It doesn't take effect while using `ConflictsWith: []string{"acl.group_name"}` with nested block

Terraform Providers Azure
1

It doesn’t take effect and nothing is happened for “ConflictsWith” while using ConflictsWith: []string{"acl.group_name"} in nested block.

example:

"acl": {
    Type:     schema.TypeSet,
    Required: true,
    MinItems: 1,
    Elem: &schema.Resource{
        Schema: map[string]*schema.Schema{
            "user_name": {
                Type:          schema.TypeString,
                Optional:      true,
                ConflictsWith: []string{"acl.group_name"},
            },
            "group_name": {
                Type:          schema.TypeString,
                Optional:      true,
                ConflictsWith: []string{"acl.user_name"},
            },
            "permission": {
                Type:     schema.TypeString,
                Required: true,
            },
        },
    },
}