Merge branch 'master' into for-loop-len-cache

Author: BobTheBuidler

README.md

@@ -142,6 +142,7 @@ Mypy can be integrated into popular IDEs:
 - Emacs: using [Flycheck](https://github.com/flycheck/)
 - Sublime Text: [SublimeLinter-contrib-mypy](https://github.com/fredcallaway/SublimeLinter-contrib-mypy)
 - PyCharm: [mypy plugin](https://github.com/dropbox/mypy-PyCharm-plugin)
+- IDLE: [idlemypyextension](https://github.com/CoolCat467/idlemypyextension)
 - pre-commit: use [pre-commit mirrors-mypy](https://github.com/pre-commit/mirrors-mypy), although
   note by default this will limit mypy's ability to analyse your third party dependencies.
 

docs/requirements-docs.txt

@@ -1,3 +1,4 @@
+-r ../mypy-requirements.txt
 sphinx>=8.1.0
 furo>=2022.3.4
 myst-parser>=4.0.0

docs/source/command_line.rst

@@ -728,9 +728,22 @@ of the above sections.
        if text != b'other bytes':  # Error: non-overlapping equality check!
            ...
 
-       assert text is not None  # OK, check against None is allowed as a special case.
+       assert text is not None  # OK, check against None is allowed
 
 
+.. option:: --strict-equality-for-none
+
+    This flag extends :option:`--strict-equality <mypy --strict-equality>` for checks
+    against ``None``:
+
+    .. code-block:: python
+
+       text: str
+       assert text is not None  # Error: non-overlapping identity check!
+
+    Note that :option:`--strict-equality-for-none <mypy --strict-equality-for-none>`
+    only works in combination with :option:`--strict-equality <mypy --strict-equality>`.
+
 .. option:: --strict-bytes
 
     By default, mypy treats ``bytearray`` and ``memoryview`` as subtypes of ``bytes`` which

docs/source/config_file.rst

@@ -834,7 +834,15 @@ section of the command line docs.
    :default: False
 
    Prohibit equality checks, identity checks, and container checks between
-   non-overlapping types.
+   non-overlapping types (except ``None``).
+
+.. confval:: strict_equality_for_none
+
+   :type: boolean
+   :default: False
+
+   Include ``None`` in strict equality checks (requires :confval:`strict_equality`
+   to be activated).
 
 .. confval:: strict_bytes
 

docs/source/error_code_list2.rst

@@ -145,6 +145,29 @@ literal:
     def is_magic(x: bytes) -> bool:
         return x == b'magic'  # OK
 
+:option:`--strict-equality <mypy --strict-equality>` does not include comparisons with
+``None``:
+
+.. code-block:: python
+
+    # mypy: strict-equality
+
+    def is_none(x: str) -> bool:
+        return x is None  # OK
+
+If you want such checks, you must also activate
+:option:`--strict-equality-for-none <mypy --strict-equality-for-none>` (we might merge
+these two options later).
+
+.. code-block:: python
+
+    # mypy: strict-equality strict-equality-for-none
+
+    def is_none(x: str) -> bool:
+        # Error: Non-overlapping identity check
+        #        (left operand type: "str", right operand type: "None")
+        return x is None
+
 .. _code-no-untyped-call:
 
 Check that no untyped functions are called [no-untyped-call]

mypy/cache.py

@@ -3,17 +3,21 @@
 from collections.abc import Sequence
 from typing import TYPE_CHECKING, Final
 
+from mypy_extensions import u8
+
 try:
     from native_internal import (
         Buffer as Buffer,
         read_bool as read_bool,
         read_float as read_float,
         read_int as read_int,
         read_str as read_str,
+        read_tag as read_tag,
         write_bool as write_bool,
         write_float as write_float,
         write_int as write_int,
         write_str as write_str,
+        write_tag as write_tag,
     )
 except ImportError:
     # TODO: temporary, remove this after we publish mypy-native on PyPI.
@@ -32,6 +36,12 @@ def read_int(data: Buffer) -> int:
         def write_int(data: Buffer, value: int) -> None:
             raise NotImplementedError
 
+        def read_tag(data: Buffer) -> u8:
+            raise NotImplementedError
+
+        def write_tag(data: Buffer, value: u8) -> None:
+            raise NotImplementedError
+
         def read_str(data: Buffer) -> str:
             raise NotImplementedError
 
@@ -51,45 +61,48 @@ def write_float(data: Buffer, value: float) -> None:
             raise NotImplementedError
 
 
-LITERAL_INT: Final = 1
-LITERAL_STR: Final = 2
-LITERAL_BOOL: Final = 3
-LITERAL_FLOAT: Final = 4
-LITERAL_COMPLEX: Final = 5
-LITERAL_NONE: Final = 6
+# Always use this type alias to refer to type tags.
+Tag = u8
+
+LITERAL_INT: Final[Tag] = 1
+LITERAL_STR: Final[Tag] = 2
+LITERAL_BOOL: Final[Tag] = 3
+LITERAL_FLOAT: Final[Tag] = 4
+LITERAL_COMPLEX: Final[Tag] = 5
+LITERAL_NONE: Final[Tag] = 6
 
 
-def read_literal(data: Buffer, marker: int) -> int | str | bool | float:
-    if marker == LITERAL_INT:
+def read_literal(data: Buffer, tag: Tag) -> int | str | bool | float:
+    if tag == LITERAL_INT:
         return read_int(data)
-    elif marker == LITERAL_STR:
+    elif tag == LITERAL_STR:
         return read_str(data)
-    elif marker == LITERAL_BOOL:
+    elif tag == LITERAL_BOOL:
         return read_bool(data)
-    elif marker == LITERAL_FLOAT:
+    elif tag == LITERAL_FLOAT:
         return read_float(data)
-    assert False, f"Unknown literal marker {marker}"
+    assert False, f"Unknown literal tag {tag}"
 
 
 def write_literal(data: Buffer, value: int | str | bool | float | complex | None) -> None:
     if isinstance(value, bool):
-        write_int(data, LITERAL_BOOL)
+        write_tag(data, LITERAL_BOOL)
         write_bool(data, value)
     elif isinstance(value, int):
-        write_int(data, LITERAL_INT)
+        write_tag(data, LITERAL_INT)
         write_int(data, value)
     elif isinstance(value, str):
-        write_int(data, LITERAL_STR)
+        write_tag(data, LITERAL_STR)
         write_str(data, value)
     elif isinstance(value, float):
-        write_int(data, LITERAL_FLOAT)
+        write_tag(data, LITERAL_FLOAT)
         write_float(data, value)
     elif isinstance(value, complex):
-        write_int(data, LITERAL_COMPLEX)
+        write_tag(data, LITERAL_COMPLEX)
         write_float(data, value.real)
         write_float(data, value.imag)
     else:
-        write_int(data, LITERAL_NONE)
+        write_tag(data, LITERAL_NONE)
 
 
 def read_int_opt(data: Buffer) -> int | None:

mypy/checker.py

@@ -5552,10 +5552,10 @@ def visit_continue_stmt(self, s: ContinueStmt) -> None:
         return
 
     def visit_match_stmt(self, s: MatchStmt) -> None:
-        named_subject = self._make_named_statement_for_match(s)
         # In sync with similar actions elsewhere, narrow the target if
         # we are matching an AssignmentExpr
         unwrapped_subject = collapse_walrus(s.subject)
+        named_subject = self._make_named_statement_for_match(s, unwrapped_subject)
         with self.binder.frame_context(can_skip=False, fall_through=0):
             subject_type = get_proper_type(self.expr_checker.accept(s.subject))
 
@@ -5646,9 +5646,8 @@ def visit_match_stmt(self, s: MatchStmt) -> None:
             with self.binder.frame_context(can_skip=False, fall_through=2):
                 pass
 
-    def _make_named_statement_for_match(self, s: MatchStmt) -> Expression:
+    def _make_named_statement_for_match(self, s: MatchStmt, subject: Expression) -> Expression:
         """Construct a fake NameExpr for inference if a match clause is complex."""
-        subject = s.subject
         if self.binder.can_put_directly(subject):
             # Already named - we should infer type of it as given
             return subject

mypy/checker_shared.py

@@ -272,6 +272,10 @@ def checking_await_set(self) -> Iterator[None]:
     def get_precise_awaitable_type(self, typ: Type, local_errors: ErrorWatcher) -> Type | None:
         raise NotImplementedError
 
+    @abstractmethod
+    def add_any_attribute_to_type(self, typ: Type, name: str) -> Type:
+        raise NotImplementedError
+
     @abstractmethod
     def is_defined_in_stub(self, typ: Instance, /) -> bool:
         raise NotImplementedError

mypy/checkexpr.py

@@ -3721,7 +3721,7 @@ def visit_comparison_expr(self, e: ComparisonExpr) -> Type:
             elif operator == "is" or operator == "is not":
                 right_type = self.accept(right)  # validate the right operand
                 sub_result = self.bool_type()
-                if self.dangerous_comparison(left_type, right_type):
+                if self.dangerous_comparison(left_type, right_type, identity_check=True):
                     # Show the most specific literal types possible
                     left_type = try_getting_literal(left_type)
                     right_type = try_getting_literal(right_type)
@@ -3763,6 +3763,7 @@ def dangerous_comparison(
         original_container: Type | None = None,
         seen_types: set[tuple[Type, Type]] | None = None,
         prefer_literal: bool = True,
+        identity_check: bool = False,
     ) -> bool:
         """Check for dangerous non-overlapping comparisons like 42 == 'no'.
 
@@ -3790,10 +3791,12 @@ def dangerous_comparison(
 
         left, right = get_proper_types((left, right))
 
-        # We suppress the error if there is a custom __eq__() method on either
-        # side. User defined (or even standard library) classes can define this
+        # We suppress the error for equality and container checks if there is a custom __eq__()
+        # method on either side. User defined (or even standard library) classes can define this
         # to return True for comparisons between non-overlapping types.
-        if custom_special_method(left, "__eq__") or custom_special_method(right, "__eq__"):
+        if (
+            custom_special_method(left, "__eq__") or custom_special_method(right, "__eq__")
+        ) and not identity_check:
             return False
 
         if prefer_literal:
@@ -3817,7 +3820,10 @@ def dangerous_comparison(
             #
             # TODO: find a way of disabling the check only for types resulted from the expansion.
             return False
-        if isinstance(left, NoneType) or isinstance(right, NoneType):
+        if self.chk.options.strict_equality_for_none:
+            if isinstance(left, NoneType) and isinstance(right, NoneType):
+                return False
+        elif isinstance(left, NoneType) or isinstance(right, NoneType):
             return False
         if isinstance(left, UnionType) and isinstance(right, UnionType):
             left = remove_optional(left)
@@ -6004,6 +6010,10 @@ def analyze_cond_branch(
     def _combined_context(self, ty: Type | None) -> Type | None:
         ctx_items = []
         if ty is not None:
+            if has_any_type(ty):
+                # HACK: Any should be contagious, `dict[str, Any] or <x>` should still
+                # infer Any in x.
+                return ty
             ctx_items.append(ty)
         if self.type_context and self.type_context[-1] is not None:
             ctx_items.append(self.type_context[-1])

mypy/checkpattern.py

@@ -671,12 +671,15 @@ def visit_class_pattern(self, o: ClassPattern) -> PatternType:
                 has_local_errors = local_errors.has_new_errors()
             if has_local_errors or key_type is None:
                 key_type = AnyType(TypeOfAny.from_error)
-                self.msg.fail(
-                    message_registry.CLASS_PATTERN_UNKNOWN_KEYWORD.format(
-                        typ.str_with_options(self.options), keyword
-                    ),
-                    pattern,
-                )
+                if not (type_info and type_info.fullname == "builtins.object"):
+                    self.msg.fail(
+                        message_registry.CLASS_PATTERN_UNKNOWN_KEYWORD.format(
+                            typ.str_with_options(self.options), keyword
+                        ),
+                        pattern,
+                    )
+                elif keyword is not None:
+                    new_type = self.chk.add_any_attribute_to_type(new_type, keyword)
 
             inner_type, inner_rest_type, inner_captures = self.accept(pattern, key_type)
             if is_uninhabited(inner_type):