I am trying to understand the concept of Class Inheritance in PowerShell. I almost get everything works, just need someone to explain the error and the empty constructor that I accidentally found out.

I define a base class.

class Human {
    [string]$name
    [string]$gender

    Human(){}  # Comment out this line and hit error
    Human($name, $gender)
    {
        $this.name = $name
        $this.gender = $gender
    }

    [void]Speak()
    {
        Write-Host -ForegroundColor Green "I am a human"
    }
}

Define Teacher class derived from Human class.

class Teacher : Human {
    # Don't need to repeat $name & $gender if inherit from Human class

    # Introduce new class property -> $subject
    [string]$subject

    Teacher($name, $gender, $subject)
    {
        $this.name = $name
        $this.gender = $gender
        $this.subject = $subject
    }

    # Overrides Speak() method in Human class
    [void]Speak()
    {
        Write-Host -ForegroundColor Green "I am a $($this.subject) teacher"
    }
}

$t1 = [Teacher]::new("Steven", 'Male', 'English')
$t1
$t1.Speak()

Instance $t1 works just fine with following output.

subject name   gender
------- ----   ------
English Steven Male

I am a English teacher

I will get following output with an error message if comment out the Human(){} in Human class. Though PowerShell still print output for $t1 and $t1.Speak(). For the record, I am using PowerShell 7.4.2 on VS Code. And here is my reference for class inheritance.

MethodException: 
Line |
   8 |      {
     |      ~
     | Cannot find an overload for "new" and the argument count: "0".