     return base if not props and base instanceof Value
     @base       = base
     @properties = props or []
-    @tags       = if tag then {(tag): on} else {}
+    @[tag]      = true if tag
 
   # Add a property access to the list.
   push: (prop) ->

  constructor: (@body, head) ->
    if head.index instanceof Value
      throw SyntaxError 'index cannot be a pattern matching expression'
    super()
    extend this, head
    @step  or= new Literal 1 unless @object
    @pattern = @name instanceof Value

      else
        ',\n'
      indent = if prop instanceof Comment then '' else idt
      if prop instanceof Value and prop.this
        prop = new Assign prop.properties[0].name, prop, 'object'
      else if prop not instanceof Assign and prop not instanceof Comment
        prop = new Assign prop, prop, 'object'
