Template parameter deduction and with overloaded methods.

Hi All,

I have an overloaded generic method anmed "Foo":

Class Test
Class Xox(Of T)
End Class
Class Lulli(Of T)
Inherits Xox(Of T)
End Class

Overloads Shared Function Foo(Of T, Iter As Xox(Of T))(ByVal x As
Iter, ByVal tt As T) As Iter
Return x
End Function
Overloads Shared Function Foo(Of T)(ByVal l As Lulli(Of T), ByVal
tt As T) As Lulli(Of T)
Return l
End Function
Shared Sub Main()
Dim xox As New Xox(Of Integer)
Dim lulli As New Lulli(Of Integer)

Dim xx As Xox(Of Integer) = Foo(xox, 42)

' gives a BC30521 error
'Dim ll As Lulli(Of Integer) = Foo(lulli, 42)
End Sub
End Class

When I try to access the second overload, the compiler does not seem to
be able to find the correct method (BC30521). Explicitly declaring the
generic parameters solves the problem:

Dim ll As Lulli(Of Integer) = _
Foo(Of Integer, Lulli(Of Integer))(lulli, 42)

It look like the compiler can't deduct the generic arguments to find the
correct overload.

As this works from C#, I'm asking myself if this "as designed" or a bug
of the VB compiler?

TIA,
Andy

----
To email me directly, please remove the *NO*SPAM* parts below:
*NO*SPAM*xmen40@*NO*SPAM*gmx.net

Andreas,

"Andreas Mueller" <me@privacy.net> schrieb:
> I have an overloaded generic method anmed "Foo":
>
> Class Test
> Class Xox(Of T)
> End Class
> Class Lulli(Of T)
> Inherits Xox(Of T)
> End Class
>
> Overloads Shared Function Foo(Of T, Iter As Xox(Of T))(ByVal x As
> Iter, ByVal tt As T) As Iter
> Return x
> End Function
> Overloads Shared Function Foo(Of T)(ByVal l As Lulli(Of T), ByVal tt
> As T) As Lulli(Of T)
> Return l
> End Function
> Shared Sub Main()
> Dim xox As New Xox(Of Integer)
> Dim lulli As New Lulli(Of Integer)
>
> Dim xx As Xox(Of Integer) = Foo(xox, 42)
>
> ' gives a BC30521 error
> 'Dim ll As Lulli(Of Integer) = Foo(lulli, 42)
> End Sub
> End Class
>
> When I try to access the second overload, the compiler does not seem to be
> able to find the correct method (BC30521). Explicitly declaring the
> generic parameters solves the problem:
>
> Dim ll As Lulli(Of Integer) = _
> Foo(Of Integer, Lulli(Of Integer))(lulli, 42)
>
> It look like the compiler can't deduct the generic arguments to find the
> correct overload.
>
> As this works from C#, I'm asking myself if this "as designed" or a bug of
> the VB compiler?

I think this is a bug, because the chapter about overload resolution in the
language specification states that two methods with the same signature
due to type parameters should choose the less generic overload.

I suggest to file a bug report at
<URL:http://lab.msdn.microsoft.com/productfeedback/>. If you do not file
the bug in the next few days I'll submit a bug report on this issue.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

Herfried K. Wagner [MVP] wrote:

> Andreas,
>
> "Andreas Mueller" <me@privacy.net> schrieb:
>
>> I have an overloaded generic method anmed "Foo":
>>
>> Class Test
>> Class Xox(Of T)
>> End Class
>> Class Lulli(Of T)
>> Inherits Xox(Of T)
>> End Class
>>
>> Overloads Shared Function Foo(Of T, Iter As Xox(Of T))(ByVal x As
>> Iter, ByVal tt As T) As Iter
>> Return x
>> End Function
>> Overloads Shared Function Foo(Of T)(ByVal l As Lulli(Of T), ByVal
>> tt As T) As Lulli(Of T)
>> Return l
>> End Function
>> Shared Sub Main()
>> Dim xox As New Xox(Of Integer)
>> Dim lulli As New Lulli(Of Integer)
>>
>> Dim xx As Xox(Of Integer) = Foo(xox, 42)
>>
>> ' gives a BC30521 error
>> 'Dim ll As Lulli(Of Integer) = Foo(lulli, 42)
>> End Sub
>> End Class
>>
>> When I try to access the second overload, the compiler does not seem
>> to be able to find the correct method (BC30521). Explicitly declaring
>> the generic parameters solves the problem:
>>
>> Dim ll As Lulli(Of Integer) = _
>> Foo(Of Integer, Lulli(Of Integer))(lulli, 42)
>>
>> It look like the compiler can't deduct the generic arguments to find
>> the correct overload.
>>
>> As this works from C#, I'm asking myself if this "as designed" or a
>> bug of the VB compiler?
>
>
> I think this is a bug, because the chapter about overload resolution in
> the language specification states that two methods with the same signature
> due to type parameters should choose the less generic overload.
>
> I suggest to file a bug report at
> <URL:http://lab.msdn.microsoft.com/productfeedback/>. If you do not
> file the bug in the next few days I'll submit a bug report on this issue.
>
That's what I thought.
Logged it, DID FDBK42807
CU, Andy

--
To email me directly, please remove the *NO*SPAM* parts below:
*NO*SPAM*xmen40@*NO*SPAM*gmx.net

"Andreas Mueller" <me@privacy.net> schrieb:
> Logged it, DID FDBK42807

It seems that you have forgotten to upload the attachment.

<URL:http://lab.msdn.microsoft.com/productfeedback/viewfeedback.aspx?feedbackid=07751a75-a700-45b1-af3b-8751afcc7779>

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>

Herfried K. Wagner [MVP] wrote:

> "Andreas Mueller" <me@privacy.net> schrieb:
>
>> Logged it, DID FDBK42807
>
>
> It seems that you have forgotten to upload the attachment.
>
> <URL:http://lab.msdn.microsoft.com/productfeedback/viewfeedback.aspx?feedbackid=07751a75-a700-45b1-af3b-8751afcc7779>
>
>
ok, should be in now. looks like I just browsed for it and didn't hit
the attach button :-(

--
To email me directly, please remove the *NO*SPAM* parts below:
*NO*SPAM*xmen40@*NO*SPAM*gmx.net

Andreas,

"Andreas Mueller" <me@privacy.net> schrieb:
>>> Logged it, DID FDBK42807
>>
>> It seems that you have forgotten to upload the attachment.
>>
>> <URL:http://lab.msdn.microsoft.com/productfeedback/viewfeedback.aspx?feedbackid=07751a75-a700-45b1-af3b-8751afcc7779>
> ok, should be in now. looks like I just browsed for it and didn't hit the
> attach button :-(

Thanks very much. I have validated the bug and voted for it.

--
M S Herfried K. Wagner
M V P <URL:http://dotnet.mvps.org/>
V B <URL:http://classicvb.org/petition/>