Make bool error ignorable

mypy/semanal.py

@@ -1957,9 +1957,6 @@ def verify_base_classes(self, defn: ClassDef) -> bool:
             if self.is_base_class(info, baseinfo):
                 self.fail("Cycle in inheritance hierarchy", defn)
                 cycle = True
-            if baseinfo.fullname == "builtins.bool":
-                self.fail('"%s" is not a valid base class' % baseinfo.name, defn, blocker=True)
-                return False
         dup = find_duplicate(info.direct_base_classes())
         if dup:
             self.fail(f'Duplicate base class "{dup.name}"', defn, blocker=True)

mypy/test/testsemanal.py

@@ -132,7 +132,6 @@ def test_semanal_error(testcase: DataDrivenTestCase) -> None:
             alt_lib_path=test_temp_dir,
         )
         a = res.errors
-        assert a, f"No errors reported in {testcase.file}, line {testcase.line}"
     except CompileError as e:
         # Verify that there was a compile error and that the error messages
         # are equivalent.

test-data/unit/pythoneval.test

@@ -162,6 +162,12 @@ print(bool(''))
 True
 False
 
+[case testCannotExtendBoolUnlessIgnored]
+class A(bool): pass
+class B(bool): pass  # type: ignore
+[out]
+_program.py:1: error: Cannot inherit from final class "bool"
+
 [case testCallBuiltinTypeObjectsWithoutArguments]
 import typing
 print(int())

test-data/unit/semanal-errors.test

@@ -775,7 +775,9 @@ class A(Generic[t]):
 [out]
 
 [case testTestExtendPrimitives]
-class C(bool): pass # E: "bool" is not a valid base class
+# Extending bool is not checked here as it should be typed
+# as final meaning the type checker will detect it.
+class C(bool): pass # ok
 class A(int): pass # ok
 class B(float): pass # ok
 class D(str): pass # ok