Handle redefinitions in case of type checking imports.

Close #2834

ChangeLog

@@ -16,6 +16,10 @@ Release date: TBA
 
   Close #2540
 
+* Handle redefinitions in case of type checking imports.
+
+  Close #2834
+
 * Added a new check, ``consider-using-sys-exit``
 
   This check is emitted when we detect that a quit() or exit() is invoked

pylint/checkers/variables.py

@@ -942,6 +942,15 @@ def visit_functiondef(self, node):
                     # It is a __future__ directive, not a symbol.
                     continue
 
+                # Do not take in account redefined names for the purpose
+                # of type checking.:
+                if any(
+                    isinstance(definition.parent, astroid.If)
+                    and definition.parent.test.as_string() in TYPING_TYPE_CHECKS_GUARDS
+                    for definition in globs[name]
+                ):
+                    continue
+
                 line = definition.fromlineno
                 if not self._is_name_ignored(stmt, name):
                     self.add_message(

tests/functional/r/redefined_outer_name_type_checking.py

@@ -0,0 +1,20 @@
+# pylint: disable=missing-module-docstring,missing-class-docstring,too-few-public-methods
+# pylint: disable=no-self-use,missing-function-docstring
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+
+class Cls:
+    def func(self, stuff: defaultdict):
+        # This import makes the definition work.
+        from collections import defaultdict
+
+        obj = defaultdict()
+        obj.update(stuff)
+        return obj
+
+
+if TYPE_CHECKING:
+    # This import makes the annotations work.
+    from collections import defaultdict

tests/functional/r/redefined_outer_name_type_checking.rc

@@ -0,0 +1,2 @@
+[testoptions]
+min_pyver=3.7