Issue1455153

The attached set of patches are an attempt at fixes for
several bugs encountered while executing parts of
test_descr.py from cpython 2.3.5 against jython cvs.

Since test_descr.py is long and many other parts still
fail, i've extracted/simplified the tests of interest
and attached them as a stand-alone script.

The specific bugs are a recursion/stack-overflow in
dict subtypes that override parents __getitem__(),
list's __getslice__()/__setslice__() methods not
accepting the 2/3 argument forms, and an incorrect
error type being raised for certain dict constructor args.

I'm not certain its all correct, review appreciated.

- kz

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The overflow fix breaks test_descrtut -- but I'm accepting
the rest.

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That is to say I'm accepting the fixes, though I am going to
apply them to the templating code and not directly -- I've
sent an email to jython-dev and to you on the subject.  I'll
reprint here for reference:

note that in some cases instead of applying them directly to
the source code under jython/src/... I applied them to the
source generation code in sandbox/jt.  So the changes to
derived classes went into object.derived, and the changes to
the number of args sequences can take went into seq.expose.
 Followed by running:

python gderived.py dict.derived >
../../jython/src/org/python/core/PyDictionaryDerived.java

python gexpose.py dict.expose
../../jython/src/org/python/core/PyDictionary.java


python gderived.py list.derived >
../../jython/src/org/python/core/PyListDerived.java

python gexpose.py list.expose
../../jython/src/org/python/core/PyList.java

I know the templating code is pretty much undocumented at
this point, hopefully I'll eventually find time to produce
some docs for it...

I wasn't able to apply the change from looking up
__finditem__ to looking up __getitem__ (which causes the
stack overflow) because it broke test_descrtut.py, which
worked before.  Perhaps the test:

def t4():
    """
    jython recursively calls __getitem__ until it
    blows the stack
    """
    class C(dict):
        def __getitem__(self, key):
            return self.get(key)

    d = C()
    if not (d[1] == None):
        print "Failure"
    else:
        print "Success"

exposes an implementation detail... since to my eyes an
overflow doesn't seem to be surprising when a call to
self.__getitem__(key) calls self.get(key).  In any case,
we'd have to find a way so that both the test_descr test and
the test_descrtut test can pass.  The part of test_descrtut
that fails is 

    >>> exec "print foo" in a

on line 83

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r2957/2958 should finish addressing this on the trunk.

I made jython more similar to CPython. get will not delegate
to an overriden __getitem__ by default. We are too incosistent 
in doing that overall to make this worth the difference
vs cpython.

I had to fix other stack overflows/infinite recursion related
on how str/unicode and tuples didn't follow the lead of
lists in using PySequence without getting into trouble.

I think this is finished.  Closing.