The following type provider was intended to create GeneratedNamespace.MyType which accepts a static parameter of type string and contains only an empty constructor
namespace TypeProviderTest open Microsoft.FSharp.Core.CompilerServices open ProviderImplementation.ProvidedTypes open System.Reflection open System [<TypeProvider>] type MyTypeProvider(config:TypeProviderConfig) as this = inherit TypeProviderForNamespaces() let namespaceName="GeneratedNamespace" let assembly = Assembly.LoadFrom(config.RuntimeAssembly) //Provides definition, based on type parameters let instantiationFunction typeName (typeParams:obj[]) = match typeParams with | [|:? string as param|] -> //Creates an empty non-erased type let definition = ProvidedTypeDefinition( assembly, namespaceName, typeName, Some typedefof<Object>, IsErased = false ) //Creates an empty constructor let emptyCtor = ProvidedConstructor (parameters = []) //Provides a call to base constructor //(http://stackoverflow.com/questions/22520352/) //Doesn't seem to help let objCtor = typedefof<Object>.GetType().GetConstructor([||]) emptyCtor.BaseConstructorCall <- (fun _ -> objCtor,[]) emptyCtor.AddXmlDoc("Empty constructor test") definition.AddMember(emptyCtor) definition | _ -> failwith "That was not supported" let staticParams = [ProvidedStaticParameter("value",typedefof<string>)] let t = ProvidedTypeDefinition(assembly,namespaceName,"MyType",Some typedefof<Object>) do t.DefineStaticParameters(staticParams,instantiationFunction) do this.AddNamespace(namespaceName,[t]) [<assembly:TypeProviderAssembly>] do () When I try to use it like this
open System open GeneratedNamespace type X = MyType<"Abacaba"> [<EntryPoint>] let main argv = printfn "%A %A" typedefof<X> (new X()) Console.ReadLine() |> ignore 0 The line type X = MyType<"Abacaba"> produces the error
Error FS3039: A direct reference to the generated type 'MyType' is not permitted.
I added a base constructor call, but it didn't help
The type provider is made generative intentionally
Is there an error in my type provider?
1 Answers
Answers 1
I'm not sure how to make it fully work, but I think the reason why you're getting the error is that the parameterised type is an erased type (while the type that you return once static parameters are provided is not an erased type).
Adding IsErased = false to t makes the error go away:
let staticParams = [ProvidedStaticParameter("value",typedefof<string>)] let t = ProvidedTypeDefinition (assembly,namespaceName,"MyType",Some typedefof<Object>,IsErased = false) do t.DefineStaticParameters(staticParams,instantiationFunction) With this, the code can be compiled, but trying to create an instance using new X() gives:
error FS0192: internal error: null: GetTRefType
So, there is probably something else that I'm missing too. Perhaps it can point you into the right direction though!
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