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Bug: Double semicolon ;; between type definition and augmentation breaks operator overloading in FSI while it works with FSC
f#

Any of the The 3 double semicoloned lines between the MyVec definition and augmentation will cause
"error FS0001: The type 'MyVec<int>' does not support any operators named '+'" within FSI while it works with FSC

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type MyVec<'a> =
    { x : 'a; y : 'a }


;;              // Causes error
let test = ();; // Causes error
open System;;   // Causes error


type MyVec<'a> with
    static member (+) (l, r) =
        { x = l.x + r.x; y = l.x + r.y }
    static member TestStaticMember () = ()
    member x.TestMember () = ()


let a = { x = 2; y = 3 }


let b = a + a   //"error FS0001: The type 'MyVec<int>' does not support any operators named '+'"
let c = MyVec<int>.op_Addition (a, a)   // Good
MyVec<int>.TestStaticMember ()          // Good
let d = a.TestMember ()                 // Good
.

Yep, looks like a bug.

I tried it in VS 2010 (Beta 1), and got the same result.

By on 10/25/2009 9:53 PM ()

Adding the semicolons indicates that this code should be treated as two seperate "interactions" sent to the F# Interactive. For the most part, it does not matter whether code is sent as seperate interactions, or sent as one long interaction. However for extension members, it does matter - extension members sent as part of the same interaction where a type is defined are treated as part of the type. When sent as a seprate interaction, they are treated as true extension members.

In this particular case, this is combining with the fact that extension members are not used in finding operator overloads. That is - you cannot implement an operator overload for a type using an "extension operator". So when sent as seperate interactions, or as a single interaction with the ;; inserted, this code should fail because the operator is not defined on the type itself.

By on 10/26/2009 11:03 PM ()

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