added test for lexical scope sharing through generated closure wrappers, something uncommonly used, but that was a regression

lib/coffee_script/nodes.rb

@@ -55,10 +55,11 @@ module CoffeeScript
       closure  ? compile_closure(@options) : compile_node(@options)
     end
 
+    # Statements converted into expressions share scope with their parent
+    # closure, to preserve JavaScript-style lexical scope.
     def compile_closure(o={})
-      indent     = o[:indent]
-      @indent    = (o[:indent] = idt(1))
-      ClosureNode.wrap(self).compile(o)
+      @indent = o[:indent]
+      ClosureNode.wrap(self).compile(o.merge(:shared_scope => o[:scope]))
     end
 
     # Quick short method for the current indentation level, plus tabbing in.

test/fixtures/execution/test_existence.coffee

@@ -51,4 +51,5 @@ arr: ["--", "----"]
 print(arr.pop()?.length is 4)
 print(arr.pop()?.length is 2)
 print(arr.pop()?.length is undefined)
+print(arr[0]?.length is undefined)
 print(arr.pop()?.length?.non?.existent()?.property is undefined)

test/fixtures/execution/test_lexical_scope.coffee

@@ -1,3 +1,10 @@
 num: 1 + 2 + (a: 3)
 
-print(num is 6)
+print(num is 6)
+
+
+result: if true
+  false
+  other: "result"
+
+print(result is "result" and other is "result")