Fixes #2197 -- uncached double existential

lib/coffee-script/nodes.js

@@ -2193,7 +2193,7 @@
 
     Op.prototype.compileExistence = function(o) {
       var fst, ref;
-      if (this.first.isComplex() && o.level > LEVEL_TOP) {
+      if (this.first.isComplex()) {
         ref = new Literal(o.scope.freeVariable('ref'));
         fst = new Parens(new Assign(ref, this.first));
       } else {

src/nodes.coffee

@@ -1510,7 +1510,7 @@ exports.Op = class Op extends Base
     "(#{code})"
 
   compileExistence: (o) ->
-    if @first.isComplex() and o.level > LEVEL_TOP
+    if @first.isComplex()
       ref = new Literal o.scope.freeVariable 'ref'
       fst = new Parens new Assign ref, @first
     else

test/operators.coffee

@@ -274,4 +274,11 @@ test "#2155 ... conditional assignment to a closure", ->
   x = null
   func = -> x ?= (-> if true then 'hi')
   func()
-  eq x(), 'hi'
+  eq x(), 'hi'
+  
+test "#2197: Existential existential double trouble", ->
+  counter = 0
+  func = -> counter++
+  func()? ? 100
+  eq counter, 1
+