231 

   232 class basealiasrules(object):

   233     """Parsing and expansion rule set of aliases

   234 

   235     This is a helper for fileset/revset/template aliases. A concrete rule set

   236     should be made by sub-classing this and implementing class/static methods.

   237 

   238     It supports alias expansion of symbol and funciton-call styles::

   239 

   240         # decl = defn

   241         h = heads(default)

   242         b($1) = ancestors($1) - ancestors(default)

   243     """

   244     # typically a config section, which will be included in error messages

   245     _section = None

   246     # tags of symbol and function nodes

   247     _symbolnode = 'symbol'

   248     _funcnode = 'func'

   249 

   250     def __new__(cls):

   251         raise TypeError("'%s' is not instantiatable" % cls.__name__)

   252 

   253     @staticmethod

   254     def _parsedecl(spec):

   255         """Parse an alias name and arguments"""

   256         raise NotImplementedError

   257 

   258     @staticmethod

   259     def _parsedefn(spec):

   260         """Parse an alias definition"""

   261         raise NotImplementedError

   262 

   263     @staticmethod

   264     def _getlist(tree):

   265         """Extract a list of arguments from parsed tree"""

   266         raise NotImplementedError