Fix #5713: Emit used-before-assignment instead of undefined-variable when accessing unused type annotations

ChangeLog

@@ -89,6 +89,11 @@ Release date: TBA
 
 * Pyreverse - add output in mermaidjs format
 
+* Emit ``used-before-assignment`` instead of ``undefined-variable`` when attempting
+  to access unused type annotations.
+
+  Closes #5713
+
 * ``used-before-assignment`` now considers that assignments in a try block
   may not have occurred when the except or finally blocks are executed.
 

doc/whatsnew/2.13.rst

@@ -124,6 +124,11 @@ Other Changes
   Closes #4798
   Closes #5081
 
+* Emit ``used-before-assignment`` instead of ``undefined-variable`` when attempting
+  to access unused type annotations.
+
+  Closes #5713
+
 * Fixed extremely long processing of long lines with comma's.
 
   Closes #5483

pylint/checkers/variables.py

@@ -1543,7 +1543,14 @@ def _check_consumer(
                     )
 
         elif self._is_only_type_assignment(node, defstmt):
-            self.add_message("undefined-variable", args=node.name, node=node)
+            if node.scope().locals.get(node.name):
+                self.add_message(
+                    "used-before-assignment", args=node.name, node=node, confidence=HIGH
+                )
+            else:
+                self.add_message(
+                    "undefined-variable", args=node.name, node=node, confidence=HIGH
+                )
             return (VariableVisitConsumerAction.CONSUME, found_nodes)
 
         elif isinstance(defstmt, nodes.ClassDef):

tests/functional/u/undefined/undefined_variable.py

@@ -4,7 +4,7 @@
 from __future__ import print_function
 
 # pylint: disable=wrong-import-position
-from typing import TYPE_CHECKING, List
+from typing import TYPE_CHECKING
 
 DEFINED = 1
 
@@ -340,40 +340,6 @@ def decorated4(x):
     from types import GenericAlias
     object().__class_getitem__ = classmethod(GenericAlias)
 
-# Tests for annotation of variables and potentially undefinition
-
-def value_and_type_assignment():
-    """The variable assigned a value and type"""
-    variable: int = 2
-    print(variable)
-
-
-def only_type_assignment():
-    """The variable never gets assigned a value"""
-    variable: int
-    print(variable)  # [undefined-variable]
-
-
-def both_type_and_value_assignment():
-    """The variable first gets a type and subsequently a value"""
-    variable: int
-    variable = 1
-    print(variable)
-
-
-def value_assignment_after_access():
-    """The variable gets a value after it has been accessed"""
-    variable: int
-    print(variable)  # [undefined-variable]
-    variable = 1
-
-
-def value_assignment_from_iterator():
-    """The variables gets a value from an iterator"""
-    variable: int
-    for variable in (1, 2):
-        print(variable)
-
 
 GLOBAL_VAR: int
 GLOBAL_VAR_TWO: int
@@ -390,53 +356,3 @@ def global_var_mixed_assignment():
 
 GLOBAL_VAR: int
 GLOBAL_VAR_TWO: int
-
-
-def assignment_in_comprehension():
-    """A previously typed variables gets used in a comprehension. Don't crash!"""
-    some_list: List[int]
-    some_list = [1, 2, 3]
-    some_list = [i * 2 for i in some_list]
-
-
-def decorator_returning_function():
-    """A decorator that returns a wrapper function with decoupled typing"""
-    def wrapper_with_decoupled_typing():
-        print(var)
-
-    var: int
-    var = 2
-    return wrapper_with_decoupled_typing
-
-
-def decorator_returning_incorrect_function():
-    """A decorator that returns a wrapper function with decoupled typing"""
-    def wrapper_with_type_and_no_value():
-        print(var) # [undefined-variable]
-
-    var: int
-    return wrapper_with_type_and_no_value
-
-
-def typing_and_value_assignment_with_tuple_assignment():
-    """The typed variables get assigned with a tuple assignment"""
-    var_one: int
-    var_two: int
-    var_one, var_two = 1, 1
-    print(var_one)
-    print(var_two)
-
-
-def nested_class_as_return_annotation():
-    """A namedtuple as a class attribute is used as a return annotation
-
-    Taken from https://github.com/PyCQA/pylint/issues/5568"""
-    from collections import namedtuple
-
-    class MyObject:
-        Coords = namedtuple('Point', ['x', 'y'])
-
-        def my_method(self) -> Coords:
-            pass
-
-    print(MyObject)

tests/functional/u/undefined/undefined_variable.txt

@@ -32,7 +32,4 @@ undefined-variable:293:27:293:28:undefined_annotation:Undefined variable 'x':UND
 used-before-assignment:294:7:294:8:undefined_annotation:Using variable 'x' before assignment:UNDEFINED
 undefined-variable:324:11:324:12:decorated3:Undefined variable 'x':UNDEFINED
 undefined-variable:329:19:329:20:decorated4:Undefined variable 'y':UNDEFINED
-undefined-variable:354:10:354:18:only_type_assignment:Undefined variable 'variable':UNDEFINED
-undefined-variable:367:10:367:18:value_assignment_after_access:Undefined variable 'variable':UNDEFINED
-undefined-variable:384:10:384:20:global_var_mixed_assignment:Undefined variable 'GLOBAL_VAR':UNDEFINED
-undefined-variable:415:14:415:17:decorator_returning_incorrect_function.wrapper_with_type_and_no_value:Undefined variable 'var':UNDEFINED
+undefined-variable:350:10:350:20:global_var_mixed_assignment:Undefined variable 'GLOBAL_VAR':HIGH

tests/functional/u/use/used_before_assignment_type_annotations.py

@@ -0,0 +1,90 @@
+"""Tests for annotation of variables and potential use before assignment"""
+# pylint: disable=too-few-public-methods, global-variable-not-assigned
+from collections import namedtuple
+from typing import List
+
+def value_and_type_assignment():
+    """The variable assigned a value and type"""
+    variable: int = 2
+    print(variable)
+
+
+def only_type_assignment():
+    """The variable never gets assigned a value"""
+    variable: int
+    print(variable)  # [used-before-assignment]
+
+
+def both_type_and_value_assignment():
+    """The variable first gets a type and subsequently a value"""
+    variable: int
+    variable = 1
+    print(variable)
+
+
+def value_assignment_after_access():
+    """The variable gets a value after it has been accessed"""
+    variable: int
+    print(variable)  # [used-before-assignment]
+    variable = 1
+
+
+def value_assignment_from_iterator():
+    """The variables gets a value from an iterator"""
+    variable: int
+    for variable in (1, 2):
+        print(variable)
+
+
+def assignment_in_comprehension():
+    """A previously typed variables gets used in a comprehension. Don't crash!"""
+    some_list: List[int]
+    some_list = [1, 2, 3]
+    some_list = [i * 2 for i in some_list]
+
+
+def decorator_returning_function():
+    """A decorator that returns a wrapper function with decoupled typing"""
+    def wrapper_with_decoupled_typing():
+        print(var)
+
+    var: int
+    var = 2
+    return wrapper_with_decoupled_typing
+
+
+def decorator_returning_incorrect_function():
+    """A decorator that returns a wrapper function with decoupled typing"""
+    def wrapper_with_type_and_no_value():
+        # This emits NameError rather than UnboundLocalError, so
+        # undefined-variable is okay, even though the traceback refers
+        # to "free variable 'var' referenced before assignment"
+        print(var) # [undefined-variable]
+
+    var: int
+    return wrapper_with_type_and_no_value
+
+
+def typing_and_value_assignment_with_tuple_assignment():
+    """The typed variables get assigned with a tuple assignment"""
+    var_one: int
+    var_two: int
+    var_one, var_two = 1, 1
+    print(var_one)
+    print(var_two)
+
+
+def nested_class_as_return_annotation():
+    """A namedtuple as a class attribute is used as a return annotation
+
+    Taken from https://github.com/PyCQA/pylint/issues/5568"""
+    class MyObject:
+        """namedtuple as class attribute"""
+        Coords = namedtuple('Point', ['x', 'y'])
+
+        def my_method(self) -> Coords:
+            """Return annotation is valid"""
+            # pylint: disable=unnecessary-pass
+            pass
+
+    print(MyObject)

tests/functional/u/use/used_before_assignment_type_annotations.txt

@@ -0,0 +1,3 @@
+used-before-assignment:15:10:15:18:only_type_assignment:Using variable 'variable' before assignment:HIGH
+used-before-assignment:28:10:28:18:value_assignment_after_access:Using variable 'variable' before assignment:HIGH
+undefined-variable:62:14:62:17:decorator_returning_incorrect_function.wrapper_with_type_and_no_value:Undefined variable 'var':HIGH