Make operations on None fall back on object (#1835)

Author: ddfisher

mypy/checkmember.py

@@ -18,11 +18,15 @@
 from mypy import subtypes
 
 
-def analyze_member_access(name: str, typ: Type, node: Context, is_lvalue: bool,
+def analyze_member_access(name: str,
+                          typ: Type,
+                          node: Context,
+                          is_lvalue: bool,
                           is_super: bool,
                           builtin_type: Callable[[str], Instance],
                           not_ready_callback: Callable[[str, Context], None],
-                          msg: MessageBuilder, override_info: TypeInfo = None,
+                          msg: MessageBuilder,
+                          override_info: TypeInfo = None,
                           report_type: Type = None) -> Type:
     """Analyse attribute access.
 
@@ -72,6 +76,11 @@ def analyze_member_access(name: str, typ: Type, node: Context, is_lvalue: bool,
     elif isinstance(typ, AnyType):
         # The base object has dynamic type.
         return AnyType()
+    elif isinstance(typ, NoneTyp):
+        # The only attribute NoneType has are those it inherits from object
+        return analyze_member_access(name, builtin_type('builtins.object'), node, is_lvalue,
+                                     is_super, builtin_type, not_ready_callback, msg,
+                                     report_type=report_type)
     elif isinstance(typ, UnionType):
         # The base object has dynamic type.
         msg.disable_type_names += 1

test-data/unit/check-expressions.test

@@ -1493,3 +1493,11 @@ reveal_type("foo") # E: Argument 1 to "reveal_type" has incompatible type "str";
 [case testRevealTypeVar]
 reveal_type = 1
 1 + "foo" # E: Unsupported operand types for + ("int" and "str")
+
+[case testEqNone]
+None == None
+[builtins fixtures/ops.py]
+
+[case testLtNone]
+None < None  # E: Unsupported left operand type for < (None)
+[builtins fixtures/ops.py]