Fix false positive for undefined-loop-variable with enumerate() (#6602)

Co-authored-by: Pierre Sassoulas <[email protected]>

Author: jacobtylerwalls

ChangeLog

@@ -41,6 +41,10 @@ Release date: TBA
 
   Closes #6539
 
+* Fix a false positive for ``undefined-loop-variable`` when using ``enumerate()``.
+
+  Closes #6593
+
 
 What's New in Pylint 2.13.8?
 ============================

doc/whatsnew/2.13.rst

@@ -657,3 +657,7 @@ Other Changes
 * Fix a crash in ``unnecessary-dict-index-lookup`` when subscripting an attribute.
 
   Closes #6557
+
+* Fix a false positive for ``undefined-loop-variable`` when using ``enumerate()``.
+
+  Closes #6593

pylint/checkers/variables.py

@@ -2265,6 +2265,13 @@ def _loopvar_name(self, node: astroid.Name) -> None:
         # For functions we can do more by inferring the length of the itered object
         try:
             inferred = next(assign.iter.infer())
+            # Prefer the target of enumerate() rather than the enumerate object itself
+            if (
+                isinstance(inferred, astroid.Instance)
+                and inferred.qname() == "builtins.enumerate"
+                and assign.iter.args
+            ):
+                inferred = next(assign.iter.args[0].infer())
         except astroid.InferenceError:
             self.add_message("undefined-loop-variable", args=node.name, node=node)
         else:

tests/functional/u/undefined/undefined_loop_variable.py

@@ -139,3 +139,10 @@ def variable_name_assigned_in_body_of_second_loop():
         alias = True
         if alias:
             print(alias)
+
+
+def use_enumerate():
+    """https://github.com/PyCQA/pylint/issues/6593"""
+    for i, num in enumerate(range(3)):
+        pass
+    print(i, num)