From 0217ed55055928cee4a13927c646745e4fdcceab Mon Sep 17 00:00:00 2001
From: zdenko <zdenko.vujasinovic@gmail.com>
Date: Tue, 16 Jan 2018 05:03:01 +0100
Subject: [PATCH] Fix #1726: expression in property access causes unexpected
 results (#4851)

* fix #1726

* Explain what's happening, rather than just linking to an issue

* Updated output

* Optimization
---
 lib/coffeescript/nodes.js        | 14 ++++++++++----
 src/nodes.coffee                 |  8 ++++++--
 test/slicing_and_splicing.coffee |  6 ++++++
 3 files changed, 22 insertions(+), 6 deletions(-)

diff --git a/lib/coffeescript/nodes.js b/lib/coffeescript/nodes.js
index 504a5333..4a1876ef 100644
--- a/lib/coffeescript/nodes.js
+++ b/lib/coffeescript/nodes.js
@@ -849,7 +849,7 @@
             // generates output indented by two spaces; so all we need to do is
             // search for a `code` property that begins with at least two spaces.
             fragmentIndent = '';
-            ref1 = fragments.slice(0, fragmentIndex + 1);
+            ref1 = fragments.slice(0, (fragmentIndex + 1));
             for (k = ref1.length - 1; k >= 0; k += -1) {
               pastFragment = ref1[k];
               indent = /^ {2,}/m.exec(pastFragment.code);
@@ -874,7 +874,7 @@
               }
               return results;
             })()).join(`\n${fragmentIndent}`).replace(/^(\s*)$/gm, '');
-            ref2 = fragments.slice(0, fragmentIndex + 1);
+            ref2 = fragments.slice(0, (fragmentIndex + 1));
             for (pastFragmentIndex = l = ref2.length - 1; l >= 0; pastFragmentIndex = l += -1) {
               pastFragment = ref2[pastFragmentIndex];
               newLineIndex = pastFragment.code.lastIndexOf('\n');
@@ -2097,8 +2097,14 @@
       compileNode(o) {
         var compiled, compiledText, from, fromCompiled, to, toStr;
         ({to, from} = this.range);
-        fromCompiled = from && from.compileToFragments(o, LEVEL_PAREN) || [this.makeCode('0')];
-        // TODO: jwalton - move this into the 'if'?
+        // Handle an expression in the property access, e.g. `a[!b in c..]`.
+        if (from != null ? from.shouldCache() : void 0) {
+          from = new Value(new Parens(from));
+        }
+        if (to != null ? to.shouldCache() : void 0) {
+          to = new Value(new Parens(to));
+        }
+        fromCompiled = (from != null ? from.compileToFragments(o, LEVEL_PAREN) : void 0) || [this.makeCode('0')];
         if (to) {
           compiled = to.compileToFragments(o, LEVEL_PAREN);
           compiledText = fragmentsToText(compiled);
diff --git a/src/nodes.coffee b/src/nodes.coffee
index 8ca12ee9..7a459a4b 100644
--- a/src/nodes.coffee
+++ b/src/nodes.coffee
@@ -1406,8 +1406,12 @@ exports.Slice = class Slice extends Base
   # `9e9` should be safe because `9e9` > `2**32`, the max array length.
   compileNode: (o) ->
     {to, from} = @range
-    fromCompiled = from and from.compileToFragments(o, LEVEL_PAREN) or [@makeCode '0']
-    # TODO: jwalton - move this into the 'if'?
+    # Handle an expression in the property access, e.g. `a[!b in c..]`.
+    if from?.shouldCache()
+      from = new Value new Parens from
+    if to?.shouldCache()
+      to = new Value new Parens to
+    fromCompiled = from?.compileToFragments(o, LEVEL_PAREN) or [@makeCode '0']
     if to
       compiled     = to.compileToFragments o, LEVEL_PAREN
       compiledText = fragmentsToText compiled
diff --git a/test/slicing_and_splicing.coffee b/test/slicing_and_splicing.coffee
index 65bd3485..ffbabc66 100644
--- a/test/slicing_and_splicing.coffee
+++ b/test/slicing_and_splicing.coffee
@@ -165,3 +165,9 @@ test "#2953: methods on endpoints in assignment from array splice literal", ->
   delete Number.prototype.same
 
   arrayEq [0, 5, 9], list
+
+test "#1726: `Op` expression in property access causes unexpected results", ->
+  a = [0..2]
+  arrayEq a, a[(!1 in a)..]
+  arrayEq a, a[!1 in a..]
+  arrayEq a[(!1 in a)..], a[(!1 in a)..]