Problem returning property that is using class for a class-based DSC resource

DscConfiguration.ps1

# For some attempts
using module SqlServerDsc

$ConfigurationData = @{
    AllNodes = @(
        @{
            NodeName = 'localhost'
            PSDscAllowDomainUser = $true 
            PSDSCAllowPlainTextPassword = $true
        }
    )
}

Configuration Example
{
    Import-DscResource -ModuleName 'SqlServerDsc'

    # For attempt 3
    $permisison1 = [DatabasePermission] @{
        State = 'Grant'
        Permission = @('Connect', 'Update')
    }

    node localhost
    {
        SimpleResource 'Grant-SQLTEST-sqluser'
        {
            Ensure       = 'Present'
            Name         = 'SQLTEST\sqluser'
            DatabaseName = 'AdventureWorks2'
            ServerName      = 'localhost'
            InstanceName    = 'sql2017'

            # Attempt 1 - throws compilation error
            <#
            Permission   = [CimInstance[]] @(
                (
                    New-CimInstance -ClientOnly -Namespace root/Microsoft/Windows/DesiredStateConfiguration -ClassName DatabasePermission -Property @{
                        State      = 'Grant'
                        Permission = @('Connect', 'Update')
                    }
                )
            )
            #>

            # Attempt 2 - throws compilation error
            
            <#
            Permission   = [DatabasePermission[]] @(
                [DatabasePermission] {
                    State      = 'Grant'
                    Permission = @('Connect', 'Update')
                }
            )
            #>

            # Attempt 3 - throws compilation error

            Permission   = [DatabasePermission[]] @(
                $permisison1
            )
        }
    }
}

Example -OutputPath c:\dsctemp -ConfigurationData $ConfigurationData

run.ps1

Invoke-DscResource -ModuleName <modulename> -Name SimpleResource -Method Get -Property @{
    Ensure               = 'Present'
    ServerName           = 'localhost'
    InstanceName         = 'sql2017'
    DatabaseName         = 'AdventureWorks2'
    Name                 = 'SQLTEST\sqluser'
    Permission           = [CimInstance[]] @(
        (
            New-CimInstance -ClientOnly -Namespace root/Microsoft/Windows/DesiredStateConfiguration -ClassName DatabasePermission -Property @{
                State = 'Grant'
                Permission = @('select')
            }
        )
        (
            New-CimInstance -ClientOnly -Namespace root/Microsoft/Windows/DesiredStateConfiguration -ClassName DatabasePermission -Property @{
                State = 'GrantWithGrant'
                Permission = @('update')
            }
        )
    )

SimpleResource.ps1

enum Ensure
{
    Present
    Absent
}

class Reason
{
    [DscProperty()]
    [System.String]
    $Code

    [DscProperty()]
    [System.String]
    $Phrase
}

class DatabasePermission
{
    [DscProperty(Key)]
    [ValidateSet('Grant', 'GrantWithGrant', 'Deny')]
    [System.String]
    $State

    [DscProperty(Mandatory)]
    [System.String[]]
    $Permission
}

[DscResource()]
class SimpleResource
{
    [DscProperty(Key)]
    [System.String]
    $InstanceName

    [DscProperty(Key)]
    [System.String]
    $DatabaseName

    [DscProperty(Key)]
    [System.String]
    $Name

    [DscProperty()]
    [System.String]
    $ServerName

    [DscProperty(Mandatory)]
    [DatabasePermission[]]
    $Permission

    [DscProperty()]
    [Ensure]
    $Ensure = [Ensure]::Present

    [DscProperty(NotConfigurable)]
    [Reason[]]
    $Reasons

    [SimpleResource] Get()
    {
        $dscResourceObject = [SimpleResource] @{
            InstanceName = 'SQL2017'
            DatabaseName = 'MyDB'
            Name = 'MyPrincipal'
            ServerName = 'MyHost'
            Ensure = 'Present'
            Permission = [DatabasePermission[]] @(
                    [DatabasePermission] @{
                        State = 'Grant'
                        Permission = @('CONNECT')
                    }
                    [DatabasePermission] @{
                        State = 'Deny'
                        Permission = @('SELECT')
                    }
                )
            Reasons = [Reason[]] @(
                [Reason] @{
                    Code = '{0}:{0}:Ensure' -f $this.GetType()
                    Phrase = 'The property Ensure should be Present, but was Absent'
                }
            )
        }
        
        return $dscResourceObject
    }

    [System.Boolean] Test()
    {
        return $true
    }

    [void] Set()
    {
    }
}