From b51118c3fcd05cbd0cce58826f4c561a3a57e3d3 Mon Sep 17 00:00:00 2001
From: Charlie Somerville <charlie@charliesomerville.com>
Date: Sun, 18 Jan 2015 00:42:43 +1100
Subject: [PATCH] use right recursion for right associative operators

---
 acorn.js | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/acorn.js b/acorn.js
index a3be8bdb90..3cf3f06e87 100644
--- a/acorn.js
+++ b/acorn.js
@@ -2515,9 +2515,17 @@
         var op = tokType;
         next();
         var start = storeCurrentPos();
-        node.right = parseExprOp(parseMaybeUnary(), start, prec, noIn);
+        if(op.rightAssociative) {
+          node.right = parseExprOp(parseMaybeUnary(), start, prec - 1, noIn);
+        } else {
+          node.right = parseExprOp(parseMaybeUnary(), start, prec, noIn);
+        }
         finishNode(node, (op === _logicalOR || op === _logicalAND) ? "LogicalExpression" : "BinaryExpression");
-        return parseExprOp(node, leftStart, minPrec, noIn);
+        if(op.rightAssociative) {
+          return node;
+        } else {
+          return parseExprOp(node, leftStart, minPrec, noIn);
+        }
       }
     }
     return left;