Solving Typing problems for Interfaces

Visual Basic 6 is an “unrestricted type”, which means types do not need to be declared; they can be solved during runtime.

The VBUC provides a Typer tool that tries to resolve the uses of the references in order to declare their types consistently as they were used originally. The same feature applies for interfaces too, although the complexity is higher because the Typer must take into account uses of the references in the interface and the implementing classes.

Original VB6 code

AnInterface.cls

Property Get varStr()
    varStr = ""
End Property
Sub foo(arg As Variant)
End Sub

AClass.cls

Implements AnInterface
Property Get AnInterface_varStr()
    AnInterface_varStr = ""
End Property
Sub AnInterface_foo(arg As Variant)
    arg = 0
End Sub

VBUC resulting VB.NET code

AnInterface.cls

Interface AnInterface
    ReadOnly Property varStr As String
    Sub foo(ByRef arg As Byte)
End Interface
Friend Class AnInterface_CoClass
    Implements AnInterface
    Public ReadOnly Property varStr() As String Implements AnInterface.varStr
        Get
            Return ""
        End Get
    End Property
    
    Public Sub foo(ByRef arg As Byte) Implements AnInterface.foo
    End Sub
End Class

AClass.cls

    Implements AnInterface
    ReadOnly Property AnInterface_varStr() As String Implements AnInterface.varStr
        Get
            Return ""
        End Get
    End Property
    Sub AnInterface_foo(ByRef arg As Byte) Implements AnInterface.foo
        arg = 0
    End Sub

VBUC resulting C#.NET code

AnInterface.cls

    interface AnInterface
    {
        string varStr{ get; } 
        void  foo(ref  byte arg);
    } 
    internal class AnInterface_CoClass
    : AnInterface
    {
        public string varStr
        {
            get
            {
                return "";
            }
        }
        public void  foo(ref  byte arg)
        {
        }
    }

AClass.cls

    internal class AClass
    : AnInterface
    {
        public string varStr
        {
            get
            {
                return "";
            }
        }
        public void  foo(ref  byte arg)
        {
            arg = 0;
        }
    }