Allow import aliases to exempt import-error when used in type ann…

…otations.

Close #3178

ChangeLog

@@ -16,6 +16,10 @@ Release date: TBA
 
   Close #3235
 
+* Allow import aliases to exempt ``import-error`` when used in type annotations.
+
+  Close #3178
+
 * ``Ellipsis` is exempted from ``multiple-statements`` for function overloads.
 
   Close #3224

pylint/checkers/variables.py

@@ -1879,6 +1879,10 @@ def _check_imports(self, not_consumed):
                     continue
                 checked.add(real_name)
 
+                is_type_annotation_import = (
+                    imported_name in self._type_annotation_names
+                    or as_name in self._type_annotation_names
+                )
                 if isinstance(stmt, astroid.Import) or (
                     isinstance(stmt, astroid.ImportFrom) and not stmt.modname
                 ):
@@ -1889,7 +1893,7 @@ def _check_imports(self, not_consumed):
                         # because they can be imported for exporting.
                         continue
 
-                    if imported_name in self._type_annotation_names:
+                    if is_type_annotation_import:
                         # Most likely a typing import if it wasn't used so far.
                         continue
 
@@ -1912,7 +1916,7 @@ def _check_imports(self, not_consumed):
                         # __future__ import in another module.
                         continue
 
-                    if imported_name in self._type_annotation_names:
+                    if is_type_annotation_import:
                         # Most likely a typing import if it wasn't used so far.
                         continue
 

tests/functional/u/unused_typing_imports.py

@@ -7,6 +7,7 @@
 
 import re
 import typing
+from collections import Counter as CollectionCounter
 from collections import defaultdict
 from datetime import datetime
 from typing import (
@@ -74,5 +75,11 @@ def magic(alpha, beta, gamma):
 
 
 def unused_assignment_import():
-    foo_or_bar = defaultdict(int)  # type: defaultdict
+    foo_or_bar = 42  # type: defaultdict
     return foo_or_bar
+
+
+def unused_reassigned_import(counter):
+    # type: (CollectionCounter) -> int
+    print(counter)
+    return 42