Function analyze_class_attribute_access

mypy/checkmember.py:1135–1337

Analyze access to an attribute on a class object. itype is the return type of the class object callable, original_type is the type of E in the expression E.var, original_vars are type variables of the class callable (for generic classes).

(
    itype: Instance,
    name: str,
    mx: MemberContext,
    *,
    mcs_fallback: Instance,
    override_info: TypeInfo | None = None,
    original_vars: Sequence[TypeVarLikeType] | None = None,
)

def analyze_class_attribute_access(
    itype: Instance,
    name: str,
    mx: MemberContext,
    *,
    mcs_fallback: Instance,
    override_info: TypeInfo | None = None,
    original_vars: Sequence[TypeVarLikeType] | None = None,
) -> Type | None:
    """Analyze access to an attribute on a class object.

    itype is the return type of the class object callable, original_type is the type
    of E in the expression E.var, original_vars are type variables of the class callable
    (for generic classes).
    """
    info = itype.type
    if override_info:
        info = override_info

    fullname = f"{info.fullname}.{name}"
    hook = mx.chk.plugin.get_class_attribute_hook(fullname)

    node = info.get(name)
    if not node:
        if itype.extra_attrs and name in itype.extra_attrs.attrs:
            # For modules use direct symbol table lookup.
            if not itype.extra_attrs.mod_name:
                return itype.extra_attrs.attrs[name]
        if info.fallback_to_any or info.meta_fallback_to_any:
            return apply_class_attr_hook(mx, hook, AnyType(TypeOfAny.special_form))
        return None

    if (
        isinstance(node.node, Var)
        and not node.node.is_classvar
        and not hook
        and mcs_fallback.type.get(name)
    ):
        # If the same attribute is declared on the metaclass and the class but with different types,
        # and the attribute on the class is not a ClassVar,
        # the type of the attribute on the metaclass should take priority
        # over the type of the attribute on the class,
        # when the attribute is being accessed from the class object itself.
        #
        # Return `None` here to signify that the name should be looked up
        # on the class object itself rather than the instance.
        return None

    mx.chk.warn_deprecated(node.node, mx.context)

    is_decorated = isinstance(node.node, Decorator)
    is_method = is_decorated or isinstance(node.node, FuncBase)
    if mx.is_lvalue and not mx.suppress_errors:
        if is_method:
            mx.msg.cant_assign_to_method(mx.context)
        if isinstance(node.node, TypeInfo):
            mx.fail(message_registry.CANNOT_ASSIGN_TO_TYPE)