Issue #1354, 'in' with splatted arrays.

Author: jashkenas

lib/nodes.js

@@ -1355,7 +1355,9 @@ exports.In = class In extends Base
   invert: NEGATE
 
   compileNode: (o) ->
-    if @array instanceof Value and @array.isArray()
+    isArray = @array instanceof Value and @array.isArray()
+    splat   = obj for obj in @array.base.objects when obj instanceof Splat if isArray
+    if isArray and not splat
       @compileOrTest o
     else
       @compileLoopTest o

src/nodes.coffee

@@ -187,6 +187,10 @@ test "#768: `in` should preserve evaluation order", ->
 test "#1099: empty array after `in` should compile to `false`", ->
   eq 1, [5 in []].length
   eq false, do -> return 0 in []
+  
+test "#1354: optimized `in` checks should not happen when splats are present", ->
+  a = [6, 9]
+  eq 9 in [3, a...], true
 
 
 # Chained Comparison