/rpython/annotator/unaryop.py

"""
Unary operations on SomeValues.
"""
from __future__ import absolute_import

from collections import defaultdict

from rpython.tool.pairtype import pair
from rpython.flowspace.operation import op
from rpython.flowspace.model import const, Constant
from rpython.flowspace.argument import CallSpec
from rpython.annotator.model import (SomeObject, SomeInteger, SomeBool,
    SomeString, SomeChar, SomeList, SomeDict, SomeTuple, SomeImpossibleValue,
    SomeUnicodeCodePoint, SomeInstance, SomeBuiltin, SomeBuiltinMethod,
    SomeFloat, SomeIterator, SomePBC, SomeNone, SomeTypeOf, s_ImpossibleValue,
    s_Bool, s_None, s_Int, unionof, add_knowntypedata,
    SomeWeakRef, SomeUnicodeString, SomeByteArray)
from rpython.annotator.bookkeeper import getbookkeeper, immutablevalue
from rpython.annotator.binaryop import _clone ## XXX where to put this?
from rpython.annotator.binaryop import _dict_can_only_throw_keyerror
from rpython.annotator.binaryop import _dict_can_only_throw_nothing
from rpython.annotator.classdesc import ClassDesc, is_primitive_type, BuiltinTypeDesc
from rpython.annotator.model import AnnotatorError
from rpython.annotator.argument import simple_args, complex_args

UNARY_OPERATIONS = set([oper.opname for oper in op.__dict__.values()
                        if oper.dispatch == 1])
UNARY_OPERATIONS.remove('contains')


@op.type.register(SomeObject)
def type_SomeObject(annotator, v_arg):
    return SomeTypeOf([v_arg])


def our_issubclass(bk, cls1, cls2):
    def toclassdesc(cls):
        if isinstance(cls, ClassDesc):
            return cls
        elif is_primitive_type(cls):
            return BuiltinTypeDesc(cls)
        else:
            return bk.getdesc(cls)
    return toclassdesc(cls1).issubclass(toclassdesc(cls2))


def s_isinstance(annotator, s_obj, s_type, variables):
    if not s_type.is_constant():
        return SomeBool()
    r = SomeBool()
    typ = s_type.const
    bk = annotator.bookkeeper
    if s_obj.is_constant():
        r.const = isinstance(s_obj.const, typ)
    elif our_issubclass(bk, s_obj.knowntype, typ):
        if not s_obj.can_be_none():
            r.const = True
    elif not our_issubclass(bk, typ, s_obj.knowntype):
        r.const = False
    elif s_obj.knowntype == int and typ == bool: # xxx this will explode in case of generalisation
                                            # from bool to int, notice that isinstance( , bool|int)
                                            # is quite border case for RPython
        r.const = False
    for v in variables:
        assert v.annotation == s_obj
    knowntypedata = defaultdict(dict)
    if not hasattr(typ, '_freeze_') and isinstance(s_type, SomePBC):
        add_knowntypedata(knowntypedata, True, variables, bk.valueoftype(typ))
    r.set_knowntypedata(knowntypedata)
    return r

@op.isinstance.register(SomeObject)
def isinstance_SomeObject(annotator, v_obj, v_cls):
    s_obj = annotator.annotation(v_obj)
    s_cls = annotator.annotation(v_cls)
    return s_isinstance(annotator, s_obj, s_cls, variables=[v_obj])


@op.bool.register(SomeObject)
def bool_SomeObject(annotator, obj):
    r = SomeBool()
    annotator.annotation(obj).bool_behavior(r)
    s_nonnone_obj = annotator.annotation(obj)
    if s_nonnone_obj.can_be_none():
        s_nonnone_obj = s_nonnone_obj.nonnoneify()
    knowntypedata = defaultdict(dict)
    add_knowntypedata(knowntypedata, True, [obj], s_nonnone_obj)
    r.set_knowntypedata(knowntypedata)
    return r

@op.contains.register(SomeObject)
def contains_SomeObject(annotator, obj, element):
    return s_Bool
contains_SomeObject.can_only_throw = []

@op.contains.register(SomeNone)
def contains_SomeNone(annotator, obj, element):
    # return False here for the case "... in None", because it can be later
    # generalized to "... in d" where d is either None or the empty dict
    # (which would also return the constant False)
    s_bool = SomeBool()
    s_bool.const = False
    return s_bool
contains_SomeNone.can_only_throw = []


@op.contains.register(SomeInteger)
@op.contains.register(SomeFloat)
@op.contains.register(SomeBool)
def contains_number(annotator, number, element):
    raise AnnotatorError("number is not iterable")


@op.simple_call.register(SomeObject)
def simple_call_SomeObject(annotator, func, *args):
    s_func = annotator.annotation(func)
    argspec = simple_args([annotator.annotation(arg) for arg in args])
    return s_func.call(argspec)

@op.call_args.register_transform(SomeObject)
def transform_varargs(annotator, v_func, v_shape, *data_v):
    callspec = CallSpec.fromshape(v_shape.value, list(data_v))
    v_vararg = callspec.w_stararg
    if callspec.w_stararg:
        s_vararg = annotator.annotation(callspec.w_stararg)
        if not isinstance(s_vararg, SomeTuple):
            raise AnnotatorError(
                "Calls like f(..., *arg) require 'arg' to be a tuple")
        n_items = len(s_vararg.items)
        ops = [op.getitem(v_vararg, const(i)) for i in range(n_items)]
        new_args = callspec.arguments_w + [hlop.result for hlop in ops]
        if callspec.keywords:
            newspec = CallSpec(new_args, callspec.keywords)
            shape, data_v = newspec.flatten()
            call_op = op.call_args(v_func, const(shape), *data_v)
        else:
            call_op = op.simple_call(v_func, *new_args)
        ops.append(call_op)
        return ops


@op.call_args.register(SomeObject)
def call_args(annotator, func, *args_v):
    callspec = complex_args([annotator.annotation(v_arg) for v_arg in args_v])
    return annotator.annotation(func).call(callspec)

@op.issubtype.register(SomeObject)
def issubtype(annotator, v_type, v_cls):
    s_type = v_type.annotation
    s_cls = annotator.annotation(v_cls)
    if s_type.is_constant() and s_cls.is_constant():
        return annotator.bookkeeper.immutablevalue(
            issubclass(s_type.const, s_cls.const))
    return s_Bool

class __extend__(SomeObject):

    def len(self):
        return SomeInteger(nonneg=True)

    def bool_behavior(self, s):
        if self.is_immutable_constant():
            s.const = bool(self.const)
        else:
            s_len = self.len()
            if s_len.is_immutable_constant():
                s.const = s_len.const > 0

    def hash(self):
        raise AnnotatorError("cannot use hash() in RPython")

    def str(self):
        return SomeString()

    def unicode(self):
        return SomeUnicodeString()

    def repr(self):
        return SomeString()

    def hex(self):
        return SomeString()

    def oct(self):
        return SomeString()

    def id(self):
        raise Exception("cannot use id() in RPython; "
                        "see objectmodel.compute_xxx()")

    def int(self):
        return SomeInteger()

    def float(self):
        return SomeFloat()

    def delattr(self, s_attr):
        if self.__class__ != SomeObject or self.knowntype != object:
            getbookkeeper().warning(
                ("delattr on potentally non-SomeObjects is not RPythonic: delattr(%r,%r)" %
                 (self, s_attr)))

    def find_method(self, name):
        "Look for a special-case implementation for the named method."
        try:
            analyser = getattr(self.__class__, 'method_' + name)
        except AttributeError:
            return None
        else:
            return SomeBuiltinMethod(analyser, self, name)

    def getattr(self, s_attr):
        # get a SomeBuiltin if the SomeObject has
        # a corresponding method to handle it
        if not s_attr.is_constant() or not isinstance(s_attr.const, str):
            raise AnnotatorError("getattr(%r, %r) has non-constant argument"
                                 % (self, s_attr))
        attr = s_attr.const
        s_method = self.find_method(attr)
        if s_method is not None:
            return s_method
        # if the SomeObject is itself a constant, allow reading its attrs
        if self.is_immutable_constant() and hasattr(self.const, attr):
            return immutablevalue(getattr(self.const, attr))
        raise AnnotatorError("Cannot find attribute %r on %r" % (attr, self))
    getattr.can_only_throw = []

    def setattr(self, *args):
        return s_ImpossibleValue

    def bind_callables_under(self, classdef, name):
        return self   # default unbound __get__ implementation

    def call(self, args, implicit_init=False):
        raise AnnotatorError("Cannot prove that the object is callable")

    def hint(self, *args_s):
        return self

    def getslice(self, *args):
        return s_ImpossibleValue

    def setslice(self, *args):
        return s_ImpossibleValue

    def delslice(self, *args):
        return s_ImpossibleValue

    def pos(self):
        return s_ImpossibleValue
    neg = abs = ord = invert = long = iter = next = pos


class __extend__(SomeFloat):

    def pos(self):
        return self

    def neg(self):
        return SomeFloat()

    abs = neg

    def bool(self):
        if self.is_immutable_constant():
            return getbookkeeper().immutablevalue(bool(self.const))
        return s_Bool

    def len(self):
        raise AnnotatorError("'float' has no length")

class __extend__(SomeInteger):

    def invert(self):
        return SomeInteger(knowntype=self.knowntype)
    invert.can_only_throw = []

    def pos(self):
        return SomeInteger(knowntype=self.knowntype)

    pos.can_only_throw = []
    int = pos

    # these are the only ones which can overflow:

    def neg(self):
        return SomeInteger(knowntype=self.knowntype)

    neg.can_only_throw = []
    neg_ovf = _clone(neg, [OverflowError])

    def abs(self):
        return SomeInteger(nonneg=True, knowntype=self.knowntype)

    abs.can_only_throw = []
    abs_ovf = _clone(abs, [OverflowError])

    def len(self):
        raise AnnotatorError("'int' has no length")


class __extend__(SomeBool):
    def bool(self):
        return self

    def invert(self):
        return SomeInteger()

    invert.can_only_throw = []

    def neg(self):
        return SomeInteger()

    neg.can_only_throw = []
    neg_ovf = _clone(neg, [OverflowError])

    def abs(self):
        return SomeInteger(nonneg=True)

    abs.can_only_throw = []
    abs_ovf = _clone(abs, [OverflowError])

    def pos(self):
        return SomeInteger(nonneg=True)

    pos.can_only_throw = []
    int = pos

class __extend__(SomeTuple):

    def len(self):
        return immutablevalue(len(self.items))

    def iter(self):
        return SomeIterator(self)
    iter.can_only_throw = []

    def getanyitem(self, position):
        return unionof(*self.items)

    def getslice(self, s_start, s_stop):
        assert s_start.is_immutable_constant(),"tuple slicing: needs constants"
        assert s_stop.is_immutable_constant(), "tuple slicing: needs constants"
        items = self.items[s_start.const:s_stop.const]
        return SomeTuple(items)

@op.contains.register(SomeList)
def contains_SomeList(annotator, obj, element):
    annotator.annotation(obj).listdef.generalize(annotator.annotation(element))
    return s_Bool
contains_SomeList.can_only_throw = []


class __extend__(SomeList):

    def method_append(self, s_value):
        self.listdef.resize()
        self.listdef.generalize(s_value)

    def method_extend(self, s_iterable):
        self.listdef.resize()
        if isinstance(s_iterable, SomeList):   # unify the two lists
            self.listdef.agree(getbookkeeper(), s_iterable.listdef)
        else:
            s_iter = s_iterable.iter()
            self.method_append(s_iter.next())

    def method_reverse(self):
        self.listdef.mutate()

    def method_insert(self, s_index, s_value):
        self.method_append(s_value)

    def method_remove(self, s_value):
        self.listdef.resize()
        self.listdef.generalize(s_value)

    def method_pop(self, s_index=None):
        position = getbookkeeper().position_key
        self.listdef.resize()
        return self.listdef.read_item(position)
    method_pop.can_only_throw = [IndexError]

    def method_index(self, s_value):
        self.listdef.generalize(s_value)
        return SomeInteger(nonneg=True)

    def len(self):
        position = getbookkeeper().position_key
        s_item = self.listdef.read_item(position)
        if isinstance(s_item, SomeImpossibleValue):
            return immutablevalue(0)
        return SomeObject.len(self)

    def iter(self):
        return SomeIterator(self)
    iter.can_only_throw = []

    def getanyitem(self, position):
        return self.listdef.read_item(position)

    def hint(self, *args_s):
        hints = args_s[-1].const
        if 'maxlength' in hints:
            # only for iteration over lists or dicts or strs at the moment,
            # not over an iterator object (because it has no known length)
            s_iterable = args_s[0]
            if isinstance(s_iterable, (SomeList, SomeDict, SomeString)):
                self = SomeList(self.listdef) # create a fresh copy
                self.listdef.resize()
                self.listdef.listitem.hint_maxlength = True
        elif 'fence' in hints:
            self = self.listdef.offspring(getbookkeeper())
        return self

    def getslice(self, s_start, s_stop):
        bk = getbookkeeper()
        check_negative_slice(s_start, s_stop)
        return self.listdef.offspring(bk)

    def setslice(self, s_start, s_stop, s_iterable):
        check_negative_slice(s_start, s_stop)
        if not isinstance(s_iterable, SomeList):
            raise Exception("list[start:stop] = x: x must be a list")
        self.listdef.mutate()
        self.listdef.agree(getbookkeeper(), s_iterable.listdef)
        self.listdef.resize()

    def delslice(self, s_start, s_stop):
        check_negative_slice(s_start, s_stop)
        self.listdef.resize()

def check_negative_slice(s_start, s_stop, error="slicing"):
    if isinstance(s_start, SomeInteger) and not s_start.nonneg:
        raise AnnotatorError("%s: not proven to have non-negative start" %
                             error)
    if isinstance(s_stop, SomeInteger) and not s_stop.nonneg and \
           getattr(s_stop, 'const', 0) != -1:
        raise AnnotatorError("%s: not proven to have non-negative stop" % error)


def dict_contains(s_dct, s_element, position):
    s_dct.dictdef.generalize_key(s_element)
    if s_dct._is_empty(position):
        s_bool = SomeBool()
        s_bool.const = False
        return s_bool
    return s_Bool

@op.contains.register(SomeDict)
def contains_SomeDict(annotator, dct, element):
    position = annotator.bookkeeper.position_key
    return dict_contains(annotator.annotation(dct),
                         annotator.annotation(element),
                         position)
contains_SomeDict.can_only_throw = _dict_can_only_throw_nothing

class __extend__(SomeDict):

    def _is_empty(self, position):
        s_key = self.dictdef.read_key(position)
        s_value = self.dictdef.read_value(position)
        return (isinstance(s_key, SomeImpossibleValue) or
                isinstance(s_value, SomeImpossibleValue))

    def len(self):
        position = getbookkeeper().position_key
        if self._is_empty(position):
            return immutablevalue(0)
        return SomeObject.len(self)

    def iter(self):
        return SomeIterator(self)
    iter.can_only_throw = []

    def getanyitem(self, position, variant='keys'):
        if variant == 'keys':
            return self.dictdef.read_key(position)
        elif variant == 'values':
            return self.dictdef.read_value(position)
        elif variant == 'items' or variant == 'items_with_hash':
            s_key   = self.dictdef.read_key(position)
            s_value = self.dictdef.read_value(position)
            if (isinstance(s_key, SomeImpossibleValue) or
                isinstance(s_value, SomeImpossibleValue)):
                return s_ImpossibleValue
            elif variant == 'items':
                return SomeTuple((s_key, s_value))
            elif variant == 'items_with_hash':
                return SomeTuple((s_key, s_value, s_Int))
        elif variant == 'keys_with_hash':
            s_key = self.dictdef.read_key(position)
            if isinstance(s_key, SomeImpossibleValue):
                return s_ImpossibleValue
            return SomeTuple((s_key, s_Int))
        raise ValueError(variant)

    def method_get(self, key, dfl):
        position = getbookkeeper().position_key
        self.dictdef.generalize_key(key)
        self.dictdef.generalize_value(dfl)
        return self.dictdef.read_value(position)

    method_setdefault = method_get

    def method_copy(self):
        return SomeDict(self.dictdef)

    def method_update(dct1, dct2):
        if s_None.contains(dct2):
            return SomeImpossibleValue()
        dct1.dictdef.union(dct2.dictdef)

    def method__prepare_dict_update(dct, num):
        pass

    def method_keys(self):
        bk = getbookkeeper()
        return bk.newlist(self.dictdef.read_key(bk.position_key))

    def method_values(self):
        bk = getbookkeeper()
        return bk.newlist(self.dictdef.read_value(bk.position_key))

    def method_items(self):
        bk = getbookkeeper()
        return bk.newlist(self.getanyitem(bk.position_key, variant='items'))

    def method_iterkeys(self):
        return SomeIterator(self, 'keys')

    def method_itervalues(self):
        return SomeIterator(self, 'values')

    def method_iteritems(self):
        return SomeIterator(self, 'items')

    def method_iterkeys_with_hash(self):
        return SomeIterator(self, 'keys_with_hash')

    def method_iteritems_with_hash(self):
        return SomeIterator(self, 'items_with_hash')

    def method_clear(self):
        pass

    def method_popitem(self):
        position = getbookkeeper().position_key
        return self.getanyitem(position, variant='items')

    def method_pop(self, s_key, s_dfl=None):
        self.dictdef.generalize_key(s_key)
        if s_dfl is not None:
            self.dictdef.generalize_value(s_dfl)
        position = getbookkeeper().position_key
        return self.dictdef.read_value(position)

    def method_contains_with_hash(self, s_key, s_hash):
        position = getbookkeeper().position_key
        return dict_contains(self, s_key, position)
    method_contains_with_hash.can_only_throw = _dict_can_only_throw_nothing

    def method_setitem_with_hash(self, s_key, s_hash, s_value):
        pair(self, s_key).setitem(s_value)
    method_setitem_with_hash.can_only_throw = _dict_can_only_throw_nothing

    def method_getitem_with_hash(self, s_key, s_hash):
        # XXX: copy of binaryop.getitem_SomeDict
        self.dictdef.generalize_key(s_key)
        position = getbookkeeper().position_key
        return self.dictdef.read_value(position)
    method_getitem_with_hash.can_only_throw = _dict_can_only_throw_keyerror

    def method_delitem_with_hash(self, s_key, s_hash):
        pair(self, s_key).delitem()
    method_delitem_with_hash.can_only_throw = _dict_can_only_throw_keyerror

@op.contains.register(SomeString)
@op.contains.register(SomeUnicodeString)
def contains_String(annotator, string, char):
    if annotator.annotation(char).is_constant() and annotator.annotation(char).const == "\0":
        r = SomeBool()
        knowntypedata = defaultdict(dict)
        add_knowntypedata(knowntypedata, False, [string],
                          annotator.annotation(string).nonnulify())
        r.set_knowntypedata(knowntypedata)
        return r
    else:
        return contains_SomeObject(annotator, string, char)
contains_String.can_only_throw = []


class __extend__(SomeString,
                 SomeUnicodeString):

    def method_startswith(self, frag):
        if self.is_constant() and frag.is_constant():
            return immutablevalue(self.const.startswith(frag.const))
        return s_Bool

    def method_endswith(self, frag):
        if self.is_constant() and frag.is_constant():
            return immutablevalue(self.const.endswith(frag.const))
        return s_Bool

    def method_find(self, frag, start=None, end=None):
        check_negative_slice(start, end, "find")
        return SomeInteger()

    def method_rfind(self, frag, start=None, end=None):
        check_negative_slice(start, end, "rfind")
        return SomeInteger()

    def method_count(self, frag, start=None, end=None):
        check_negative_slice(start, end, "count")
        return SomeInteger(nonneg=True)

    def method_strip(self, chr=None):
        if chr is None and isinstance(self, SomeUnicodeString):
            raise AnnotatorError("unicode.strip() with no arg is not RPython")
        return self.basestringclass(no_nul=self.no_nul)

    def method_lstrip(self, chr=None):
        if chr is None and isinstance(self, SomeUnicodeString):
            raise AnnotatorError("unicode.lstrip() with no arg is not RPython")
        return self.basestringclass(no_nul=self.no_nul)

    def method_rstrip(self, chr=None):
        if chr is None and isinstance(self, SomeUnicodeString):
            raise AnnotatorError("unicode.rstrip() with no arg is not RPython")
        return self.basestringclass(no_nul=self.no_nul)

    def method_join(self, s_list):
        if s_None.contains(s_list):
            return SomeImpossibleValue()
        position = getbookkeeper().position_key
        s_item = s_list.listdef.read_item(position)
        if s_None.contains(s_item):
            if isinstance(self, SomeUnicodeString):
                return immutablevalue(u"")
            return immutablevalue("")
        no_nul = self.no_nul and s_item.no_nul
        return self.basestringclass(no_nul=no_nul)

    def iter(self):
        return SomeIterator(self)
    iter.can_only_throw = []

    def getanyitem(self, position):
        return self.basecharclass()

    def method_split(self, patt, max=-1):
        # special-case for .split( '\x00') or .split(u'\x00')
        if max == -1 and patt.is_constant() and (
               len(patt.const) == 1 and ord(patt.const) == 0):
            no_nul = True
        else:
            no_nul = self.no_nul
        s_item = self.basestringclass(no_nul=no_nul)
        return getbookkeeper().newlist(s_item)

    def method_rsplit(self, patt, max=-1):
        s_item = self.basestringclass(no_nul=self.no_nul)
        return getbookkeeper().newlist(s_item)

    def method_replace(self, s1, s2):
        return self.basestringclass(no_nul=self.no_nul and s2.no_nul)

    def getslice(self, s_start, s_stop):
        check_negative_slice(s_start, s_stop)
        result = self.basestringclass(no_nul=self.no_nul)
        return result

    def method_format(self, *args):
        raise AnnotatorError("Method format() is not RPython")


class __extend__(SomeByteArray):
    def getslice(ba, s_start, s_stop):
        check_negative_slice(s_start, s_stop)
        return SomeByteArray()

class __extend__(SomeUnicodeString):
    def method_encode(self, s_enc):
        if not s_enc.is_constant():
            raise AnnotatorError("Non-constant encoding not supported")
        enc = s_enc.const
        if enc not in ('ascii', 'latin-1', 'utf-8'):
            raise AnnotatorError("Encoding %s not supported for unicode" % (enc,))
        return SomeString(no_nul=self.no_nul)
    method_encode.can_only_throw = [UnicodeEncodeError]


class __extend__(SomeString):
    def method_isdigit(self):
        return s_Bool

    def method_isalpha(self):
        return s_Bool

    def method_isalnum(self):
        return s_Bool

    def method_upper(self):
        return SomeString()

    def method_lower(self):
        return SomeString()

    def method_splitlines(self, s_keep_newlines=None):
        s_list = getbookkeeper().newlist(self.basestringclass())
        # Force the list to be resizable because ll_splitlines doesn't
        # preallocate the list.
        s_list.listdef.listitem.resize()
        return s_list

    def method_decode(self, s_enc):
        if not s_enc.is_constant():
            raise AnnotatorError("Non-constant encoding not supported")
        enc = s_enc.const
        if enc not in ('ascii', 'latin-1', 'utf-8'):
            raise AnnotatorError("Encoding %s not supported for strings" % (enc,))
        return SomeUnicodeString(no_nul=self.no_nul)
    method_decode.can_only_throw = [UnicodeDecodeError]

class __extend__(SomeChar, SomeUnicodeCodePoint):

    def len(self):
        return immutablevalue(1)

class __extend__(SomeChar):

    def ord(self):
        return SomeInteger(nonneg=True)

    def method_isspace(self):
        return s_Bool

    def method_isalnum(self):
        return s_Bool

    def method_islower(self):
        return s_Bool

    def method_isupper(self):
        return s_Bool

    def method_lower(self):
        return self

    def method_upper(self):
        return self

class __extend__(SomeUnicodeCodePoint):

    def ord(self):
        # warning, on 32-bit with 32-bit unichars, this might return
        # negative numbers
        return SomeInteger()

class __extend__(SomeIterator):

    def iter(self):
        return self
    iter.can_only_throw = []

    def _can_only_throw(self):
        can_throw = [StopIteration]
        if isinstance(self.s_container, SomeDict):
            can_throw.append(RuntimeError)
        return can_throw

    def next(self):
        position = getbookkeeper().position_key
        if s_None.contains(self.s_container):
            return s_ImpossibleValue     # so far
        if self.variant == ("enumerate",):
            s_item = self.s_container.getanyitem(position)
            return SomeTuple((SomeInteger(nonneg=True), s_item))
        variant = self.variant
        if variant == ("reversed",):
            variant = ()
        return self.s_container.getanyitem(position, *variant)
    next.can_only_throw = _can_only_throw
    method_next = next


class __extend__(SomeInstance):
    def getattr(self, s_attr):
        if not(s_attr.is_constant() and isinstance(s_attr.const, str)):
            raise AnnotatorError("A variable argument to getattr is not RPython")
        attr = s_attr.const
        if attr == '__class__':
            return self.classdef.read_attr__class__()
        getbookkeeper().record_getattr(self.classdef.classdesc, attr)
        return self.classdef.s_getattr(attr, self.flags)
    getattr.can_only_throw = []

    def setattr(self, s_attr, s_obj):
        if s_attr.is_constant() and isinstance(s_attr.const, str):
            attr = s_attr.const
            # find the (possibly parent) class where this attr is defined
            clsdef = self.classdef.locate_attribute(attr)
            attrdef = clsdef.attrs[attr]
            attrdef.modified(clsdef)

            # if the attrdef is new, this must fail
            if attrdef.s_value.contains(s_obj):
                return
            # create or update the attribute in clsdef
            clsdef.generalize_attr(attr, s_obj)

            if isinstance(s_obj, SomeList):
                clsdef.classdesc.maybe_return_immutable_list(attr, s_obj)
        else:
            raise AnnotatorError("setattr(instance, variable_attr, value)")

    def bool_behavior(self, s):
        if not self.can_be_None:
            s.const = True

@op.len.register_transform(SomeInstance)
def len_SomeInstance(annotator, v_arg):
    get_len = op.getattr(v_arg, const('__len__'))
    return [get_len, op.simple_call(get_len.result)]

@op.iter.register_transform(SomeInstance)
def iter_SomeInstance(annotator, v_arg):
    get_iter = op.getattr(v_arg, const('__iter__'))
    return [get_iter, op.simple_call(get_iter.result)]

@op.next.register_transform(SomeInstance)
def next_SomeInstance(annotator, v_arg):
    get_next = op.getattr(v_arg, const('next'))
    return [get_next, op.simple_call(get_next.result)]

@op.getslice.register_transform(SomeInstance)
def getslice_SomeInstance(annotator, v_obj, v_start, v_stop):
    get_getslice = op.getattr(v_obj, const('__getslice__'))
    return [get_getslice, op.simple_call(get_getslice.result, v_start, v_stop)]


@op.setslice.register_transform(SomeInstance)
def setslice_SomeInstance(annotator, v_obj, v_start, v_stop, v_iterable):
    get_setslice = op.getattr(v_obj, const('__setslice__'))
    return [get_setslice,
            op.simple_call(get_setslice.result, v_start, v_stop, v_iterable)]


def _find_property_meth(s_obj, attr, meth):
    result = []
    for clsdef in s_obj.classdef.getmro():
        dct = clsdef.classdesc.classdict
        if attr not in dct:
            continue
        obj = dct[attr]
        if (not isinstance(obj, Constant) or
                not isinstance(obj.value, property)):
            return
        result.append(getattr(obj.value, meth))
    return result


@op.getattr.register_transform(SomeInstance)
def getattr_SomeInstance(annotator, v_obj, v_attr):
    s_attr = annotator.annotation(v_attr)
    if not s_attr.is_constant() or not isinstance(s_attr.const, str):
        return
    attr = s_attr.const
    getters = _find_property_meth(annotator.annotation(v_obj), attr, 'fget')
    if getters:
        if all(getters):
            get_getter = op.getattr(v_obj, const(attr + '__getter__'))
            return [get_getter, op.simple_call(get_getter.result)]
        elif not any(getters):
            raise AnnotatorError("Attribute %r is unreadable" % attr)


@op.setattr.register_transform(SomeInstance)
def setattr_SomeInstance(annotator, v_obj, v_attr, v_value):
    s_attr = annotator.annotation(v_attr)
    if not s_attr.is_constant() or not isinstance(s_attr.const, str):
        return
    attr = s_attr.const
    setters = _find_property_meth(annotator.annotation(v_obj), attr, 'fset')
    if setters:
        if all(setters):
            get_setter = op.getattr(v_obj, const(attr + '__setter__'))
            return [get_setter, op.simple_call(get_setter.result, v_value)]
        elif not any(setters):
            raise AnnotatorError("Attribute %r is unwritable" % attr)


class __extend__(SomeBuiltin):
    def call(self, args, implicit_init=False):
        args_s, kwds = args.unpack()
        # prefix keyword arguments with 's_'
        kwds_s = {}
        for key, s_value in kwds.items():
            kwds_s['s_'+key] = s_value
        return self.analyser(*args_s, **kwds_s)


class __extend__(SomeBuiltinMethod):
    def _can_only_throw(self, *args):
        analyser_func = getattr(self.analyser, 'im_func', None)
        can_only_throw = getattr(analyser_func, 'can_only_throw', None)
        if can_only_throw is None or isinstance(can_only_throw, list):
            return can_only_throw
        return can_only_throw(self.s_self, *args)

    def simple_call(self, *args):
        return self.analyser(self.s_self, *args)
    simple_call.can_only_throw = _can_only_throw

    def call(self, args, implicit_init=False):
        args_s, kwds = args.unpack()
        # prefix keyword arguments with 's_'
        kwds_s = {}
        for key, s_value in kwds.items():
            kwds_s['s_'+key] = s_value
        return self.analyser(self.s_self, *args_s, **kwds_s)


class __extend__(SomePBC):

    def getattr(self, s_attr):
        assert s_attr.is_constant()
        if s_attr.const == '__name__':
            from rpython.annotator.classdesc import ClassDesc
            if self.getKind() is ClassDesc:
                return SomeString()
        bookkeeper = getbookkeeper()
        return bookkeeper.pbc_getattr(self, s_attr)
    getattr.can_only_throw = []

    def setattr(self, s_attr, s_value):
        raise AnnotatorError("Cannot modify attribute of a pre-built constant")

    def call(self, args):
        bookkeeper = getbookkeeper()
        return bookkeeper.pbc_call(self, args)

    def bind_callables_under(self, classdef, name):
        d = [desc.bind_under(classdef, name) for desc in self.descriptions]
        return SomePBC(d, can_be_None=self.can_be_None)

    def bool_behavior(self, s):
        if not self.can_be_None:
            s.const = True

    def len(self):
        raise AnnotatorError("Cannot call len on a pbc")

class __extend__(SomeNone):
    def bind_callables_under(self, classdef, name):
        return self

    def getattr(self, s_attr):
        return s_ImpossibleValue
    getattr.can_only_throw = []

    def setattr(self, s_attr, s_value):
        return None

    def call(self, args):
        return s_ImpossibleValue

    def bool_behavior(self, s):
        s.const = False

    def len(self):
        # This None could later be generalized into a list, for example.
        # For now, we give the impossible answer (because len(None) would
        # really crash translated code).  It can be generalized later.
        return SomeImpossibleValue()

@op.issubtype.register(SomeTypeOf)
def issubtype(annotator, v_type, v_cls):
    args_v = v_type.annotation.is_type_of
    return s_isinstance(annotator, args_v[0].annotation,
                        annotator.annotation(v_cls), args_v)

#_________________________________________
# weakrefs

class __extend__(SomeWeakRef):
    def simple_call(self):
        if self.classdef is None:
            return s_None   # known to be a dead weakref
        else:
            return SomeInstance(self.classdef, can_be_None=True)