Invalid custom attribute blob on FSharpList..ctor #15140
Description
The custom attribute blob on FSharpList..ctor is invalid:
.method assembly specialname rtspecialname
instance void .ctor() cil managed
{
.custom instance void System.Diagnostics.CodeAnalysis.DynamicDependencyAttribute::.ctor(valuetype System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes,
class [netstandard]System.Type) = ( 01 00 E0 07 00 00 2F 4D 69 63 72 6F 73 6F 66 74 // ....../Microsoft
2E 46 53 68 61 72 70 2E 43 6F 6C 6C 65 63 74 69 // .FSharp.Collecti
6F 6E 73 2E 46 53 68 61 72 70 4C 69 73 74 60 31 // ons.FSharpList`1
5B 5B 21 30 5D 5D 00 00 ) // [[!0]]..
.custom instance void [netstandard]System.Runtime.CompilerServices.CompilerGeneratedAttribute::.ctor() = ( 01 00 00 00 )
.custom instance void [netstandard]System.Diagnostics.DebuggerNonUserCodeAttribute::.ctor() = ( 01 00 00 00 )
// Code size 7 (0x7)
.maxstack 8
IL_0000: ldarg.0
IL_0001: call instance void [netstandard]System.Object::.ctor()
IL_0006: ret
} // end of method FSharpList`1::.ctor
Notice the FSharpList`1[[!0]] part. The intent of the !0 is to represent the first generic argument but that's not something the SerString format supports. See dotnet/runtime#4416 for a spec of the format.
Following C# program throws System.TypeLoadException: 'Could not load type '!0' from assembly 'FSharp.Core, Version=7.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a'.' (sorry, I have no clue how to write this in F#):
using System;
using System.Reflection;
using Microsoft.FSharp.Collections;
var attr = typeof(FSharpList<int>).GetConstructor(BindingFlags.NonPublic | BindingFlags.Instance, Type.EmptyTypes).GetCustomAttributes();
foreach (var a in attr)
Console.WriteLine(a);