Added generator for custom free variable types, e.g., '_cache',

'_cache2', and so on.

lib/scope.js

@@ -58,14 +58,25 @@
       }
       return !!(this.parent && this.parent.check(name));
     };
-    Scope.prototype.freeVariable = function() {
-      var ordinal;
-      while (this.check(this.tempVars.general)) {
-        ordinal = 1 + parseInt(this.tempVars.general.substr(1), 36);
-        this.tempVars.general = '_' + ordinal.toString(36).replace(/\d/g, 'a');
+    Scope.prototype.freeVariable = function(type) {
+      var next;
+      if (type) {
+        next = function(prev) {
+          return '_' + type + ((prev && Number(prev.match(/\d+$/) || 1) + 1) || '');
+        };
+      } else {
+        type = 'general';
+        next = function(prev) {
+          var ordinal;
+          ordinal = 1 + parseInt(prev.substr(1), 36);
+          return '_' + ordinal.toString(36).replace(/\d/g, 'a');
+        };
       }
-      this.variables[this.tempVars.general] = 'var';
-      return this.tempVars.general;
+      while (this.check(this.tempVars[type] || (this.tempVars[type] = next()))) {
+        this.tempVars[type] = next(this.tempVars[type]);
+      }
+      this.variables[this.tempVars[type]] = 'var';
+      return this.tempVars[type];
     };
     Scope.prototype.assign = function(name, value) {
       return (this.variables[name] = {

src/scope.coffee

@@ -54,12 +54,19 @@ exports.Scope = class Scope
 
   # If we need to store an intermediate result, find an available name for a
   # compiler-generated variable. `_a`, `_b`, and so on...
-  freeVariable: ->
-    while @check @tempVars.general
-      ordinal = 1 + parseInt @tempVars.general.substr(1), 36
-      @tempVars.general = '_' + ordinal.toString(36).replace(/\d/g, 'a')
-    @variables[@tempVars.general] = 'var'
-    @tempVars.general
+  freeVariable: (type) ->
+    if type
+      next = (prev) ->
+        '_' + type + ((prev and Number(prev.match(/\d+$/) or 1) + 1) or '')
+    else
+      type = 'general'
+      next = (prev) ->
+        ordinal = 1 + parseInt prev.substr(1), 36
+        '_' + ordinal.toString(36).replace /\d/g, 'a'
+    while @check @tempVars[type] or= next()
+      @tempVars[type] = next @tempVars[type]
+    @variables[@tempVars[type]] = 'var'
+    @tempVars[type]
 
   # Ensure that an assignment is made at the top of this scope
   # (or at the top-level scope, if requested).