -625,12 +643,6 @@ fn mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
         token::RArrow       => "RArrow",
         token::LArrow       => "LArrow",
         token::FatArrow     => "FatArrow",
-        token::LParen       => "LParen",
-        token::RParen       => "RParen",
-        token::LBracket     => "LBracket",
-        token::RBracket     => "RBracket",
-        token::LBrace       => "LBrace",
-        token::RBrace       => "RBrace",
         token::Pound        => "Pound",
         token::Dollar       => "Dollar",
         token::Underscore   => "Underscore",
@@ -640,7 +652,6 @@ fn mk_token(cx: &ExtCtxt, sp: Span, tok: &token::Token) -> P<ast::Expr> {
     mk_token_path(cx, sp, name)
 }
 
-
 fn mk_tt(cx: &ExtCtxt, _: Span, tt: &ast::TokenTree) -> Vec<P<ast::Stmt>> {
     match *tt {
         ast::TtToken(sp, ref tok) => {
@@ -656,10 +667,9 @@ fn mk_tt(cx: &ExtCtxt, _: Span, tt: &ast::TokenTree) -> Vec<P<ast::Stmt>> {
             vec!(cx.stmt_expr(e_push))
         },
         ast::TtDelimited(sp, ref delimed) => {
-            let (ref open, ref tts, ref close) = **delimed;
-            mk_tt(cx, sp, &open.to_tt()).into_iter()
-                .chain(tts.iter().flat_map(|tt| mk_tt(cx, sp, tt).into_iter()))
-                .chain(mk_tt(cx, sp, &close.to_tt()).into_iter())
+            mk_tt(cx, sp, &delimed.open_tt()).into_iter()
+                .chain(delimed.tts.iter().flat_map(|tt| mk_tt(cx, sp, tt).into_iter()))
+                .chain(mk_tt(cx, sp, &delimed.close_tt()).into_iter())
                 .collect()
         },
         ast::TtSequence(..) => panic!("TtSequence in quote!"),
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 9260a45adb9..bbc2cb86d00 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -355,10 +355,8 @@ pub fn parse(sess: &ParseSess,
                     // Built-in nonterminals never start with these tokens,
                     // so we can eliminate them from consideration.
                     match tok {
-                        token::RParen |
-                        token::RBrace |
-                        token::RBracket => {},
-                        _ => bb_eis.push(ei)
+                        token::CloseDelim(_) => {},
+                        _ => bb_eis.push(ei),
                     }
                   }
                   MatchTok(ref t) => {
diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 85bd5cde304..e50d4457af2 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -172,10 +172,7 @@ fn generic_extension<'cx>(cx: &'cx ExtCtxt,
                     MatchedNonterminal(NtTT(ref tt)) => {
                         match **tt {
                             // ignore delimiters
-                            TtDelimited(_, ref delimed) => {
-                                let (_, ref tts, _) = **delimed;
-                                tts.clone()
-                            },
+                            TtDelimited(_, ref delimed) => delimed.tts.clone(),
                             _ => cx.span_fatal(sp, "macro rhs must be delimited"),
                         }
                     },
diff --git a/src/libsyntax/ext/tt/transcribe.rs b/src/libsyntax/ext/tt/transcribe.rs
index 2c7b583d460..249a985a648 100644
--- a/src/libsyntax/ext/tt/transcribe.rs
+++ b/src/libsyntax/ext/tt/transcribe.rs
@@ -129,8 +129,7 @@ impl Add<LockstepIterSize, LockstepIterSize> for LockstepIterSize {
 fn lockstep_iter_size(t: &TokenTree, r: &TtReader) -> LockstepIterSize {
     match *t {
         TtDelimited(_, ref delimed) => {
-            let (_, ref tts, _) = **delimed;
-            tts.iter().fold(LisUnconstrained, |size, tt| {
+            delimed.tts.iter().fold(LisUnconstrained, |size, tt| {
                 size + lockstep_iter_size(tt, r)
             })
         },
@@ -207,14 +206,13 @@ pub fn tt_next_token(r: &mut TtReader) -> TokenAndSpan {
         };
         match t {
             TtDelimited(_, ref delimed) => {
-                let (ref open, ref tts, ref close) = **delimed;
-                let mut forest = Vec::with_capacity(1 + tts.len() + 1);
-                forest.push(open.to_tt());
-                forest.extend(tts.iter().map(|x| (*x).clone()));
-                forest.push(close.to_tt());
+                let mut tts = Vec::with_capacity(1 + delimed.tts.len() + 1);
+                tts.push(delimed.open_tt());
+                tts.extend(delimed.tts.iter().map(|tt| tt.clone()));
+                tts.push(delimed.close_tt());
 
                 r.stack.push(TtFrame {
-                    forest: Rc::new(forest),
+                    forest: Rc::new(tts),
                     idx: 0,
                     dotdotdoted: false,
                     sep: None