no-member regression in 2.5.7

[chrisburr]

Steps to reproduce

Create a file names example.py:

def S_OK(value=None):
  return {'OK': True, 'Value': value}


class FooBar:
  def __init__(self):
    self.__initStatus = S_OK()

  def check(self, result):
    return result["Value"]

  def load(self):
    if not self.__initStatus['OK']:
      return self.__initStatus
    return S_OK((None, ["Hello"]))

  def connect(self):
    _, mylist = self.check(self.load())
    mylist.append("world")

Current behavior

With astroid 2.5.7:

$ pylint -E example.py
************* Module example
example.py:19:4: E1101: Instance of 'str' has no 'append' member (no-member)

Expected behavior

With astroid 2.5.6:

$ pylint -E example.py

[nelfin]

This appears to be a failure of inference for the return value of S_OK in your example. There were some fixes around sequenc and mapping types if I remember correctly. Given

import astroid
good, fail = astroid.extract_node("""
def OK():
    return {'constant': True}

def NOT_OK(value=None):
    return {'constant': value}

def check(result):
    return result["constant"]

check(OK()) #@
check(NOT_OK()) #@
""")
print(next(good.infer()))
print(next(fail.infer()))

astroid-2.5.6:

Const.bool(value=True)
Uninferable

astroid-2.5.7:

Const.bool(value=True)
Dict.dict(items=[ ( <Const.str l.6 at 0x7fe81093cdf0>,
              <Name.value l.6 at 0x7fe8105ca550>)])