From b26c6221f1b0e2b1a9afbc9aa3745477a81fd97b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=BCrg=20Lehni?= <juerg@scratchdisk.com>
Date: Mon, 15 Jun 2015 23:43:03 +0200
Subject: [PATCH] Fix PaperScript increment operator in rare special case.

Closes #691.
---
 src/core/PaperScript.js | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/src/core/PaperScript.js b/src/core/PaperScript.js
index 09843b9a..693616b7 100644
--- a/src/core/PaperScript.js
+++ b/src/core/PaperScript.js
@@ -225,15 +225,22 @@ Base.exports.PaperScript = (function() {
                         || parentType === 'MemberExpression' && parent.computed
                 )) {
                     if (node.type === 'UpdateExpression') {
-                        var arg = getCode(node.argument);
-                        var str = arg + ' = __$__(' + arg
-                                + ', "' + node.operator[0] + '", 1)';
+                        var arg = getCode(node.argument),
+                            exp = '__$__(' + arg + ', "' + node.operator[0]
+                                    + '", 1)',
+                            str = arg + ' = ' + exp;
                         // If this is not a prefixed update expression
                         // (++a, --a), assign the old value before updating it.
                         if (!node.prefix
                                 && (parentType === 'AssignmentExpression'
-                                    || parentType === 'VariableDeclarator'))
+                                    || parentType === 'VariableDeclarator')) {
+                            // Handle special issue #691 where the old value is
+                            // assigned to itself, and the expression is just
+                            // executed after, e.g.: `var x = ***; x = x++;`
+                            if (getCode(parent.left || parent.id) === arg)
+                                str = exp;
                             str = arg + '; ' + str;
+                        }
                         replaceCode(node, str);
                     } else { // AssignmentExpression
                         if (/^.=$/.test(node.operator)