Can't emit Ldftn with symbolDocumentWriter

[odinmillion]

We are trying to emit Ldftn instruction. In some cases we see exception System.ArgumentException.

Look at this code:

public class Dummy
{
  public static int Add10(int x)
  {
    return x + 10;
  }
}

[TestFixture]
public class Tests
{
  [TestCase(true)]
  [TestCase(false)]
  public void TestLdftn(bool useDocumentWriter)
  {
    var id = $"asm-{Guid.NewGuid()}";
    var assembly = AppDomain.CurrentDomain.DefineDynamicAssembly(new AssemblyName(id), AssemblyBuilderAccess.RunAndCollect);
    var module = assembly.DefineDynamicModule(name: id, fileName: id + ".dll", emitSymbolInfo: true);
    var fooTypeBuilder = module.DefineType("Foo", TypeAttributes.Public | TypeAttributes.Class);
    var symWriter = module.GetSymWriter();
    var barMethod = fooTypeBuilder.DefineMethod("Bar", MethodAttributes.Public | MethodAttributes.Static, typeof(int), new[] { typeof(int) });
    var documentName = fooTypeBuilder.Name + "." + barMethod.Name + ".cil";
    var documentWriter = symWriter.DefineDocument(documentName, SymDocumentType.Text, SymLanguageType.ILAssembly, Guid.Empty);
    using (var il = useDocumentWriter
      ? new GroboIL(barMethod, documentWriter)
      : new GroboIL(barMethod))
    {
      il.Ldnull(); // stack: [null]
      il.Ldftn(typeof(Dummy).GetMethod("Add10")); // stack: [null, Add10*]
      il.Newobj(typeof(Func<int, int>).GetConstructor(new[] { typeof(object), typeof(IntPtr) })); // stack: [func]
      il.Ldc_I4(5); // stack: [func, 5]
      il.Call(typeof(Func<int, int>).GetMethod("Invoke")); // stack: [int]
      il.Ret();
    }
    var fooType = fooTypeBuilder.CreateType();

    var result = fooType.GetMethod("Bar").Invoke(null, new object[] { 5 });

    result.Should().Be(15);
  }
}

We can succesfully emit and run code without document writer. But we see that exception in opposite scenario:

System.ArgumentException : Не удается передать указанный код операции в метод EmitCall.
Имя параметра: opcode
   в System.Reflection.Emit.ILGenerator.EmitCall(OpCode opcode, MethodInfo methodInfo, Type[] optionalParameterTypes)
   в GrEmit.GroboIL.Emit(OpCode opCode, ILInstructionParameter parameter) в C:\BuildAgent\work\249acc80a2fd7042\GrEmit\GrEmit\GroboIL.cs:строка 2000
   в GrEmit.GroboIL.Dispose() в C:\BuildAgent\work\249acc80a2fd7042\GrEmit\GrEmit\GroboIL.cs:строка 147
   в GremitBugs.Tests.TestLdftn(Boolean useDocumentWriter) в C:\Users\****\Documents\Visual Studio 2017\Projects\GremitWeaks\GremitBugs\Tests.cs:строка 45

We assume that bug is located here:

gremit/GrEmit/GrEmit/GroboIL.cs

Lines 1999 to 2000 in b08a146

	else if(parameter is MethodILInstructionParameter)
	il.EmitCall(opCode, ((MethodILInstructionParameter)parameter).Method, null);

Sometimes MethodILInstructionParameter leads to emit non call opcodes :)