Apply --strict-equality special-casing for bytes and bytearray on Pyt…

…hon 2 (#7493)

Fixes #7465

The previous fix only worked on Python 3.

mypy/checkexpr.py

@@ -2136,8 +2136,9 @@ def dangerous_comparison(self, left: Type, right: Type,
         if isinstance(left, UnionType) and isinstance(right, UnionType):
             left = remove_optional(left)
             right = remove_optional(right)
-        if (original_container and has_bytes_component(original_container) and
-                has_bytes_component(left)):
+        py2 = self.chk.options.python_version < (3, 0)
+        if (original_container and has_bytes_component(original_container, py2) and
+                has_bytes_component(left, py2)):
             # We need to special case bytes and bytearray, because 97 in b'abc', b'a' in b'abc',
             # b'a' in bytearray(b'abc') etc. all return True (and we want to show the error only
             # if the check can _never_ be True).
@@ -4179,13 +4180,16 @@ def custom_equality_method(typ: Type) -> bool:
     return False
 
 
-def has_bytes_component(typ: Type) -> bool:
+def has_bytes_component(typ: Type, py2: bool = False) -> bool:
     """Is this one of builtin byte types, or a union that contains it?"""
     typ = get_proper_type(typ)
+    if py2:
+        byte_types = {'builtins.str', 'builtins.bytearray'}
+    else:
+        byte_types = {'builtins.bytes', 'builtins.bytearray'}
     if isinstance(typ, UnionType):
         return any(has_bytes_component(t) for t in typ.items)
-    if isinstance(typ, Instance) and typ.type.fullname() in {'builtins.bytes',
-                                                             'builtins.bytearray'}:
+    if isinstance(typ, Instance) and typ.type.fullname() in byte_types:
         return True
     return False
 

test-data/unit/check-expressions.test

@@ -2066,6 +2066,12 @@ bytearray(b'abc') in b'abcde'  # OK on Python 3
 [builtins fixtures/primitives.pyi]
 [typing fixtures/typing-full.pyi]
 
+[case testBytesVsByteArray_python2]
+# flags: --strict-equality --py2
+b'hi' in bytearray(b'hi')
+[builtins_py2 fixtures/python2.pyi]
+[typing fixtures/typing-full.pyi]
+
 [case testStrictEqualityNoPromotePy3]
 # flags: --strict-equality
 'a' == b'a'  # E: Non-overlapping equality check (left operand type: "Literal['a']", right operand type: "Literal[b'a']")

test-data/unit/fixtures/python2.pyi

@@ -1,4 +1,4 @@
-from typing import Generic, Iterable, TypeVar
+from typing import Generic, Iterable, TypeVar, Sequence, Iterator
 
 class object:
     def __init__(self) -> None: pass
@@ -13,9 +13,16 @@ class function: pass
 class int: pass
 class str: pass
 class unicode: pass
-class bool: pass
+class bool(int): pass
+class bytearray(Sequence[int]):
+    def __init__(self, string: str) -> None: pass
+    def __contains__(self, item: object) -> bool: pass
+    def __iter__(self) -> Iterator[int]: pass
+    def __getitem__(self, item: int) -> int: pass
 
 T = TypeVar('T')
-class list(Iterable[T], Generic[T]): pass
+class list(Iterable[T], Generic[T]):
+    def __iter__(self) -> Iterator[T]: pass
+    def __getitem__(self, item: int) -> T: pass
 
 # Definition of None is implicit