Enable strict_bytes by default

mypy/main.py

@@ -870,9 +870,9 @@ def add_invertible_flag(
     )
 
     add_invertible_flag(
-        "--strict-bytes",
-        default=False,
-        strict_flag=False,
+        "--no-strict-bytes",
+        default=True,
+        dest="strict_bytes",
         help="Disable treating bytearray and memoryview as subtypes of bytes",
         group=strictness_group,
     )

mypy/options.py

@@ -217,7 +217,7 @@ def __init__(self) -> None:
         self.strict_equality = False
 
         # Disable treating bytearray and memoryview as subtypes of bytes
-        self.strict_bytes = False
+        self.strict_bytes = True
 
         # Deprecated, use extra_checks instead.
         self.strict_concatenate = False
@@ -386,8 +386,8 @@ def __init__(self) -> None:
         # (undocumented feature).
         self.export_ref_info = False
 
-        self.disable_bytearray_promotion = False
-        self.disable_memoryview_promotion = False
+        self.disable_bytearray_promotion = True
+        self.disable_memoryview_promotion = True
         self.force_uppercase_builtins = False
         self.force_union_syntax = False
 

mypy/test/testargs.py

@@ -12,7 +12,7 @@
 
 from mypy.main import infer_python_executable, process_options
 from mypy.options import Options
-from mypy.test.helpers import Suite, assert_equal
+from mypy.test.helpers import Suite
 
 
 class ArgSuite(Suite):
@@ -21,7 +21,7 @@ def test_coherence(self) -> None:
         _, parsed_options = process_options([], require_targets=False)
         # FIX: test this too. Requires changing working dir to avoid finding 'setup.cfg'
         options.config_file = parsed_options.config_file
-        assert_equal(options.snapshot(), parsed_options.snapshot())
+        assert options.snapshot() == parsed_options.snapshot()
 
     def test_executable_inference(self) -> None:
         """Test the --python-executable flag with --python-version"""