path: root/scoped_nodes.py

# copyright 2003-2013 LOGILAB S.A. (Paris, FRANCE), all rights reserved.
# contact http://www.logilab.fr/ -- mailto:contact@logilab.fr
#
# This file is part of astroid.
#
# astroid is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published by the
# Free Software Foundation, either version 2.1 of the License, or (at your
# option) any later version.
#
# astroid is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
# for more details.
#
# You should have received a copy of the GNU Lesser General Public License along
# with astroid. If not, see <http://www.gnu.org/licenses/>.
"""This module contains the classes for "scoped" node, i.e. which are opening a
new local scope in the language definition : Module, Class, Function (and
Lambda, GenExpr, DictComp and SetComp to some extent).
"""
from __future__ import with_statement

__doctype__ = "restructuredtext en"

import sys
from itertools import chain
try:
    from io import BytesIO
except ImportError:
    from cStringIO import StringIO as BytesIO

from logilab.common.compat import builtins
from logilab.common.decorators import cached, cachedproperty

from astroid.exceptions import NotFoundError, \
     AstroidBuildingException, InferenceError
from astroid.node_classes import Const, DelName, DelAttr, \
     Dict, From, List, Pass, Raise, Return, Tuple, Yield, YieldFrom, \
     LookupMixIn, const_factory as cf, unpack_infer, Name, CallFunc
from astroid.bases import NodeNG, InferenceContext, Instance,\
     YES, Generator, UnboundMethod, BoundMethod, _infer_stmts, copy_context, \
     BUILTINS
from astroid.mixins import FilterStmtsMixin
from astroid.bases import Statement
from astroid.manager import AstroidManager

ITER_METHODS = ('__iter__', '__getitem__')
PY3K = sys.version_info >= (3, 0)


def remove_nodes(func, cls):
    def wrapper(*args, **kwargs):
        nodes = [n for n in func(*args, **kwargs) if not isinstance(n, cls)]
        if not nodes:
            raise NotFoundError()
        return nodes
    return wrapper


def function_to_method(n, klass):
    if isinstance(n, Function):
        if n.type == 'classmethod':
            return BoundMethod(n, klass)
        if n.type != 'staticmethod':
            return UnboundMethod(n)
    return n

def std_special_attributes(self, name, add_locals=True):
    if add_locals:
        locals = self.locals
    else:
        locals = {}
    if name == '__name__':
        return [cf(self.name)] + locals.get(name, [])
    if name == '__doc__':
        return [cf(self.doc)] + locals.get(name, [])
    if name == '__dict__':
        return [Dict()] + locals.get(name, [])
    raise NotFoundError(name)

MANAGER = AstroidManager()
def builtin_lookup(name):
    """lookup a name into the builtin module
    return the list of matching statements and the astroid for the builtin
    module
    """
    builtin_astroid = MANAGER.ast_from_module(builtins)
    if name == '__dict__':
        return builtin_astroid, ()
    try:
        stmts = builtin_astroid.locals[name]
    except KeyError:
        stmts = ()
    return builtin_astroid, stmts


# TODO move this Mixin to mixins.py; problem: 'Function' in _scope_lookup
class LocalsDictNodeNG(LookupMixIn, NodeNG):
    """ this class provides locals handling common to Module, Function
    and Class nodes, including a dict like interface for direct access
    to locals information
    """

    # attributes below are set by the builder module or by raw factories

    # dictionary of locals with name as key and node defining the local as
    # value

    def qname(self):
        """return the 'qualified' name of the node, eg module.name,
        module.class.name ...
        """
        if self.parent is None:
            return self.name
        return '%s.%s' % (self.parent.frame().qname(), self.name)

    def frame(self):
        """return the first parent frame node (i.e. Module, Function or Class)
        """
        return self

    def scope(self):
        """return the first node defining a new scope (i.e. Module,
        Function, Class, Lambda but also GenExpr, DictComp and SetComp)
        """
        return self


    def _scope_lookup(self, node, name, offset=0):
        """XXX method for interfacing the scope lookup"""
        try:
            stmts = node._filter_stmts(self.locals[name], self, offset)
        except KeyError:
            stmts = ()
        if stmts:
            return self, stmts
        if self.parent: # i.e. not Module
            # nested scope: if parent scope is a function, that's fine
            # else jump to the module
            pscope = self.parent.scope()
            if not pscope.is_function:
                pscope = pscope.root()
            return pscope.scope_lookup(node, name)
        return builtin_lookup(name) # Module



    def set_local(self, name, stmt):
        """define <name> in locals (<stmt> is the node defining the name)
        if the node is a Module node (i.e. has globals), add the name to
        globals

        if the name is already defined, ignore it
        """
        #assert not stmt in self.locals.get(name, ()), (self, stmt)
        self.locals.setdefault(name, []).append(stmt)

    __setitem__ = set_local

    def _append_node(self, child):
        """append a child, linking it in the tree"""
        self.body.append(child)
        child.parent = self

    def add_local_node(self, child_node, name=None):
        """append a child which should alter locals to the given node"""
        if name != '__class__':
            # add __class__ node as a child will cause infinite recursion later!
            self._append_node(child_node)
        self.set_local(name or child_node.name, child_node)


    def __getitem__(self, item):
        """method from the `dict` interface returning the first node
        associated with the given name in the locals dictionary

        :type item: str
        :param item: the name of the locally defined object
        :raises KeyError: if the name is not defined
        """
        return self.locals[item][0]

    def __iter__(self):
        """method from the `dict` interface returning an iterator on
        `self.keys()`
        """
        return iter(self.keys())

    def keys(self):
        """method from the `dict` interface returning a tuple containing
        locally defined names
        """
        return self.locals.keys()

    def values(self):
        """method from the `dict` interface returning a tuple containing
        locally defined nodes which are instance of `Function` or `Class`
        """
        return [self[key] for key in self.keys()]

    def items(self):
        """method from the `dict` interface returning a list of tuple
        containing each locally defined name with its associated node,
        which is an instance of `Function` or `Class`
        """
        return zip(self.keys(), self.values())


    def __contains__(self, name):
        return name in self.locals
    has_key = __contains__

# Module  #####################################################################

class Module(LocalsDictNodeNG):
    _astroid_fields = ('body',)

    fromlineno = 0
    lineno = 0

    # attributes below are set by the builder module or by raw factories

    # the file from which as been extracted the astroid representation. It may
    # be None if the representation has been built from a built-in module
    file = None
    # Alternatively, if built from a string/bytes, this can be set
    file_bytes = None
    # encoding of python source file, so we can get unicode out of it (python2
    # only)
    file_encoding = None
    # the module name
    name = None
    # boolean for astroid built from source (i.e. ast)
    pure_python = None
    # boolean for package module
    package = None
    # dictionary of globals with name as key and node defining the global
    # as value
    globals = None

    # Future imports
    future_imports = None

    # names of python special attributes (handled by getattr impl.)
    special_attributes = set(('__name__', '__doc__', '__file__', '__path__',
                              '__dict__'))
    # names of module attributes available through the global scope
    scope_attrs = set(('__name__', '__doc__', '__file__', '__path__'))

    def __init__(self, name, doc, pure_python=True):
        self.name = name
        self.doc = doc
        self.pure_python = pure_python
        self.locals = self.globals = {}
        self.body = []
        self.future_imports = set()

    @property
    def file_stream(self):
        if self.file_bytes is not None:
            return BytesIO(self.file_bytes)
        if self.file is not None:
            return open(self.file, 'rb')
        return None

    def block_range(self, lineno):
        """return block line numbers.

        start from the beginning whatever the given lineno
        """
        return self.fromlineno, self.tolineno

    def scope_lookup(self, node, name, offset=0):
        if name in self.scope_attrs and not name in self.locals:
            try:
                return self, self.getattr(name)
            except NotFoundError:
                return self, ()
        return self._scope_lookup(node, name, offset)

    def pytype(self):
        return '%s.module' % BUILTINS

    def display_type(self):
        return 'Module'

    def getattr(self, name, context=None, ignore_locals=False):
        if name in self.special_attributes:
            if name == '__file__':
                return [cf(self.file)] + self.locals.get(name, [])
            if name == '__path__' and self.package:
                return [List()] + self.locals.get(name, [])
            return std_special_attributes(self, name)
        if not ignore_locals and name in self.locals:
            return self.locals[name]
        if self.package:
            try:
                return [self.import_module(name, relative_only=True)]
            except AstroidBuildingException:
                raise NotFoundError(name)
            except SyntaxError:
                raise NotFoundError(name)
            except Exception:# XXX pylint tests never pass here; do we need it?
                import traceback
                traceback.print_exc()
        raise NotFoundError(name)
    getattr = remove_nodes(getattr, DelName)

    def igetattr(self, name, context=None):
        """inferred getattr"""
        # set lookup name since this is necessary to infer on import nodes for
        # instance
        context = copy_context(context)
        context.lookupname = name
        try:
            return _infer_stmts(self.getattr(name, context), context, frame=self)
        except NotFoundError:
            raise InferenceError(name)

    def fully_defined(self):
        """return True if this module has been built from a .py file
        and so contains a complete representation including the code
        """
        return self.file is not None and self.file.endswith('.py')

    def statement(self):
        """return the first parent node marked as statement node
        consider a module as a statement...
        """
        return self

    def previous_sibling(self):
        """module has no sibling"""
        return

    def next_sibling(self):
        """module has no sibling"""
        return

    if sys.version_info < (2, 8):
        def absolute_import_activated(self):
            for stmt in self.locals.get('absolute_import', ()):
                if isinstance(stmt, From) and stmt.modname == '__future__':
                    return True
            return False
    else:
        absolute_import_activated = lambda self: True

    def import_module(self, modname, relative_only=False, level=None):
        """import the given module considering self as context"""
        if relative_only and level is None:
            level = 0
        absmodname = self.relative_to_absolute_name(modname, level)
        try:
            return MANAGER.ast_from_module_name(absmodname)
        except AstroidBuildingException:
            # we only want to import a sub module or package of this module,
            # skip here
            if relative_only:
                raise
        return MANAGER.ast_from_module_name(modname)

    def relative_to_absolute_name(self, modname, level):
        """return the absolute module name for a relative import.

        The relative import can be implicit or explicit.
        """
        # XXX this returns non sens when called on an absolute import
        # like 'pylint.checkers.astroid.utils'
        # XXX doesn't return absolute name if self.name isn't absolute name
        if self.absolute_import_activated() and level is None:
            return modname
        if level:
            if self.package:
                level = level - 1
            package_name = self.name.rsplit('.', level)[0]
        elif self.package:
            package_name = self.name
        else:
            package_name = self.name.rsplit('.', 1)[0]
        if package_name:
            if not modname:
                return package_name
            return '%s.%s' % (package_name, modname)
        return modname


    def wildcard_import_names(self):
        """return the list of imported names when this module is 'wildcard
        imported'

        It doesn't include the '__builtins__' name which is added by the
        current CPython implementation of wildcard imports.
        """
        # take advantage of a living module if it exists
        try:
            living = sys.modules[self.name]
        except KeyError:
            pass
        else:
            try:
                return living.__all__
            except AttributeError:
                return [name for name in living.__dict__.keys()
                        if not name.startswith('_')]
        # else lookup the astroid
        #
        # We separate the different steps of lookup in try/excepts
        # to avoid catching too many Exceptions
        # However, we can not analyse dynamically constructed __all__
        try:
            all = self['__all__']
        except KeyError:
            return [name for name in self.keys() if not name.startswith('_')]
        try:
            explicit = all.assigned_stmts().next()
        except InferenceError:
            return [name for name in self.keys() if not name.startswith('_')]
        except AttributeError:
            # not an assignment node
            # XXX infer?
            return [name for name in self.keys() if not name.startswith('_')]
        try:
            # should be a Tuple/List of constant string / 1 string not allowed
            return [const.value for const in explicit.elts]
        except AttributeError:
            return [name for name in self.keys() if not name.startswith('_')]


class ComprehensionScope(LocalsDictNodeNG):
    def frame(self):
        return self.parent.frame()

    scope_lookup = LocalsDictNodeNG._scope_lookup


class GenExpr(ComprehensionScope):
    _astroid_fields = ('elt', 'generators')

    def __init__(self):
        self.locals = {}
        self.elt = None
        self.generators = []


class DictComp(ComprehensionScope):
    _astroid_fields = ('key', 'value', 'generators')

    def __init__(self):
        self.locals = {}
        self.key = None
        self.value = None
        self.generators = []


class SetComp(ComprehensionScope):
    _astroid_fields = ('elt', 'generators')

    def __init__(self):
        self.locals = {}
        self.elt = None
        self.generators = []


class _ListComp(NodeNG):
    """class representing a ListComp node"""
    _astroid_fields = ('elt', 'generators')
    elt = None
    generators = None

if sys.version_info >= (3, 0):
    class ListComp(_ListComp, ComprehensionScope):
        """class representing a ListComp node"""
        def __init__(self):
            self.locals = {}
else:
    class ListComp(_ListComp):
        """class representing a ListComp node"""

# Function  ###################################################################

def _infer_decorator_callchain(node):
    """ Detect decorator call chaining and see if the
    end result is a static or a classmethod.
    """
    current = node
    while True:
        if isinstance(current, CallFunc):
            try:
                current = current.func.infer().next()
            except InferenceError:
                return
        elif isinstance(current, Function):
            if not current.parent:
                return
            try:
                # TODO: We don't handle multiple inference results right now,
                #       because there's no flow to reason when the return
                #       is what we are looking for, a static or a class method.
                result = current.infer_call_result(current.parent).next()
            except (StopIteration, InferenceError):
                return
            if isinstance(result, (Function, CallFunc)):
                current = result
            else:
                if isinstance(result, Instance):
                    result = result._proxied
                if isinstance(result, Class):
                    if (result.name == 'classmethod' and
                            result.root().name == BUILTINS):
                        return 'classmethod'
                    elif (result.name == 'staticmethod' and
                          result.root().name == BUILTINS):
                        return 'staticmethod'
                    else:
                        return
                else:
                    # We aren't interested in anything else returned,
                    # so go back to the function type inference.
                    return
        else:
            return

def _function_type(self):
    """
    Function type, possible values are:
    method, function, staticmethod, classmethod.
    """
    # Can't infer that this node is decorated
    # with a subclass of `classmethod` where `type` is first set,
    # so do it here.
    if self.decorators:
        for node in self.decorators.nodes:
            if isinstance(node, CallFunc):
                _type = _infer_decorator_callchain(node)
                if _type is None:
                    continue
                else:
                    return _type
            if not isinstance(node, Name):
                continue
            try:
                for infered in node.infer():
                    if not isinstance(infered, Class):
                        continue
                    for ancestor in infered.ancestors():
                        if isinstance(ancestor, Class):
                            if (ancestor.name == 'classmethod' and
                                    ancestor.root().name == BUILTINS):
                                return 'classmethod'
                            elif (ancestor.name == 'staticmethod' and
                                  ancestor.root().name == BUILTINS):
                                return 'staticmethod'
            except InferenceError:
                pass
    return self._type


class Lambda(LocalsDictNodeNG, FilterStmtsMixin):
    _astroid_fields = ('args', 'body',)
    name = '<lambda>'

    # function's type, 'function' | 'method' | 'staticmethod' | 'classmethod'
    type = 'function'

    def __init__(self):
        self.locals = {}
        self.args = []
        self.body = []

    def pytype(self):
        if 'method' in self.type:
            return '%s.instancemethod' % BUILTINS
        return '%s.function' % BUILTINS

    def display_type(self):
        if 'method' in self.type:
            return 'Method'
        return 'Function'

    def callable(self):
        return True

    def argnames(self):
        """return a list of argument names"""
        if self.args.args: # maybe None with builtin functions
            names = _rec_get_names(self.args.args)
        else:
            names = []
        if self.args.vararg:
            names.append(self.args.vararg)
        if self.args.kwarg:
            names.append(self.args.kwarg)
        return names

    def infer_call_result(self, caller, context=None):
        """infer what a function is returning when called"""
        return self.body.infer(context)

    def scope_lookup(self, node, name, offset=0):
        if node in self.args.defaults or node in self.args.kw_defaults:
            frame = self.parent.frame()
            # line offset to avoid that def func(f=func) resolve the default
            # value to the defined function
            offset = -1
        else:
            # check this is not used in function decorators
            frame = self
        return frame._scope_lookup(node, name, offset)


class Function(Statement, Lambda):
    if PY3K:
        _astroid_fields = ('decorators', 'args', 'body', 'returns')
        returns = None
    else:
        _astroid_fields = ('decorators', 'args', 'body')

    special_attributes = set(('__name__', '__doc__', '__dict__'))
    is_function = True
    # attributes below are set by the builder module or by raw factories
    blockstart_tolineno = None
    decorators = None
    _type = "function"
    type = cachedproperty(_function_type)

    def __init__(self, name, doc):
        self.locals = {}
        self.args = []
        self.body = []
        self.decorators = None
        self.name = name
        self.doc = doc
        self.extra_decorators = []
        self.instance_attrs = {}

    def set_line_info(self, lastchild):
        self.fromlineno = self.lineno
        # lineno is the line number of the first decorator, we want the def statement lineno
        if self.decorators is not None:
            self.fromlineno += sum(node.tolineno - node.lineno + 1
                                   for node in self.decorators.nodes)
        if self.args.fromlineno < self.fromlineno:
            self.args.fromlineno = self.fromlineno
        self.tolineno = lastchild.tolineno
        self.blockstart_tolineno = self.args.tolineno

    def block_range(self, lineno):
        """return block line numbers.

        start from the "def" position whatever the given lineno
        """
        return self.fromlineno, self.tolineno

    def getattr(self, name, context=None):
        """this method doesn't look in the instance_attrs dictionary since it's
        done by an Instance proxy at inference time.
        """
        if name == '__module__':
            return [cf(self.root().qname())]
        if name in self.instance_attrs:
            return self.instance_attrs[name]
        return std_special_attributes(self, name, False)

    def is_method(self):
        """return true if the function node should be considered as a method"""
        # check we are defined in a Class, because this is usually expected
        # (e.g. pylint...) when is_method() return True
        return self.type != 'function' and isinstance(self.parent.frame(), Class)

    def decoratornames(self):
        """return a list of decorator qualified names"""
        result = set()
        decoratornodes = []
        if self.decorators is not None:
            decoratornodes += self.decorators.nodes
        decoratornodes += self.extra_decorators
        for decnode in decoratornodes:
            for infnode in decnode.infer():
                result.add(infnode.qname())
        return result
    decoratornames = cached(decoratornames)

    def is_bound(self):
        """return true if the function is bound to an Instance or a class"""
        return self.type == 'classmethod'

    def is_abstract(self, pass_is_abstract=True):
        """Returns True if the method is abstract.

        A method is considered abstract if
         - the only statement is 'raise NotImplementedError', or
         - the only statement is 'pass' and pass_is_abstract is True, or
         - the method is annotated with abc.astractproperty/abc.abstractmethod
        """
        if self.decorators:
            for node in self.decorators.nodes:
                try:
                    infered = node.infer().next()
                except InferenceError:
                    continue
                if infered and infered.qname() in ('abc.abstractproperty',
                                                   'abc.abstractmethod'):
                    return True

        for child_node in self.body:
            if isinstance(child_node, Raise):
                if child_node.raises_not_implemented():
                    return True
            if pass_is_abstract and isinstance(child_node, Pass):
                return True
            return False
        # empty function is the same as function with a single "pass" statement
        if pass_is_abstract:
            return True

    def is_generator(self):
        """return true if this is a generator function"""
        # XXX should be flagged, not computed
        try:
            return self.nodes_of_class((Yield, YieldFrom),
                                       skip_klass=(Function, Lambda)).next()
        except StopIteration:
            return False

    def infer_call_result(self, caller, context=None):
        """infer what a function is returning when called"""
        if self.is_generator():
            yield Generator()
            return
        returns = self.nodes_of_class(Return, skip_klass=Function)
        for returnnode in returns:
            if returnnode.value is None:
                yield Const(None)
            else:
                try:
                    for infered in returnnode.value.infer(context):
                        yield infered
                except InferenceError:
                    yield YES


def _rec_get_names(args, names=None):
    """return a list of all argument names"""
    if names is None:
        names = []
    for arg in args:
        if isinstance(arg, Tuple):
            _rec_get_names(arg.elts, names)
        else:
            names.append(arg.name)
    return names


# Class ######################################################################


def _is_metaclass(klass):
    """ Return if the given class can be
    used as a metaclass.
    """
    if klass.name == 'type':
        return True
    for base in klass.bases:
        try:
            for baseobj in base.infer():
                if isinstance(baseobj, Instance):
                    # not abstract
                    return False
                if baseobj is YES:
                    continue
                if baseobj is klass:
                    continue
                if not isinstance(baseobj, Class):
                    continue
                if baseobj._type == 'metaclass':
                    return True
                if _is_metaclass(baseobj):
                    return True
        except InferenceError:
            continue
    return False


def _class_type(klass, ancestors=None):
    """return a Class node type to differ metaclass, interface and exception
    from 'regular' classes
    """
    # XXX we have to store ancestors in case we have a ancestor loop
    if klass._type is not None:
        return klass._type
    if _is_metaclass(klass):
        klass._type = 'metaclass'
    elif klass.name.endswith('Interface'):
        klass._type = 'interface'
    elif klass.name.endswith('Exception'):
        klass._type = 'exception'
    else:
        if ancestors is None:
            ancestors = set()
        if klass in ancestors:
            # XXX we are in loop ancestors, and have found no type
            klass._type = 'class'
            return 'class'
        ancestors.add(klass)
        # print >> sys.stderr, '_class_type', repr(klass)
        for base in klass.ancestors(recurs=False):
            name = _class_type(base, ancestors)
            if name != 'class':
                if name == 'metaclass' and not _is_metaclass(klass):
                    # don't propagate it if the current class
                    # can't be a metaclass
                    continue
                klass._type = base.type
                break
    if klass._type is None:
        klass._type = 'class'
    return klass._type

def _iface_hdlr(iface_node):
    """a handler function used by interfaces to handle suspicious
    interface nodes
    """
    return True


class Class(Statement, LocalsDictNodeNG, FilterStmtsMixin):

    # some of the attributes below are set by the builder module or
    # by a raw factories

    # a dictionary of class instances attributes
    _astroid_fields = ('decorators', 'bases', 'body') # name

    decorators = None
    special_attributes = set(('__name__', '__doc__', '__dict__', '__module__',
                              '__bases__', '__mro__', '__subclasses__'))
    blockstart_tolineno = None

    _type = None
    type = property(_class_type,
                    doc="class'type, possible values are 'class' | "
                    "'metaclass' | 'interface' | 'exception'")

    def __init__(self, name, doc):
        self.instance_attrs = {}
        self.locals = {}
        self.bases = []
        self.body = []
        self.name = name
        self.doc = doc

    def _newstyle_impl(self, context=None):
        if context is None:
            context = InferenceContext()
        if self._newstyle is not None:
            return self._newstyle
        for base in self.ancestors(recurs=False, context=context):
            if base._newstyle_impl(context):
                self._newstyle = True
                break
        klass = self._explicit_metaclass()
        # could be any callable, we'd need to infer the result of klass(name,
        # bases, dict).  punt if it's not a class node.
        if klass is not None and isinstance(klass, Class):
            self._newstyle = klass._newstyle_impl(context)
        if self._newstyle is None:
            self._newstyle = False
        return self._newstyle

    _newstyle = None
    newstyle = property(_newstyle_impl,
                        doc="boolean indicating if it's a new style class"
                        "or not")

    def set_line_info(self, lastchild):
        self.fromlineno = self.lineno
        self.blockstart_tolineno = self.bases and self.bases[-1].tolineno or self.fromlineno
        if lastchild is not None:
            self.tolineno = lastchild.tolineno
        # else this is a class with only a docstring, then tolineno is (should be) already ok

    def block_range(self, lineno):
        """return block line numbers.

        start from the "class" position whatever the given lineno
        """
        return self.fromlineno, self.tolineno

    def pytype(self):
        if self.newstyle:
            return '%s.type' % BUILTINS
        return '%s.classobj' % BUILTINS

    def display_type(self):
        return 'Class'

    def callable(self):
        return True

    def _is_subtype_of(self, type_name):
        if self.qname() == type_name:
            return True
        for anc in self.ancestors():
            if anc.qname() == type_name:
                return True

    def infer_call_result(self, caller, context=None):
        """infer what a class is returning when called"""
        if self._is_subtype_of('%s.type' % (BUILTINS,)) and len(caller.args) == 3:
            name_node = caller.args[0].infer().next()
            if isinstance(name_node, Const) and isinstance(name_node.value, basestring):
                name = name_node.value
            else:
                yield YES
                return
            result = Class(name, None)
            bases = caller.args[1].infer().next()
            if isinstance(bases, (Tuple, List)):
                result.bases = bases.itered()
            else:
                # There is currently no AST node that can represent an 'unknown'
                # node (YES is not an AST node), therefore we simply return YES here
                # although we know at least the name of the class.
                yield YES
                return
            result.parent = caller.parent
            yield result
        else:
            yield Instance(self)

    def scope_lookup(self, node, name, offset=0):
        if node in self.bases:
            frame = self.parent.frame()
            # line offset to avoid that class A(A) resolve the ancestor to
            # the defined class
            offset = -1
        else:
            frame = self
        return frame._scope_lookup(node, name, offset)

    # list of parent class as a list of string (i.e. names as they appear
    # in the class definition) XXX bw compat
    def basenames(self):
        return [bnode.as_string() for bnode in self.bases]
    basenames = property(basenames)

    def ancestors(self, recurs=True, context=None):
        """return an iterator on the node base classes in a prefixed
        depth first order

        :param recurs:
          boolean indicating if it should recurse or return direct
          ancestors only
        """
        # FIXME: should be possible to choose the resolution order
        # XXX inference make infinite loops possible here (see BaseTransformer
        # manipulation in the builder module for instance)
        yielded = set([self])
        if context is None:
            context = InferenceContext()
        for stmt in self.bases:
            with context.restore_path():
                try:
                    for baseobj in stmt.infer(context):
                        if not isinstance(baseobj, Class):
                            if isinstance(baseobj, Instance):
                                baseobj = baseobj._proxied
                            else:
                                # duh ?
                                continue
                        if baseobj in yielded:
                            continue # cf xxx above
                        yielded.add(baseobj)
                        yield baseobj
                        if recurs:
                            for grandpa in baseobj.ancestors(True, context):
                                if grandpa in yielded:
                                    continue # cf xxx above
                                yielded.add(grandpa)
                                yield grandpa
                except InferenceError:
                    # XXX log error ?
                    continue

    def local_attr_ancestors(self, name, context=None):
        """return an iterator on astroid representation of parent classes
        which have <name> defined in their locals
        """
        for astroid in self.ancestors(context=context):
            if name in astroid:
                yield astroid

    def instance_attr_ancestors(self, name, context=None):
        """return an iterator on astroid representation of parent classes
        which have <name> defined in their instance attribute dictionary
        """
        for astroid in self.ancestors(context=context):
            if name in astroid.instance_attrs:
                yield astroid

    def has_base(self, node):
        return node in self.bases

    def local_attr(self, name, context=None):
        """return the list of assign node associated to name in this class
        locals or in its parents

        :raises `NotFoundError`:
          if no attribute with this name has been find in this class or
          its parent classes
        """
        try:
            return self.locals[name]
        except KeyError:
            # get if from the first parent implementing it if any
            for class_node in self.local_attr_ancestors(name, context):
                return class_node.locals[name]
        raise NotFoundError(name)
    local_attr = remove_nodes(local_attr, DelAttr)

    def instance_attr(self, name, context=None):
        """return the astroid nodes associated to name in this class instance
        attributes dictionary and in its parents

        :raises `NotFoundError`:
          if no attribute with this name has been find in this class or
          its parent classes
        """
        # Return a copy, so we don't modify self.instance_attrs,
        # which could lead to infinite loop.
        values = list(self.instance_attrs.get(name, []))
        # get all values from parents
        for class_node in self.instance_attr_ancestors(name, context):
            values += class_node.instance_attrs[name]
        if not values:
            raise NotFoundError(name)
        return values
    instance_attr = remove_nodes(instance_attr, DelAttr)

    def instanciate_class(self):
        """return Instance of Class node, else return self"""
        return Instance(self)

    def getattr(self, name, context=None):
        """this method doesn't look in the instance_attrs dictionary since it's
        done by an Instance proxy at inference time.

        It may return a YES object if the attribute has not been actually
        found but a __getattr__ or __getattribute__ method is defined
        """
        values = self.locals.get(name, [])
        if name in self.special_attributes:
            if name == '__module__':
                return [cf(self.root().qname())] + values
            # FIXME: do we really need the actual list of ancestors?
            # returning [Tuple()] + values don't break any test
            # this is ticket http://www.logilab.org/ticket/52785
            # XXX need proper meta class handling + MRO implementation
            if name == '__bases__' or (name == '__mro__' and self.newstyle):
                node = Tuple()
                node.items = self.ancestors(recurs=True, context=context)
                return [node] + values
            return std_special_attributes(self, name)
        # don't modify the list in self.locals!
        values = list(values)
        for classnode in self.ancestors(recurs=True, context=context):
            values += classnode.locals.get(name, [])
        if not values:
            raise NotFoundError(name)
        return values

    def igetattr(self, name, context=None):
        """inferred getattr, need special treatment in class to handle
        descriptors
        """
        # set lookup name since this is necessary to infer on import nodes for
        # instance
        context = copy_context(context)
        context.lookupname = name
        try:
            for infered in _infer_stmts(self.getattr(name, context), context,
                                        frame=self):
                # yield YES object instead of descriptors when necessary
                if not isinstance(infered, Const) and isinstance(infered, Instance):
                    try:
                        infered._proxied.getattr('__get__', context)
                    except NotFoundError:
                        yield infered
                    else:
                        yield YES
                else:
                    yield function_to_method(infered, self)
        except NotFoundError:
            if not name.startswith('__') and self.has_dynamic_getattr(context):
                # class handle some dynamic attributes, return a YES object
                yield YES
            else:
                raise InferenceError(name)

    def has_dynamic_getattr(self, context=None):
        """return True if the class has a custom __getattr__ or
        __getattribute__ method
        """
        # need to explicitly handle optparse.Values (setattr is not detected)
        if self.name == 'Values' and self.root().name == 'optparse':
            return True
        try:
            self.getattr('__getattr__', context)
            return True
        except NotFoundError:
            #if self.newstyle: XXX cause an infinite recursion error
            try:
                getattribute = self.getattr('__getattribute__', context)[0]
                if getattribute.root().name != BUILTINS:
                    # class has a custom __getattribute__ defined
                    return True
            except NotFoundError:
                pass
        return False

    def methods(self):
        """return an iterator on all methods defined in the class and
        its ancestors
        """
        done = {}
        for astroid in chain(iter((self,)), self.ancestors()):
            for meth in astroid.mymethods():
                if meth.name in done:
                    continue
                done[meth.name] = None
                yield meth

    def mymethods(self):
        """return an iterator on all methods defined in the class"""
        for member in self.values():
            if isinstance(member, Function):
                yield member

    def interfaces(self, herited=True, handler_func=_iface_hdlr):
        """return an iterator on interfaces implemented by the given
        class node
        """
        # FIXME: what if __implements__ = (MyIFace, MyParent.__implements__)...
        try:
            implements = Instance(self).getattr('__implements__')[0]
        except NotFoundError:
            return
        if not herited and not implements.frame() is self:
            return
        found = set()
        missing = False
        for iface in unpack_infer(implements):
            if iface is YES:
                missing = True
                continue
            if not iface in found and handler_func(iface):
                found.add(iface)
                yield iface
        if missing:
            raise InferenceError()

    _metaclass = None
    def _explicit_metaclass(self):
        """ Return the explicit defined metaclass
        for the current class.

        An explicit defined metaclass is defined
        either by passing the ``metaclass`` keyword argument
        in the class definition line (Python 3) or (Python 2) by
        having a ``__metaclass__`` class attribute, or if there are
        no explicit bases but there is a global ``__metaclass__`` variable.
        """
        if self._metaclass:
            # Expects this from Py3k TreeRebuilder
            try:
                return next(node for node in self._metaclass.infer()
                            if node is not YES)
            except (InferenceError, StopIteration):
                return None
        if sys.version_info >= (3, ):
            return None

        if '__metaclass__' in self.locals:
            assignment = self.locals['__metaclass__'][-1]
        elif self.bases:
            return None
        elif '__metaclass__' in self.root().locals:
            assignments = [ass for ass in self.root().locals['__metaclass__']
                           if ass.lineno < self.lineno]
            if not assignments:
                return None
            assignment = assignments[-1]
        else:
            return None

        try:
            infered = assignment.infer().next()
        except InferenceError:
            return
        if infered is YES: # don't expose this
            return None
        return infered

    def metaclass(self):
        """ Return the metaclass of this class.

        If this class does not define explicitly a metaclass,
        then the first defined metaclass in ancestors will be used
        instead.
        """
        klass = self._explicit_metaclass()
        if klass is None:
            for parent in self.ancestors():
                klass = parent.metaclass()
                if klass is not None:
                    break
        return klass

    def _islots(self):
        """ Return an iterator with the inferred slots. """
        if '__slots__' not in self.locals:
            return
        for slots in self.igetattr('__slots__'):
            # check if __slots__ is a valid type
            for meth in ITER_METHODS:
                try:
                    slots.getattr(meth)
                    break
                except NotFoundError:
                    continue
            else:
                continue

            if isinstance(slots, Const):
                # a string. Ignore the following checks,
                # but yield the node, only if it has a value
                if slots.value:
                    yield slots
                continue
            if not hasattr(slots, 'itered'):
                # we can't obtain the values, maybe a .deque?
                continue

            if isinstance(slots, Dict):
                values = [item[0] for item in slots.items]
            else:
                values = slots.itered()
            if values is YES:
                continue

            for elt in values:
                try:
                    for infered in elt.infer():
                        if infered is YES:
                            continue
                        if (not isinstance(infered, Const) or
                                not isinstance(infered.value, str)):
                            continue
                        if not infered.value:
                            continue
                        yield infered
                except InferenceError:
                    continue

    # Cached, because inferring them all the time is expensive
    @cached
    def slots(self):
        """ Return all the slots for this node. """
        return list(self._islots())