Quotes and pattern matching in F #

Question

In a new console application, simply pasting the following code results in the exception "The parameter is not a recognized method name."

• Does the following code work on your installation?
• Joker: Do you know why it doesn't work on mine?

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// Learn more about F# at http://fsharp.net // See the 'F# Tutorial' project for more help. let somefunction1 arg = () let somefunction2 () = () open Quotations.DerivedPatterns let test() = let d = <@ somefunction1() @> let e = <@ somefunction2() @> match d with | SpecificCall <@ somefunction1() @> (a,b ,c) -> printfn "somefunction" | _ -> printfn "something else" match d with | SpecificCall <@ somefunction1 @> (a,b ,c) -> printfn "somefunction" | _ -> printfn "something else" match e with | SpecificCall <@ somefunction2() @> (a,b ,c) -> printfn "somefunction" | _ -> printfn "something else" //THIS FAILS HERE saying "The parameter is not a recognized method name" match e with | SpecificCall <@ somefunction2 @> (a,b ,c) -> printfn "somefunction" | _ -> printfn "something else" [<EntryPoint>] let main argv = test() printfn "%A" argv 0 // return an integer exit code 

Looking at the definition of the active SpecificCall template defined in the compiler, I find:

  [<CompiledName("SpecificCallPattern")>] let (|SpecificCall|_|) templateParameter = // Note: precomputation match templateParameter with | (Lambdas(_,Call(_,minfo1,_)) | Call(_,minfo1,_)) -> let isg1 = minfo1.IsGenericMethod let gmd = if isg1 then minfo1.GetGenericMethodDefinition() else null // end-of-precomputation (fun tm -> match tm with | Call(obj,minfo2,args) #if FX_NO_REFLECTION_METADATA_TOKENS when (minfo1.MethodHandle = minfo2.MethodHandle && #else when (minfo1.MetadataToken = minfo2.MetadataToken && #endif if isg1 then minfo2.IsGenericMethod && gmd = minfo2.GetGenericMethodDefinition() else minfo1 = minfo2) -> Some(obj,(minfo2.GetGenericArguments() |> Array.toList),args) | _ -> None) | _ -> invalidArg "templateParameter" (SR.GetString(SR.QunrecognizedMethodCall)) 

Answer 1

Offline, this looks good to me ... Is it possible that you somehow obscured the original definition of var ? For example, the following stand-alone example works fine for me:

 let var<'a>() = Unchecked.defaultof<'a> match <@ var<int>() @> with | Quotations.DerivedPatterns.SpecificCall <@ var @> (obj,_,[]) -> printfn "var" | _ -> printfn "something else"