syntax: Allow 1-tuple expressions

This is for greater uniformity (for example, macros that generate
tuples). rustc already supported 1-tuple patterns, but there was no
way to construct a 1-tuple term.

1 files changed, 17 insertions, 6 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 799f0d40a46..b5c68d6715e 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -1061,6 +1061,9 @@ pub impl Parser {
 
         if self.token == token::LPAREN {
             self.bump();
+            // (e) is parenthesized e
+            // (e,) is a tuple with only one field, e
+            let mut one_tuple = false;
             if self.token == token::RPAREN {
                 hi = self.span.hi;
                 self.bump();
@@ -1069,12 +1072,18 @@ pub impl Parser {
             }
             let mut es = ~[self.parse_expr()];
             while self.token == token::COMMA {
-                self.bump(); es.push(self.parse_expr());
+                self.bump();
+                if self.token != token::RPAREN {
+                    es.push(self.parse_expr());
+                }
+                else {
+                    one_tuple = true;
+                }
             }
             hi = self.span.hi;
             self.expect(token::RPAREN);
 
-            return if es.len() == 1 {
+            return if es.len() == 1 && !one_tuple {
                 self.mk_expr(lo, self.span.hi, expr_paren(es[0]))
             }
             else {
@@ -2158,11 +2167,13 @@ pub impl Parser {
                 pat = pat_lit(expr);
             } else {
                 let mut fields = ~[self.parse_pat(refutable)];
-                while self.token == token::COMMA {
-                    self.bump();
-                    fields.push(self.parse_pat(refutable));
+                if self.look_ahead(1) != token::RPAREN {
+                    while self.token == token::COMMA {
+                        self.bump();
+                        fields.push(self.parse_pat(refutable));
+                    }
                 }
-                if vec::len(fields) == 1u { self.expect(token::COMMA); }
+                if fields.len() == 1 { self.expect(token::COMMA); }
                 hi = self.span.hi;
                 self.expect(token::RPAREN);
                 pat = pat_tup(fields);