From 5fee33ffcd52a9a078922a3ab881b0d165c32bfa Mon Sep 17 00:00:00 2001
From: Jacob Walls <jacobtylerwalls@gmail.com>
Date: Fri, 13 May 2022 09:40:25 -0400
Subject: [PATCH] Fix a crash in `unnecessary-list-index-lookup` when
 incorrectly using `enumerate()` (#6604)

---
 ChangeLog                                                    | 5 +++++
 doc/whatsnew/2.13.rst                                        | 4 ++++
 pylint/checkers/refactoring/refactoring_checker.py           | 1 +
 .../u/unnecessary/unnecessary_list_index_lookup.py           | 4 ++++
 4 files changed, 14 insertions(+)

diff --git a/ChangeLog b/ChangeLog
index e1d48fd2cc..72ac6c80e6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -344,6 +344,11 @@ Release date: TBA
 
   Closes #6557
 
+* Fix a crash in ``unnecessary-list-index-lookup`` when incorrectly passing no
+  arguments to ``enumerate()``.
+
+  Closes #6603
+
 * Fix a crash when accessing ``__code__`` and assigning it to a variable.
 
   Closes #6539
diff --git a/doc/whatsnew/2.13.rst b/doc/whatsnew/2.13.rst
index 080aa42345..fd5ce73f6f 100644
--- a/doc/whatsnew/2.13.rst
+++ b/doc/whatsnew/2.13.rst
@@ -644,6 +644,10 @@ Other Changes
 
   Closes #6414
 
+* Fix a crash in ``unnecessary-list-index-lookup`` when incorrectly passing no
+  arguments to ``enumerate()``.
+
+  Closes #6603
 
 * Fix false positives for ``no-name-in-module`` and ``import-error`` for ``numpy.distutils``
   and ``pydantic``.
diff --git a/pylint/checkers/refactoring/refactoring_checker.py b/pylint/checkers/refactoring/refactoring_checker.py
index 586564f8c1..e01eaf3b08 100644
--- a/pylint/checkers/refactoring/refactoring_checker.py
+++ b/pylint/checkers/refactoring/refactoring_checker.py
@@ -1996,6 +1996,7 @@ def _check_unnecessary_list_index_lookup(
             not isinstance(node.iter, nodes.Call)
             or not isinstance(node.iter.func, nodes.Name)
             or not node.iter.func.name == "enumerate"
+            or not node.iter.args
             or not isinstance(node.iter.args[0], nodes.Name)
         ):
             return
diff --git a/tests/functional/u/unnecessary/unnecessary_list_index_lookup.py b/tests/functional/u/unnecessary/unnecessary_list_index_lookup.py
index abdd64d70a..ba99d3b9ba 100644
--- a/tests/functional/u/unnecessary/unnecessary_list_index_lookup.py
+++ b/tests/functional/u/unnecessary/unnecessary_list_index_lookup.py
@@ -49,3 +49,7 @@ def process_list_again(data):
 pairs = [(0, 0)]
 for i, (a, b) in enumerate(pairs):
     print(pairs[i][0])
+
+# Regression test for https://github.com/PyCQA/pylint/issues/6603
+for i, num in enumerate():  # raises TypeError, but shouldn't crash pylint
+    pass