def map_type_from_supertype(typ: Type, sub_info: TypeInfo, super_info: TypeInfo) -> Type:
    """Map type variables in a type defined in a supertype context to be valid
    in the subtype context. Assume that the result is unique; if more than
    one type is possible, return one of the alternatives.

    For example, assume

    . class D(Generic[S]) ...
    . class C(D[E[T]], Generic[T]) ...

    Now S in the context of D would be mapped to E[T] in the context of C.
    """
    # Create the type of self in subtype, of form t[a1, ...].
    inst_type = self_type(sub_info)
    if isinstance(inst_type, TupleType):
        inst_type = inst_type.fallback
    # Map the type of self to supertype. This gets us a description of the
    # supertype type variables in terms of subtype variables, i.e. t[t1, ...]
    # so that any type variables in tN are to be interpreted in subtype
    # context.
    inst_type = map_instance_to_supertype(inst_type, super_info)
    # Finally expand the type variables in type with those in the previously
    # constructed type. Note that both type and inst_type may have type
    # variables, but in type they are interpreted in supertype context while
    # in inst_type they are interpreted in subtype context. This works even if
    # the names of type variables in supertype and subtype overlap.
    return expand_type_by_instance(typ, inst_type)

def map_type_from_supertype(typ, sub_info, super_info):
    """Map type variables in a type defined in a supertype context to be valid
    in the subtype context. Assume that the result is unique; if more than
    one type is possible, return one of the alternatives.
    
    For example, assume
    
      class D<S> ...
      class C<T> is D<E<T>> ...
    
    Now S in the context of D would be mapped to E<T> in the context of C.
    """
    # Create the type of self in subtype, of form t<a1, ...>.
    inst_type = self_type(sub_info)
    # Map the type of self to supertype. This gets us a description of the
    # supertype type variables in terms of subtype variables, i.e. t<t1, ...>
    # so that any type variables in tN are to be interpreted in subtype
    # context.
    inst_type = map_instance_to_supertype(inst_type, super_info)
    # Finally expand the type variables in type with those in the previously
    # constructed type. Note that both type and inst_type may have type
    # variables, but in type they are interpreterd in supertype context while
    # in inst_type they are interpreted in subtype context. This works even if
    # the names of type variables in supertype and subtype overlap.
    return expand_type_by_instance(typ, inst_type)

def analyse_member_var_access(name: str, itype: Instance, info: TypeInfo,
                              node: Context, is_lvalue: bool, is_super: bool,
                              msg: MessageBuilder,
                              report_type: Type = None) -> Type:
    """Analyse attribute access that does not target a method.

    This is logically part of analyse_member_access and the arguments are
    similar.
    """
    # It was not a method. Try looking up a variable.
    v = lookup_member_var_or_accessor(info, name, is_lvalue)

    vv = v
    if isinstance(vv, Decorator):
        # The associated Var node of a decorator contains the type.
        v = vv.var

    if isinstance(v, Var):
        # Found a member variable.
        var = v
        itype = map_instance_to_supertype(itype, var.info)
        if var.type:
            t = expand_type_by_instance(var.type, itype)
            if var.is_initialized_in_class and isinstance(t, FunctionLike):
                if is_lvalue:
                    if var.is_property:
                        msg.read_only_property(name, info, node)
                    else:
                        msg.cant_assign_to_method(node)

                if not var.is_staticmethod:
                    # Class-level function objects and classmethods become bound
                    # methods: the former to the instance, the latter to the
                    # class.
                    functype = cast(FunctionLike, t)
                    check_method_type(functype, itype, node, msg)
                    signature = method_type(functype)
                    if var.is_property:
                        # A property cannot have an overloaded type => the cast
                        # is fine.
                        return cast(Callable, signature).ret_type
                    else:
                        return signature
            return t
        else:
            if not var.is_ready:
                msg.cannot_determine_type(var.name(), node)
            # Implicit 'Any' type.
            return AnyType()
    elif isinstance(v, FuncDef):
        assert False, "Did not expect a function"

    # Could not find the member.
    if is_super:
        msg.undefined_in_superclass(name, node)
        return AnyType()
    else:
        return msg.has_no_attr(report_type or itype, name, node)

def instance_alias_type(alias: TypeAlias,
                        builtin_type: Callable[[str], Instance]) -> Type:
    """Type of a type alias node targeting an instance, when appears in runtime context.

    As usual, we first erase any unbound type variables to Any.
    """
    assert isinstance(alias.target, Instance), "Must be called only with aliases to classes"
    target = set_any_tvars(alias.target, alias.alias_tvars, alias.line, alias.column)
    assert isinstance(target, Instance)
    tp = type_object_type(target.type, builtin_type)
    return expand_type_by_instance(tp, target)

def analyze_member_var_access(name: str, itype: Instance, info: TypeInfo,
                              node: Context, is_lvalue: bool, is_super: bool,
                              builtin_type: Callable[[str], Instance],
                              not_ready_callback: Callable[[str, Context], None],
                              msg: MessageBuilder,
                              original_type: Type,
                              chk: 'mypy.checker.TypeChecker' = None) -> Type:
    """Analyse attribute access that does not target a method.

    This is logically part of analyze_member_access and the arguments are similar.

    original_type is the type of E in the expression E.var
    """
    # It was not a method. Try looking up a variable.
    v = lookup_member_var_or_accessor(info, name, is_lvalue)

    vv = v
    if isinstance(vv, Decorator):
        # The associated Var node of a decorator contains the type.
        v = vv.var

    if isinstance(v, Var):
        return analyze_var(name, v, itype, info, node, is_lvalue, msg,
                           original_type, not_ready_callback)
    elif isinstance(v, FuncDef):
        assert False, "Did not expect a function"
    elif not v and name not in ['__getattr__', '__setattr__', '__getattribute__']:
        if not is_lvalue:
            for method_name in ('__getattribute__', '__getattr__'):
                method = info.get_method(method_name)
                # __getattribute__ is defined on builtins.object and returns Any, so without
                # the guard this search will always find object.__getattribute__ and conclude
                # that the attribute exists
                if method and method.info.fullname() != 'builtins.object':
                    function = function_type(method, builtin_type('builtins.function'))
                    bound_method = bind_self(function, original_type)
                    typ = map_instance_to_supertype(itype, method.info)
                    getattr_type = expand_type_by_instance(bound_method, typ)
                    if isinstance(getattr_type, CallableType):
                        return getattr_type.ret_type

    if itype.type.fallback_to_any:
        return AnyType()

    # Could not find the member.
    if is_super:
        msg.undefined_in_superclass(name, node)
        return AnyType()
    else:
        if chk and chk.should_suppress_optional_error([itype]):
            return AnyType()
        return msg.has_no_attr(original_type, name, node)

def add_class_tvars(t: Type, itype: Instance, isuper: Optional[Instance], is_classmethod: bool,
                    builtin_type: Callable[[str], Instance],
                    original_type: Type) -> Type:
    """Instantiate type variables during analyze_class_attribute_access,
    e.g T and Q in the following:

    class A(Generic[T]):
        @classmethod
        def foo(cls: Type[Q]) -> Tuple[T, Q]: ...

    class B(A[str]): pass

    B.foo()

    original_type is the value of the type B in the expression B.foo()
    """
    # TODO: verify consistency between Q and T
    info = itype.type  # type: TypeInfo
    if is_classmethod:
        assert isuper is not None
        t = expand_type_by_instance(t, isuper)
    # We add class type variables if the class method is accessed on class object
    # without applied type arguments, this matches the behavior of __init__().
    # For example (continuing the example in docstring):
    #     A       # The type of callable is def [T] () -> A[T], _not_ def () -> A[Any]
    #     A[int]  # The type of callable is def () -> A[int]
    # and
    #     A.foo       # The type is generic def [T] () -> Tuple[T, A[T]]
    #     A[int].foo  # The type is non-generic def () -> Tuple[int, A[int]]
    #
    # This behaviour is useful for defining alternative constructors for generic classes.
    # To achieve such behaviour, we add the class type variables that are still free
    # (i.e. appear in the return type of the class object on which the method was accessed).
    free_ids = {t.id for t in itype.args if isinstance(t, TypeVarType)}

    if isinstance(t, CallableType):
        # NOTE: in practice either all or none of the variables are free, since
        # visit_type_application() will detect any type argument count mismatch and apply
        # a correct number of Anys.
        tvars = [TypeVarDef(n, n, i + 1, [], builtin_type('builtins.object'), tv.variance)
                 for (i, n), tv in zip(enumerate(info.type_vars), info.defn.type_vars)
                 # use 'is' to avoid id clashes with unrelated variables
                 if any(tv.id is id for id in free_ids)]
        if is_classmethod:
            t = bind_self(t, original_type, is_classmethod=True)
        return t.copy_modified(variables=tvars + t.variables)
    elif isinstance(t, Overloaded):
        return Overloaded([cast(CallableType, add_class_tvars(item, itype, isuper, is_classmethod,
                                                              builtin_type, original_type))
                           for item in t.items()])
    return t

def analyze_member_var_access(
    name: str,
    itype: Instance,
    info: TypeInfo,
    node: Context,
    is_lvalue: bool,
    is_super: bool,
    builtin_type: Callable[[str], Instance],
    not_ready_callback: Callable[[str, Context], None],
    msg: MessageBuilder,
    report_type: Type = None,
    chk: "mypy.checker.TypeChecker" = None,
) -> Type:
    """Analyse attribute access that does not target a method.

    This is logically part of analyze_member_access and the arguments are
    similar.
    """
    # It was not a method. Try looking up a variable.
    v = lookup_member_var_or_accessor(info, name, is_lvalue)

    vv = v
    if isinstance(vv, Decorator):
        # The associated Var node of a decorator contains the type.
        v = vv.var
    if isinstance(v, Var):
        return analyze_var(name, v, itype, info, node, is_lvalue, msg, not_ready_callback)
    elif isinstance(v, FuncDef):
        assert False, "Did not expect a function"
    elif not v and name not in ["__getattr__", "__setattr__"]:
        if not is_lvalue:
            method = info.get_method("__getattr__")
            if method:
                typ = map_instance_to_supertype(itype, method.info)
                getattr_type = expand_type_by_instance(
                    method_type_with_fallback(method, builtin_type("builtins.function")), typ
                )
                if isinstance(getattr_type, CallableType):
                    return getattr_type.ret_type

    if itype.type.fallback_to_any:
        return AnyType()

    # Could not find the member.
    if is_super:
        msg.undefined_in_superclass(name, node)
        return AnyType()
    else:
        if chk and chk.should_suppress_optional_error([itype]):
            return AnyType()
        return msg.has_no_attr(report_type or itype, name, node)

def analyze_var(
    name: str,
    var: Var,
    itype: Instance,
    info: TypeInfo,
    node: Context,
    is_lvalue: bool,
    msg: MessageBuilder,
    not_ready_callback: Callable[[str, Context], None],
) -> Type:
    """Analyze access to an attribute via a Var node.

    This is conceptually part of analyze_member_access and the arguments are similar.
    """
    # Found a member variable.
    itype = map_instance_to_supertype(itype, var.info)
    typ = var.type
    if typ:
        if isinstance(typ, PartialType):
            return handle_partial_attribute_type(typ, is_lvalue, msg, var)
        t = expand_type_by_instance(typ, itype)
        if is_lvalue and var.is_property and not var.is_settable_property:
            # TODO allow setting attributes in subclass (although it is probably an error)
            msg.read_only_property(name, info, node)
        if var.is_initialized_in_class and isinstance(t, FunctionLike):
            if is_lvalue:
                if var.is_property:
                    if not var.is_settable_property:
                        msg.read_only_property(name, info, node)
                else:
                    msg.cant_assign_to_method(node)

            if not var.is_staticmethod:
                # Class-level function objects and classmethods become bound
                # methods: the former to the instance, the latter to the
                # class.
                functype = t
                check_method_type(functype, itype, var.is_classmethod, node, msg)
                signature = method_type(functype)
                if var.is_property:
                    # A property cannot have an overloaded type => the cast
                    # is fine.
                    return cast(CallableType, signature).ret_type
                else:
                    return signature
        return t
    else:
        if not var.is_ready:
            not_ready_callback(var.name(), node)
        # Implicit 'Any' type.
        return AnyType()

def analyse_member_access(name, typ, node, is_lvalue, is_super, tuple_type, msg, override_info=None):
    """Analyse member access.

    This is a general operation that supports various different variations:
    
      1. lvalue or non-lvalue access (i.e. setter or getter access)
      2. supertype access (when using super(); is_super == True and
         override_info should refer to the supertype)
    """
    if isinstance(typ, Instance):
        if name == "__init__" and not is_super:
            # Accessing __init__ in statically typed code would compromise
            # type safety unless used via super().
            msg.fail(messages.CANNOT_ACCESS_INIT, node)
            return Any()

        # The base object has an instance type.
        itype = typ

        info = itype.type
        if override_info:
            info = override_info

        # Look up the member. First look up the method dictionary.
        method = None
        if not is_lvalue:
            method = info.get_method(name)

        if method:
            # Found a method. The call below has a unique result for all valid
            # programs.
            itype = map_instance_to_supertype(itype, method.info)
            return expand_type_by_instance(method_type(method), itype)
        else:
            # Not a method.
            return analyse_member_var_access(name, itype, info, node, is_lvalue, is_super, msg)
    elif isinstance(typ, Any):
        # The base object has dynamic type.
        return Any()
    elif isinstance(typ, TupleType):
        # Actually look up from the tuple type.
        return analyse_member_access(name, tuple_type, node, is_lvalue, is_super, tuple_type, msg)
    elif isinstance(typ, Callable) and (typ).is_type_obj():
        # Class attribute access.
        return msg.not_implemented("class attributes", node)
    else:
        # The base object has an unsupported type.
        return msg.has_no_member(typ, name, node)

def analyze_instance_member_access(name: str,
                                   typ: Instance,
                                   mx: MemberContext,
                                   override_info: Optional[TypeInfo]) -> Type:
    if name == '__init__' and not mx.is_super:
        # Accessing __init__ in statically typed code would compromise
        # type safety unless used via super().
        mx.msg.fail(message_registry.CANNOT_ACCESS_INIT, mx.context)
        return AnyType(TypeOfAny.from_error)

    # The base object has an instance type.

    info = typ.type
    if override_info:
        info = override_info

    if (state.find_occurrences and
            info.name() == state.find_occurrences[0] and
            name == state.find_occurrences[1]):
        mx.msg.note("Occurrence of '{}.{}'".format(*state.find_occurrences), mx.context)

    # Look up the member. First look up the method dictionary.
    method = info.get_method(name)
    if method:
        if method.is_property:
            assert isinstance(method, OverloadedFuncDef)
            first_item = cast(Decorator, method.items[0])
            return analyze_var(name, first_item.var, typ, info, mx)
        if mx.is_lvalue:
            mx.msg.cant_assign_to_method(mx.context)
        signature = function_type(method, mx.builtin_type('builtins.function'))
        signature = freshen_function_type_vars(signature)
        if name == '__new__':
            # __new__ is special and behaves like a static method -- don't strip
            # the first argument.
            pass
        else:
            signature = bind_self(signature, mx.original_type)
        typ = map_instance_to_supertype(typ, method.info)
        member_type = expand_type_by_instance(signature, typ)
        freeze_type_vars(member_type)
        return member_type
    else:
        # Not a method.
        return analyze_member_var_access(name, typ, info, mx)

def analyze_var(
    name: str, var: Var, itype: Instance, info: TypeInfo, node: Context, is_lvalue: bool, msg: MessageBuilder
) -> Type:
    """Analyze access to an attribute via a Var node.

    This is conceptually part of analyze_member_access and the arguments are similar.
    """
    # Found a member variable.
    itype = map_instance_to_supertype(itype, var.info)
    if var.type:
        t = expand_type_by_instance(var.type, itype)
        if var.is_initialized_in_class and isinstance(t, FunctionLike):
            if is_lvalue:
                if var.is_property:
                    if not var.is_settable_property:
                        msg.read_only_property(name, info, node)
                else:
                    msg.cant_assign_to_method(node)

            if not var.is_staticmethod:
                # Class-level function objects and classmethods become bound
                # methods: the former to the instance, the latter to the
                # class.
                functype = cast(FunctionLike, t)
                check_method_type(functype, itype, node, msg)
                signature = method_type(functype)
                if var.is_property:
                    # A property cannot have an overloaded type => the cast
                    # is fine.
                    return cast(CallableType, signature).ret_type
                else:
                    return signature
        return t
    else:
        if not var.is_ready:
            msg.cannot_determine_type(var.name(), node)
        # Implicit 'Any' type.
        return AnyType()

def analyse_member_var_access(name, itype, info, node, is_lvalue, is_super, msg):
    """Analyse member access that does not target a method.

    This is logically part of analyse_member_access and the arguments are
    similar.
    """
    # It was not a method. Try looking up a variable.
    v = lookup_member_var_or_accessor(info, name, is_lvalue)

    if isinstance(v, Var):
        # Found a member variable.
        var = v
        itype = map_instance_to_supertype(itype, var.info)
        if var.type:
            t = expand_type_by_instance(var.type, itype)
            if var.is_initialized_in_class and isinstance(t, FunctionLike):
                # Class-level function object becomes a bound method.
                functype = t
                check_method_type(functype, itype, node, msg)
                return method_type(functype)
            return t
        else:
            if not var.is_ready:
                msg.cannot_determine_type(var.name(), node)
            # Implicit 'any' type.
            return Any()
    elif isinstance(v, FuncDef):
        # Found a getter or a setter.
        raise NotImplementedError()

    # Could not find the member.
    if is_super:
        msg.undefined_in_superclass(name, node)
        return Any()
    else:
        return msg.has_no_member(itype, name, node)

def find_node_type(node: Union[Var, FuncBase], itype: Instance, subtype: Type) -> Type:
    """Find type of a variable or method 'node' (maybe also a decorated method).
    Apply type arguments from 'itype', and bind 'self' to 'subtype'.
    """
    from mypy.checkmember import bind_self
    if isinstance(node, FuncBase):
        typ = function_type(node,
                            fallback=Instance(itype.type.mro[-1], []))  # type: Optional[Type]
    else:
        typ = node.type
    if typ is None:
        return AnyType(TypeOfAny.from_error)
    # We don't need to bind 'self' for static methods, since there is no 'self'.
    if isinstance(node, FuncBase) or isinstance(typ, FunctionLike) and not node.is_staticmethod:
        assert isinstance(typ, FunctionLike)
        signature = bind_self(typ, subtype)
        if node.is_property:
            assert isinstance(signature, CallableType)
            typ = signature.ret_type
        else:
            typ = signature
    itype = map_instance_to_supertype(itype, node.info)
    typ = expand_type_by_instance(typ, itype)
    return typ

def analyze_member_var_access(name: str,
                              itype: Instance,
                              info: TypeInfo,
                              mx: MemberContext) -> Type:
    """Analyse attribute access that does not target a method.

    This is logically part of analyze_member_access and the arguments are similar.

    original_type is the type of E in the expression E.var
    """
    # It was not a method. Try looking up a variable.
    v = lookup_member_var_or_accessor(info, name, mx.is_lvalue)

    vv = v
    if isinstance(vv, Decorator):
        # The associated Var node of a decorator contains the type.
        v = vv.var

    if isinstance(vv, TypeInfo):
        # If the associated variable is a TypeInfo synthesize a Var node for
        # the purposes of type checking.  This enables us to type check things
        # like accessing class attributes on an inner class.
        v = Var(name, type=type_object_type(vv, mx.builtin_type))
        v.info = info

    if isinstance(vv, TypeAlias) and isinstance(vv.target, Instance):
        # Similar to the above TypeInfo case, we allow using
        # qualified type aliases in runtime context if it refers to an
        # instance type. For example:
        #     class C:
        #         A = List[int]
        #     x = C.A() <- this is OK
        typ = instance_alias_type(vv, mx.builtin_type)
        v = Var(name, type=typ)
        v.info = info

    if isinstance(v, Var):
        implicit = info[name].implicit

        # An assignment to final attribute is always an error,
        # independently of types.
        if mx.is_lvalue and not mx.chk.get_final_context():
            check_final_member(name, info, mx.msg, mx.context)

        return analyze_var(name, v, itype, info, mx, implicit=implicit)
    elif isinstance(v, FuncDef):
        assert False, "Did not expect a function"
    elif (not v and name not in ['__getattr__', '__setattr__', '__getattribute__'] and
          not mx.is_operator):
        if not mx.is_lvalue:
            for method_name in ('__getattribute__', '__getattr__'):
                method = info.get_method(method_name)
                # __getattribute__ is defined on builtins.object and returns Any, so without
                # the guard this search will always find object.__getattribute__ and conclude
                # that the attribute exists
                if method and method.info.fullname() != 'builtins.object':
                    function = function_type(method, mx.builtin_type('builtins.function'))
                    bound_method = bind_self(function, mx.original_type)
                    typ = map_instance_to_supertype(itype, method.info)
                    getattr_type = expand_type_by_instance(bound_method, typ)
                    if isinstance(getattr_type, CallableType):
                        result = getattr_type.ret_type

                        # Call the attribute hook before returning.
                        fullname = '{}.{}'.format(method.info.fullname(), name)
                        hook = mx.chk.plugin.get_attribute_hook(fullname)
                        if hook:
                            result = hook(AttributeContext(mx.original_type, result,
                                                           mx.context, mx.chk))
                        return result
        else:
            setattr_meth = info.get_method('__setattr__')
            if setattr_meth and setattr_meth.info.fullname() != 'builtins.object':
                setattr_func = function_type(setattr_meth, mx.builtin_type('builtins.function'))
                bound_type = bind_self(setattr_func, mx.original_type)
                typ = map_instance_to_supertype(itype, setattr_meth.info)
                setattr_type = expand_type_by_instance(bound_type, typ)
                if isinstance(setattr_type, CallableType) and len(setattr_type.arg_types) > 0:
                    return setattr_type.arg_types[-1]

    if itype.type.fallback_to_any:
        return AnyType(TypeOfAny.special_form)

    # Could not find the member.
    if mx.is_super:
        mx.msg.undefined_in_superclass(name, mx.context)
        return AnyType(TypeOfAny.from_error)
    else:
        if mx.chk and mx.chk.should_suppress_optional_error([itype]):
            return AnyType(TypeOfAny.from_error)
        return mx.msg.has_no_attr(mx.original_type, itype, name, mx.context)

def analyze_member_access(
    name: str,
    typ: Type,
    node: Context,
    is_lvalue: bool,
    is_super: bool,
    is_operator: bool,
    builtin_type: Callable[[str], Instance],
    not_ready_callback: Callable[[str, Context], None],
    msg: MessageBuilder,
    override_info: TypeInfo = None,
    report_type: Type = None,
    chk: "mypy.checker.TypeChecker" = None,
) -> Type:
    """Analyse attribute access.

    This is a general operation that supports various different variations:

      1. lvalue or non-lvalue access (i.e. setter or getter access)
      2. supertype access (when using super(); is_super == True and
         override_info should refer to the supertype)
    """
    report_type = report_type or typ
    if isinstance(typ, Instance):
        if name == "__init__" and not is_super:
            # Accessing __init__ in statically typed code would compromise
            # type safety unless used via super().
            msg.fail(messages.CANNOT_ACCESS_INIT, node)
            return AnyType()

        # The base object has an instance type.

        info = typ.type
        if override_info:
            info = override_info

        # Look up the member. First look up the method dictionary.
        method = info.get_method(name)
        if method:
            if method.is_property:
                assert isinstance(method, OverloadedFuncDef)
                return analyze_var(name, method.items[0].var, typ, info, node, is_lvalue, msg, not_ready_callback)
            if is_lvalue:
                msg.cant_assign_to_method(node)
            typ = map_instance_to_supertype(typ, method.info)
            if name == "__new__":
                # __new__ is special and behaves like a static method -- don't strip
                # the first argument.
                signature = function_type(method, builtin_type("builtins.function"))
            else:
                signature = method_type_with_fallback(method, builtin_type("builtins.function"))
            return expand_type_by_instance(signature, typ)
        else:
            # Not a method.
            return analyze_member_var_access(
                name,
                typ,
                info,
                node,
                is_lvalue,
                is_super,
                builtin_type,
                not_ready_callback,
                msg,
                report_type=report_type,
                chk=chk,
            )
    elif isinstance(typ, AnyType):
        # The base object has dynamic type.
        return AnyType()
    elif isinstance(typ, NoneTyp):
        if chk and chk.should_suppress_optional_error([typ]):
            return AnyType()
        # The only attribute NoneType has are those it inherits from object
        return analyze_member_access(
            name,
            builtin_type("builtins.object"),
            node,
            is_lvalue,
            is_super,
            is_operator,
            builtin_type,
            not_ready_callback,
            msg,
            report_type=report_type,
            chk=chk,
        )
    elif isinstance(typ, UnionType):
        # The base object has dynamic type.
        msg.disable_type_names += 1
        results = [
            analyze_member_access(
                name, subtype, node, is_lvalue, is_super, is_operator, builtin_type, not_ready_callback, msg, chk=chk
            )
            for subtype in typ.items
        ]
        msg.disable_type_names -= 1
        return UnionType.make_simplified_union(results)
    elif isinstance(typ, TupleType):
        # Actually look up from the fallback instance type.
#.........这里部分代码省略.........

def analyse_member_access(name: str, typ: Type, node: Context, is_lvalue: bool,
                          is_super: bool,
                          builtin_type: Function[[str], Instance],
                          msg: MessageBuilder, override_info: TypeInfo = None,
                          report_type: Type = None) -> Type:
    """Analyse attribute access.

    This is a general operation that supports various different variations:

      1. lvalue or non-lvalue access (i.e. setter or getter access)
      2. supertype access (when using super(); is_super == True and
         override_info should refer to the supertype)
    """
    report_type = report_type or typ
    if isinstance(typ, Instance):
        if name == '__init__' and not is_super:
            # Accessing __init__ in statically typed code would compromise
            # type safety unless used via super().
            msg.fail(messages.CANNOT_ACCESS_INIT, node)
            return AnyType()

        # The base object has an instance type.

        info = typ.type
        if override_info:
            info = override_info

        # Look up the member. First look up the method dictionary.
        method = info.get_method(name)
        if method:
            if is_lvalue:
                msg.cant_assign_to_method(node)
            typ = map_instance_to_supertype(typ, method.info)
            return expand_type_by_instance(
                method_type(method, builtin_type('builtins.function')), typ)
        else:
            # Not a method.
            return analyse_member_var_access(name, typ, info, node,
                                             is_lvalue, is_super, msg,
                                             report_type=report_type)
    elif isinstance(typ, AnyType):
        # The base object has dynamic type.
        return AnyType()
    elif isinstance(typ, UnionType):
        # The base object has dynamic type.
        msg.disable_type_names += 1
        results = [analyse_member_access(name, subtype, node, is_lvalue,
                                         is_super, builtin_type, msg)
                   for subtype in typ.items]
        msg.disable_type_names -= 1
        return UnionType.make_simplified_union(results)
    elif isinstance(typ, TupleType):
        # Actually look up from the fallback instance type.
        return analyse_member_access(name, typ.fallback, node, is_lvalue,
                                     is_super, builtin_type, msg)
    elif (isinstance(typ, FunctionLike) and
          cast(FunctionLike, typ).is_type_obj()):
        # Class attribute.
        # TODO super?
        sig = cast(FunctionLike, typ)
        itype = cast(Instance, sig.items()[0].ret_type)
        result = analyse_class_attribute_access(itype, name, node, is_lvalue, builtin_type, msg)
        if result:
            return result
        # Look up from the 'type' type.
        return analyse_member_access(name, sig.fallback, node, is_lvalue, is_super,
                                     builtin_type, msg, report_type=report_type)
    elif isinstance(typ, FunctionLike):
        # Look up from the 'function' type.
        return analyse_member_access(name, typ.fallback, node, is_lvalue, is_super,
                                     builtin_type, msg, report_type=report_type)
    return msg.has_no_attr(report_type, name, node)

def analyze_class_attribute_access(itype: Instance,
                                   name: str,
                                   mx: MemberContext) -> Optional[Type]:
    """original_type is the type of E in the expression E.var"""
    node = itype.type.get(name)
    if not node:
        if itype.type.fallback_to_any:
            return AnyType(TypeOfAny.special_form)
        return None

    is_decorated = isinstance(node.node, Decorator)
    is_method = is_decorated or isinstance(node.node, FuncBase)
    if mx.is_lvalue:
        if is_method:
            mx.msg.cant_assign_to_method(mx.context)
        if isinstance(node.node, TypeInfo):
            mx.msg.fail(message_registry.CANNOT_ASSIGN_TO_TYPE, mx.context)

    # If a final attribute was declared on `self` in `__init__`, then it
    # can't be accessed on the class object.
    if node.implicit and isinstance(node.node, Var) and node.node.is_final:
        mx.msg.fail(message_registry.CANNOT_ACCESS_FINAL_INSTANCE_ATTR
                    .format(node.node.name()), mx.context)

    # An assignment to final attribute on class object is also always an error,
    # independently of types.
    if mx.is_lvalue and not mx.chk.get_final_context():
        check_final_member(name, itype.type, mx.msg, mx.context)

    if itype.type.is_enum and not (mx.is_lvalue or is_decorated or is_method):
        return itype

    t = node.type
    if t:
        if isinstance(t, PartialType):
            symnode = node.node
            assert isinstance(symnode, Var)
            return mx.chk.handle_partial_var_type(t, mx.is_lvalue, symnode, mx.context)

        # Find the class where method/variable was defined.
        if isinstance(node.node, Decorator):
            super_info = node.node.var.info  # type: Optional[TypeInfo]
        elif isinstance(node.node, (Var, SYMBOL_FUNCBASE_TYPES)):
            super_info = node.node.info
        else:
            super_info = None

        # Map the type to how it would look as a defining class. For example:
        #     class C(Generic[T]): ...
        #     class D(C[Tuple[T, S]]): ...
        #     D[int, str].method()
        # Here itype is D[int, str], isuper is C[Tuple[int, str]].
        if not super_info:
            isuper = None
        else:
            isuper = map_instance_to_supertype(itype, super_info)

        if isinstance(node.node, Var):
            assert isuper is not None
            # Check if original variable type has type variables. For example:
            #     class C(Generic[T]):
            #         x: T
            #     C.x  # Error, ambiguous access
            #     C[int].x  # Also an error, since C[int] is same as C at runtime
            if isinstance(t, TypeVarType) or get_type_vars(t):
                # Exception: access on Type[...], including first argument of class methods is OK.
                if not isinstance(mx.original_type, TypeType):
                    mx.msg.fail(message_registry.GENERIC_INSTANCE_VAR_CLASS_ACCESS, mx.context)

            # Erase non-mapped variables, but keep mapped ones, even if there is an error.
            # In the above example this means that we infer following types:
            #     C.x -> Any
            #     C[int].x -> int
            t = erase_typevars(expand_type_by_instance(t, isuper))

        is_classmethod = ((is_decorated and cast(Decorator, node.node).func.is_class)
                          or (isinstance(node.node, FuncBase) and node.node.is_class))
        result = add_class_tvars(t, itype, isuper, is_classmethod, mx.builtin_type,
                                 mx.original_type)
        if not mx.is_lvalue:
            result = analyze_descriptor_access(mx.original_type, result, mx.builtin_type,
                                               mx.msg, mx.context, chk=mx.chk)
        return result
    elif isinstance(node.node, Var):
        mx.not_ready_callback(name, mx.context)
        return AnyType(TypeOfAny.special_form)

    if isinstance(node.node, TypeVarExpr):
        mx.msg.fail(message_registry.CANNOT_USE_TYPEVAR_AS_EXPRESSION.format(
                    itype.type.name(), name), mx.context)
        return AnyType(TypeOfAny.from_error)

    if isinstance(node.node, TypeInfo):
        return type_object_type(node.node, mx.builtin_type)

    if isinstance(node.node, MypyFile):
        # Reference to a module object.
        return mx.builtin_type('types.ModuleType')

    if isinstance(node.node, TypeAlias) and isinstance(node.node.target, Instance):
#.........这里部分代码省略.........

def analyze_var(name: str,
                var: Var,
                itype: Instance,