RecursionError when referencing length/mutating global string

[jpetrucciani]

Steps to reproduce

1. create a global string
2. reference it's len/__len__
3. use that value in a mutation on the global

It appears to only trigger if the reference to len appears on a separate line, and only if the mutation is in place with a slice.

Here's a snippet of code that triggers this issue:

foo = "test"


def broken():
    global foo

    bar = len(foo)
    foo = foo[bar]

Current behavior

RecursionError: maximum recursion depth exceeded with default recursion limit.

Increasing the recursion limit in the .pylintrc file like so:

[MASTER]
init-hook='import sys; sys.setrecursionlimit(100000)'

causes a segfault

Stack trace (truncated in the middle):

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/astroid/__init__.py", line 91, in _inference_tip_cached
    return iter(_cache[func, node])
KeyError: (<function register_builtin_transform.<locals>._transform_wrapper at 0x7f1dac49e840>, <Call l.7 at 0x7f1dabf3b898>)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/astroid/__init__.py", line 91, in _inference_tip_cached
    return iter(_cache[func, node])
KeyError: (<function register_builtin_transform.<locals>._transform_wrapper at 0x7f1dac49e840>, <Call l.7 at 0x7f1dabf3b898>)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/astroid/__init__.py", line 91, in _inference_tip_cached
    return iter(_cache[func, node])
KeyError: (<function register_builtin_transform.<locals>._transform_wrapper at 0x7f1dac49e840>, <Call l.7 at 0x7f1dabf3b898>)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/astroid/__init__.py", line 91, in _inference_tip_cached
    return iter(_cache[func, node])
KeyError: (<function register_builtin_transform.<locals>._transform_wrapper at 0x7f1dac49e840>, <Call l.7 at 0x7f1dabf3b898>)
...
    yield next(generator)
  File "/usr/local/lib/python3.6/site-packages/astroid/decorators.py", line 95, in wrapped
    res = next(generator)
  File "/usr/local/lib/python3.6/site-packages/astroid/bases.py", line 137, in _infer_stmts
    for inferred in stmt.infer(context=context):
  File "/usr/local/lib/python3.6/site-packages/astroid/util.py", line 160, in limit_inference
    yield from islice(iterator, size)
  File "/usr/local/lib/python3.6/site-packages/astroid/context.py", line 113, in cache_generator
    for result in generator:
  File "/usr/local/lib/python3.6/site-packages/astroid/decorators.py", line 131, in raise_if_nothing_inferred
    yield next(generator)
  File "/usr/local/lib/python3.6/site-packages/astroid/decorators.py", line 95, in wrapped
    res = next(generator)
  File "/usr/local/lib/python3.6/site-packages/astroid/bases.py", line 137, in _infer_stmts
    for inferred in stmt.infer(context=context):
  File "/usr/local/lib/python3.6/site-packages/astroid/util.py", line 160, in limit_inference
    yield from islice(iterator, size)
  File "/usr/local/lib/python3.6/site-packages/astroid/context.py", line 113, in cache_generator
    for result in generator:
  File "/usr/local/lib/python3.6/site-packages/astroid/decorators.py", line 95, in wrapped
    res = next(generator)
  File "/usr/local/lib/python3.6/site-packages/astroid/decorators.py", line 131, in raise_if_nothing_inferred
    yield next(generator)
  File "/usr/local/lib/python3.6/site-packages/astroid/inference.py", line 350, in infer_subscript
    for value in self.value.infer(context):
  File "/usr/local/lib/python3.6/site-packages/astroid/util.py", line 160, in limit_inference
    yield from islice(iterator, size)
  File "/usr/local/lib/python3.6/site-packages/astroid/context.py", line 113, in cache_generator
    for result in generator:
  File "/usr/local/lib/python3.6/site-packages/astroid/decorators.py", line 128, in raise_if_nothing_inferred
    generator = func(*args, **kwargs)
RecursionError: maximum recursion depth exceeded while calling a Python object

Expected behavior

Correct pylint analysis with no recursion errors or segfaults

pylint --version output

tried on the following versions:

pylint 2.3.1
astroid 2.2.5
Python 3.7.2 (default, Mar  5 2019, 06:22:51)
[GCC 6.3.0 20170516]

pylint 2.2.2
astroid 2.1.0
Python 3.6.8 (default, Feb  6 2019, 12:07:20)
[GCC 6.3.0 20170516]

pylint 2.3.1
astroid 2.2.5
Python 3.6.8 (default, Feb  6 2019, 12:07:20)
[GCC 6.3.0 20170516]

[PCManticore]

Yikes, thanks for the report @jpetrucciani !

[PCManticore]

Verified that this does not reproduce any longer using the latest astroid and pylint master branches.