Issue with sequence of non-erased type

[giacomociti]

Description

I'm struggling to create a non-erased type with a member returning a sequence of another (or even the same) non-erased type

Repro steps

[<TypeProvider>]
type BasicGenerativeProvider (config : TypeProviderConfig) as this =
	inherit TypeProviderForNamespaces (config, assemblyReplacementMap=[("LemonadeProvider.DesignTime", "LemonadeProvider.Runtime")])

	let ns = "LemonadeProvider"
	let asm = Assembly.GetExecutingAssembly()

	let createType typeName (count:int) =
		let asm = ProvidedAssembly()
		let myType = ProvidedTypeDefinition(asm, ns, typeName, Some typeof<obj>, isErased=false)

		let ctor = ProvidedConstructor([], invokeCode = fun _ -> <@@ () @@>)
		myType.AddMember(ctor)
		
		let resultType = ProvidedTypeBuilder.MakeGenericType(typedefof<seq<_>>, [myType])
		let lambda = Expr.Lambda(Var("_", typeof<int>), Expr.NewObject(ctor, []))
		let runtimeMethod = 
			let methodInfo = 
				match <@@ CommandRuntime.Map(id, []) @@> with
				| Patterns.Call(_, m, _) -> m
				| _ -> failwith "unexpected"
			ProvidedTypeBuilder.MakeGenericMethod(methodInfo.GetGenericMethodDefinition(), [myType])
		let integerSequence = <@@ Seq.init count id @@>
		let myProp = ProvidedProperty("foo", resultType, getterCode = function _ -> Expr.Call(runtimeMethod, [lambda ; integerSequence]))
			   
		myType.AddMember myProp
		asm.AddTypes [ myType ]
		myType

	let myParamType = 
		let t = ProvidedTypeDefinition(asm, ns, "GenerativeProvider", Some typeof<obj>, isErased=false)
		t.DefineStaticParameters( [ProvidedStaticParameter("Count", typeof<int>)], fun typeName args -> createType typeName (unbox<int> args.[0]))
		t
	do
		this.AddNamespace(ns, [myParamType])

where in the runtime project I have the following helper method:

type CommandRuntime =
    static member Map(f, items: seq<int>) = Seq.map f items

Expected behavior

I expected the above code to create a working type provider:

type Gimme5 = LemonadeProvider.GenerativeProvider<5>

[<Test>]
let ``Can list`` () =
    let x: Gimme5 list = Gimme5().foo |> Seq.toList
    Assert.AreEqual(5, x.Length)

Actual behavior

The error raised is 'unexpected erased target ProvidedTypeDefinition' (thrown in ProvidedTypes.fs)

Known workarounds

It works adding a guard at line 8982:

FSharp.TypeProviders.SDK/src/ProvidedTypes.fs

Line 8982 in 1584152

if ptd.BelongsToTargetModel then failwithf "unexpected erased target ProvidedTypeDefinition '%O'" ptd

if ptd.IsErased && ptd.BelongsToTargetModel then failwithf "unexpected erased target ProvidedTypeDefinition '%O'" ptd

and a similar one at line 9269

FSharp.TypeProviders.SDK/src/ProvidedTypes.fs

Line 9269 in 1584152

if x.BelongsToTargetModel then failwithf "unexpected target type definition '%O'" x

 if x.IsErased && x.BelongsToTargetModel then failwithf "unexpected target type definition '%O'" x

but I'm a bit reluctant to propose such changes because I have no idea about their possible impacts.