CI failures look like:

src/Compilers/Test/Utilities/VisualBasic/CompilationTestUtils.vb(1217,22): error BC30455: Argument not specified for parameter 'Number' of 'Public Function Str(Number As Object) As String'.

this makes it seem like the preview contains certain VB core methods that the stable does not, which is odd.

this makes it seem like the preview contains certain VB core methods that the stable does not, which is odd.

Actually it makes sense. I remember us having to make changes here because we found the assembly was wrong at some point.

@jaredpar does this mean that the assemblies in the "stable" version of these reference assemblies are wrong, and the ones in the earlier "preview" version are right?

@RikkiGibson

does this mean that the assemblies in the "stable" version of these reference assemblies are wrong, and the ones in the earlier "preview" version are right?

That matches my memories of this. I tracked down the point where we moved to this package and it's PR #29827.

@tmat may remember why we needed the non-RTM packages here. My vague memory is that this is still the time when we were dealing with the issues around MS.VB.dll being incomplete. It took a while to find all the places where the incomplete version was being published and fix it to have the complete one. This is likely another one of those cases

I'm dropping this work for now, assuming that the necessary workarounds are being pursued in #51647