fix: handle for-loop variable shadowing correctly (#10569) (#10571)

(cherry picked from commit ed6b306) Signed-off-by: Emmanuel Ferdman <emmanuelferdman@gmail.com> Co-authored-by: Emmanuel Ferdman <emmanuelferdman@gmail.com>

Author: pylint-backport[bot]

doc/whatsnew/fragments/10562.bugfix

@@ -0,0 +1,3 @@
+Fix false positive ``undefined-variable`` (E0602) for for-loop variable shadowing patterns like ``for item in item:`` when the variable was previously defined.
+
+Closes #10562

pylint/checkers/variables.py

@@ -629,7 +629,12 @@ def get_next_to_consume(self, node: nodes.Name) -> list[nodes.NodeNG] | None:
  and parent_node.iter == node
  and parent_node.target in found_nodes
  ):
- found_nodes = None
+ # Only filter out the for-loop target if there are other definitions besides the target
+ other_definitions = [fn for fn in found_nodes if fn != parent_node.target]
+ if other_definitions:
+ found_nodes = other_definitions
+ else:
+ found_nodes = None
 
  # Before filtering, check that this node's name is not a nonlocal
  if any(

tests/functional/f/for_loop_variable_shadowing.py

@@ -0,0 +1,10 @@
+# pylint: disable=missing-module-docstring
+
+# Should not trigger undefined-variable (#10562)
+item = (1, 2, 3)
+for item in item:
+ print(item)
+
+# Should trigger undefined-variable
+for iteree in iteree: # [undefined-variable]
+ print(iteree)

tests/functional/f/for_loop_variable_shadowing.txt

@@ -0,0 +1 @@
+undefined-variable:9:14:9:20::Undefined variable 'iteree':UNDEFINED