Fix #1555: Fix false negatives for no-member from self-referencing assignments

ChangeLog

@@ -9,7 +9,10 @@ Release date: TBA
 ..
   Put new features here and also in 'doc/whatsnew/2.14.rst'
 
+* Fix false negative for ``no-member`` when attempting to assign an instance
+  attribute to itself without any prior assignment.
 
+  Closes #1555
 
 ..
   Insert your changelog randomly, it will reduce merge conflicts

doc/whatsnew/2.14.rst

@@ -23,3 +23,8 @@ Extensions
 
 Other Changes
 =============
+
+* Fix false negative for ``no-member`` when attempting to assign an instance
+  attribute to itself without any prior assignment.
+
+  Closes #1555

pylint/checkers/typecheck.py

@@ -1007,15 +1007,7 @@ def visit_attribute(self, node: nodes.Attribute) -> None:
                 return
 
             try:
-                if not [
-                    n
-                    for n in owner.getattr(node.attrname)
-                    if not isinstance(n.statement(future=True), nodes.AugAssign)
-                ]:
-                    missingattr.add((owner, name))
-                    continue
-            except astroid.exceptions.StatementMissing:
-                continue
+                attr_nodes = owner.getattr(node.attrname)
             except AttributeError:
                 continue
             except astroid.DuplicateBasesError:
@@ -1039,6 +1031,24 @@ def visit_attribute(self, node: nodes.Attribute) -> None:
                     continue
                 missingattr.add((owner, name))
                 continue
+            else:
+                for attr_node in attr_nodes:
+                    attr_parent = attr_node.parent
+                    # Skip augmented assignments
+                    try:
+                        if isinstance(
+                            attr_node.statement(future=True), nodes.AugAssign
+                        ):
+                            continue
+                    except astroid.exceptions.StatementMissing:
+                        break
+                    # Skip self-referencing assignments
+                    if attr_parent is node.parent:
+                        continue
+                    break
+                else:
+                    missingattr.add((owner, name))
+                    continue
             # stop on the first found
             break
         else:

tests/functional/n/no/no_member_assign_same_line.py

@@ -0,0 +1,37 @@
+"""Tests for no-member for self-referencing instance attributes
+See https://github.com/PyCQA/pylint/issues/1555
+"""
+# pylint: disable=too-few-public-methods
+
+
+class ClassWithMember:
+    """Member defined in superclass."""
+    def __init__(self):
+        self.member = True
+
+
+class AssignMemberInSameLine:
+    """This class attempts to assign and access a member in the same line."""
+    def __init__(self):
+        self.member = self.member  # [no-member]
+
+
+class AssignMemberInSameLineAfterTypeAnnotation:
+    """This might emit a message like `maybe-no-member` in the future."""
+    def __init__(self):
+        self.member: bool
+        self.member = self.member
+
+
+class AssignMemberFromSuper1(ClassWithMember):
+    """This assignment is valid due to inheritance."""
+    def __init__(self):
+        self.member = self.member
+        super().__init__()
+
+
+class AssignMemberFromSuper2(ClassWithMember):
+    """This assignment is valid due to inheritance."""
+    def __init__(self):
+        super().__init__()
+        self.member = self.member

tests/functional/n/no/no_member_assign_same_line.txt

@@ -0,0 +1 @@
+no-member:16:22:16:33:AssignMemberInSameLine.__init__:Instance of 'AssignMemberInSameLine' has no 'member' member:INFERENCE