Cause compiler error when Option Strict On : Option Explicit « Language Basics « VB.Net Tutorial

1. VB.Net Tutorial
2. Language Basics
3. Option Explicit

Module Module1
    
  Sub Main()

    Dim AnInt As Integer = 5
    Dim ALong As Long = 7

    ALong = AnInt
    'causes compiler error when Option Strict On
    'AnInt = ALong
    MsgBox(AnInt)

  End Sub

End Module