KeyError while linting black's blib2to3/pygram.py

[Pierre-Sassoulas]

Bug description

While parsing https://github.com/psf/black/blob/main/src/blib2to3/pygram.py getting an exception on node <Name.python_grammar l.175 at 0x7ff390d60c40>

pylint crashed with a KeyError and with the following stacktrace:

Traceback (most recent call last):
  File "/home/pierre/pylint/pylint/lint/pylinter.py", line 1028, in _check_files
    self._check_file(get_ast, check_astroid_module, file)
  File "/home/pierre/pylint/pylint/lint/pylinter.py", line 1063, in _check_file
    check_astroid_module(ast_node)
  File "/home/pierre/pylint/pylint/lint/pylinter.py", line 1199, in check_astroid_module
    retval = self._check_astroid_module(
  File "/home/pierre/pylint/pylint/lint/pylinter.py", line 1246, in _check_astroid_module
    walker.walk(node)
  File "/home/pierre/pylint/pylint/utils/ast_walker.py", line 78, in walk
    self.walk(child)
  File "/home/pierre/pylint/pylint/utils/ast_walker.py", line 78, in walk
    self.walk(child)
  File "/home/pierre/pylint/pylint/utils/ast_walker.py", line 78, in walk
    self.walk(child)
  [Previous line repeated 1 more time]
  File "/home/pierre/pylint/pylint/utils/ast_walker.py", line 75, in walk
    callback(astroid)
  File "/home/pierre/pylint/pylint/checkers/variables.py", line 1189, in visit_name
    elif self._is_only_type_assignment(node, name, defstmt):
  File "/home/pierre/pylint/pylint/checkers/variables.py", line 1560, in _is_only_type_assignment
    for ref_node in node.scope().locals[name][1:]:
KeyError: 'python_grammar'

Command used

pylint black/src/blib2to3/pygram.py

Pylint output

************* Module blib2to3.pygram
.pylint_primer_tests/black/src/blib2to3/pygram.py:24:0: R0205: Class 'Symbols' inherits from object, can be safely removed from bases in python3 (useless-object-inheritance)
.pylint_primer_tests/black/src/blib2to3/pygram.py:158:4: W0603: Using the global statement (global-statement)
.pylint_primer_tests/black/src/blib2to3/pygram.py:159:4: W0603: Using the global statement (global-statement)
.pylint_primer_tests/black/src/blib2to3/pygram.py:160:4: W0603: Using the global statement (global-statement)
.pylint_primer_tests/black/src/blib2to3/pygram.py:161:4: W0603: Using the global statement (global-statement)
.pylint_primer_tests/black/src/blib2to3/pygram.py:162:4: W0603: Using the global statement (global-statement)
.pylint_primer_tests/black/src/blib2to3/pygram.py:163:4: W0603: Using the global statement (global-statement)
.pylint_primer_tests/black/src/blib2to3/pygram.py:164:4: W0603: Using the global statement (global-statement)
Exception on node <Name.python_grammar l.175 at 0x7ff390d60c40> in file '/home/pierre/pylint/.pylint_primer_tests/black/src/blib2to3/pygram.py'
Traceback (most recent call last):
  File "/home/pierre/pylint/pylint/utils/ast_walker.py", line 75, in walk
    callback(astroid)
  File "/home/pierre/pylint/pylint/checkers/variables.py", line 1189, in visit_name
    elif self._is_only_type_assignment(node, name, defstmt):
  File "/home/pierre/pylint/pylint/checkers/variables.py", line 1560, in _is_only_type_assignment
    for ref_node in node.scope().locals[name][1:]:
KeyError: 'python_grammar'
.pylint_primer_tests/black/src/blib2to3/pygram.py:1:0: F0001: Fatal error while checking '.pylint_primer_tests/black/src/blib2to3/pygram.py'. Please open an issue in our bug tracker so we address this. There is a pre-filled template that you can use in '/home/pierre/.cache/pylint/pylint-crash-2021-10-17-15.txt'. (fatal)

Expected behavior

Pylint should handle the case where the name does not exists without crash.

Pylint version

pylint 2.11.2-dev0
astroid 2.8.3
Python 3.8.10 (default, Sep 28 2021, 16:10:42) 
[GCC 9.3.0]

[cdce8p]

Might be related to #5162 although I'm not sure if it's a duplicate or another issue.

[cdce8p]

/CC: @DanielNoord

[Pierre-Sassoulas]

Yeah sorry, it's a duplicate clearly.

[cdce8p]

Yeah sorry, it's a duplicate clearly.

Not from the initial report. However I mentioned it in a comment without know about it 😅 #5162 (comment)
Let's close this one and continue to track it in #5162