None.__bool__ returns Literal[False] (#11290)

Closes #11287

Author: sobolevn

mypy/checkmember.py

@@ -317,17 +317,18 @@ def analyze_union_member_access(name: str, typ: UnionType, mx: MemberContext) ->
 
 
 def analyze_none_member_access(name: str, typ: NoneType, mx: MemberContext) -> Type:
-    if mx.chk.should_suppress_optional_error([typ]):
-        return AnyType(TypeOfAny.from_error)
     is_python_3 = mx.chk.options.python_version[0] >= 3
     # In Python 2 "None" has exactly the same attributes as "object". Python 3 adds a single
     # extra attribute, "__bool__".
     if is_python_3 and name == '__bool__':
+        literal_false = LiteralType(False, fallback=mx.named_type('builtins.bool'))
         return CallableType(arg_types=[],
                             arg_kinds=[],
                             arg_names=[],
-                            ret_type=mx.named_type('builtins.bool'),
+                            ret_type=literal_false,
                             fallback=mx.named_type('builtins.function'))
+    elif mx.chk.should_suppress_optional_error([typ]):
+        return AnyType(TypeOfAny.from_error)
     else:
         return _analyze_member_access(name, mx.named_type('builtins.object'), mx)
 

test-data/unit/check-basic.test

@@ -401,9 +401,18 @@ def foo(
 [case testNoneHasBool]
 none = None
 b = none.__bool__()
-reveal_type(b)  # N: Revealed type is "builtins.bool"
+reveal_type(b)  # N: Revealed type is "Literal[False]"
 [builtins fixtures/bool.pyi]
 
+[case testNoneHasBoolShowNoneErrorsFalse]
+none = None
+b = none.__bool__()
+reveal_type(b)  # N: Revealed type is "Literal[False]"
+[builtins fixtures/bool.pyi]
+[file mypy.ini]
+\[mypy]
+show_none_errors = False
+
 [case testAssignmentInvariantNoteForList]
 from typing import List
 x: List[int]