Prevent assignment to None for non-Optional class variables

Python 3.5 has been dead for a long time

Author: hauntsaninja

mypy/checker.py

@@ -3209,7 +3209,7 @@ def visit_assignment_stmt(self, s: AssignmentStmt) -> None:
         # as X | Y.
         if not (s.is_alias_def and self.is_stub):
             with self.enter_final_context(s.is_final_def):
-                self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None, s.new_syntax)
+                self.check_assignment(s.lvalues[-1], s.rvalue, s.type is None)
 
         if s.is_alias_def:
             self.check_type_alias_rvalue(s)
@@ -3257,11 +3257,7 @@ def check_type_alias_rvalue(self, s: AssignmentStmt) -> None:
         self.store_type(s.lvalues[-1], alias_type)
 
     def check_assignment(
-        self,
-        lvalue: Lvalue,
-        rvalue: Expression,
-        infer_lvalue_type: bool = True,
-        new_syntax: bool = False,
+        self, lvalue: Lvalue, rvalue: Expression, infer_lvalue_type: bool = True
     ) -> None:
         """Type check a single assignment: lvalue = rvalue."""
         if isinstance(lvalue, (TupleExpr, ListExpr)):
@@ -3339,15 +3335,6 @@ def check_assignment(
                             # We are replacing partial<None> now, so the variable type
                             # should remain optional.
                             self.set_inferred_type(var, lvalue, make_optional_type(fallback))
-                elif (
-                    is_literal_none(rvalue)
-                    and isinstance(lvalue, NameExpr)
-                    and isinstance(lvalue.node, Var)
-                    and lvalue.node.is_initialized_in_class
-                    and not new_syntax
-                ):
-                    # Allow None's to be assigned to class variables with non-Optional types.
-                    rvalue_type = lvalue_type
                 elif (
                     isinstance(lvalue, MemberExpr) and lvalue.kind is None
                 ):  # Ignore member access to modules
@@ -5108,9 +5095,7 @@ def visit_operator_assignment_stmt(self, s: OperatorAssignmentStmt) -> None:
             # There is no __ifoo__, treat as x = x <foo> y
             expr = OpExpr(s.op, s.lvalue, s.rvalue)
             expr.set_line(s)
-            self.check_assignment(
-                lvalue=s.lvalue, rvalue=expr, infer_lvalue_type=True, new_syntax=False
-            )
+            self.check_assignment(lvalue=s.lvalue, rvalue=expr, infer_lvalue_type=True)
         self.check_final(s)
 
     def visit_assert_stmt(self, s: AssertStmt) -> None: