How to call a function from a call quote in a type provider?

Question

I have a type provider that gives me the error "Type mismatch when splicing an expression in literal quotation."

I extracted the code below to reproduce the problem in a smaller context.

let f (s : string) : string = s //some dummy implementation

let t = ProvidedTypeDefinition(asm, ns, "Root", Some typeof<obj>)
let ctor = ProvidedConstructor(parameters = [],
                               InvokeCode = (fun args -> <@@ "root" :> obj @@>)) :> MemberInfo

let prop = ProvidedProperty(propertyName = "SomeProperty",
                            parameters = [],
                            propertyType = typeof<string>,
                            GetterCode = (fun args -> <@@ f %%(args.[0]) @@>)) :> MemberInfo

do  t.AddMembers [ctor; prop]
    t.SetBaseType typeof<obj>

... and when I use a type provider like

let root = Provided.Root()

let a = root.SomeProperty

I get an error message:

Error: a provider of type 'typeproviders.providerpoc + MyProvider' reported an error in the context of the provided type 'typeproviders.providerpoc.Provided.Root', member of 'get_Menu'.

Error: the type of inconsistency when matching the expression in the quote is literal.

The type of the inserted expression tree does not match the type expected as a result of the splice operation.

Expected "System.Object", but got the type "System.String".

- , , (%% x: string) (% x: string).. : receivedType.

, ?

!

Answer 1

, , obj , string.

, GetterCode :

GetterCode = (fun args -> <@@ f %%(args.[0]) @@>)

args - , obj, f , , %%, string >

, obj string, :

GetterCode = (fun args -> <@@ f (unbox<string> (%%(args.[0]))) @@>)