Assertion failed: Struct fields can only be accessed with a pointer on the stack

[mmusu3]

Using ILSpy 4
Assertion fails when compiled in both Debug and Release.

Source:

class AssertTest
{
    struct DataStruct { }

    struct WrapperStruct
    {
        internal DataStruct Data;
    }

    class SomeClass
    {
        internal WrapperStruct DataWrapper;
    }

    SomeClass someClass;

    public void Test()
    {
        GetMember(() => someClass.DataWrapper.Data);
    }

    public static MemberInfo GetMember<T>(Expression<Func<T>> p) => default;
}

[cshung]

Hello maintainers, I am interested in fixing this bug.

[dgrunwald]

Great! I haven't looked at it in detail, but believe the bug here is in TransformExpressionTrees producing an invalid ILAst in this case.
If you haven't seen the ILAst yet, check out this comment.

You can decompile the equivalent function using a lambda instead of expression tree, to see how the ILAst should look in this situation.

[cshung]

Thanks for the idea, I will look into the ILAst of the lambda.

I think I have an idea about what gone wrong in TransformExpressionTrees , here is what I am thinking right now.

https://github.com/icsharpcode/ILSpy/compare/master...cshung:dev/andrewau/1224?expand=1