Question

以下类型提供程序旨在创建GeneratedNamespace.MyType，它接受类型为string的静态参数，并且只包含一个空构造函数

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 
                    //(https://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 ()

当我尝试像这样使用它时

open System
open GeneratedNamespace
type X = MyType<"Abacaba">
[<EntryPoint>]
let main argv = 
    printfn "%A %A" typedefof<X> (new X())
    Console.ReadLine() |> ignore
    0

行type X = MyType<"Abacaba">产生错误

错误FS3039：直接引用生成的类型＆＃39; MyType＆＃39;不是允许的。

我添加了base constructor call，但它没有帮助

类型提供者是故意生成的

我的类型提供程序是否有错误？

Answer 1

我不确定如何让它完全正常工作，但我认为你得到错误的原因是参数化类型是一种擦除类型（而一旦静态参数返回的类型）提供的不是擦除类型）。

将IsErased = false添加到t会导致错误消失：

let  staticParams = [ProvidedStaticParameter("value",typedefof<string>)] 
let t = 
  ProvidedTypeDefinition
    (assembly,namespaceName,"MyType",Some typedefof<Object>,IsErased = false)
do t.DefineStaticParameters(staticParams,instantiationFunction)

有了这个，可以编译代码，但尝试使用new X()创建实例给出：

错误FS0192：内部错误：null：GetTRefType

所以，我可能还缺少其他东西。也许它可以指出你正确的方向！

错误FS3039：直接引用生成的类型＆＃39; MyType＆＃39;是不允许的

1 个答案: