     new SourceNode(
       node.loc.start.line,
       node.loc.start.column,
-      'input.js',
+      @options.filename,
       output)
 
   ###

  ###

  onUnknownNode: (node, ctx) ->
    console.error node
    throw new Error("walk(): No handler for #{ctx?.type}")

  ###
  # visitors:


class Builder extends Walker

  constructor: (ast, options={}, @source) ->
    super
    @_indent = 0

