[Backport maintenance/3.2.x] Fix a crash in undefined-loop-variable…

… with `enumerate()` (#9877) * Fix a crash in `undefined-loop-variable` with `enumerate()` (#9876) (cherry picked from commit cb6db06) Co-authored-by: Jacob Walls <[email protected]>
pylint-dev · Aug 16, 2024 · b4c2951 · b4c2951
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diff --git a/doc/whatsnew/fragments/9875.bugfix b/doc/whatsnew/fragments/9875.bugfix
@@ -0,0 +1,3 @@
+Fix a crash in ``undefined-loop-variable`` when providing the ``iterable`` argument to ``enumerate()``.
+
+Closes #9875
diff --git a/pylint/checkers/variables.py b/pylint/checkers/variables.py
@@ -2683,7 +2683,7 @@ def _loopvar_name(self, node: astroid.Name) -> None:
                 likely_call = assign.iter
                 if isinstance(assign.iter, nodes.IfExp):
                     likely_call = assign.iter.body
-                if isinstance(likely_call, nodes.Call):
+                if isinstance(likely_call, nodes.Call) and likely_call.args:
                     inferred = next(likely_call.args[0].infer())
         except astroid.InferenceError:
             self.add_message("undefined-loop-variable", args=node.name, node=node)

diff --git a/tests/functional/r/regression_02/regression_9875_enumerate.py b/tests/functional/r/regression_02/regression_9875_enumerate.py
@@ -0,0 +1,7 @@
+"""https://github.com/pylint-dev/pylint/issues/9875"""
+# value = 0
+for idx, value in enumerate(iterable=[1, 2, 3]):
+    print(f'{idx=} {value=}')
+# +1: [undefined-loop-variable, undefined-loop-variable]
+for idx, value in enumerate(iterable=[value-1, value-2*1]):
+    print(f'{idx=} {value=}')
diff --git a/tests/functional/r/regression_02/regression_9875_enumerate.txt b/tests/functional/r/regression_02/regression_9875_enumerate.txt
@@ -0,0 +1,2 @@
+undefined-loop-variable:6:38:6:43::Using possibly undefined loop variable 'value':UNDEFINED
+undefined-loop-variable:6:47:6:52::Using possibly undefined loop variable 'value':UNDEFINED
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,3 @@
		Fix a crash in ``undefined-loop-variable`` when providing the ``iterable`` argument to ``enumerate()``.

		Closes #9875
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		undefined-loop-variable:6:38:6:43::Using possibly undefined loop variable 'value':UNDEFINED
		undefined-loop-variable:6:47:6:52::Using possibly undefined loop variable 'value':UNDEFINED