Recent regression with NF

[massimo ceraolo]

The attached Netstart mdel simulated in 1.16-dev648 with both OF and NF.
With 1.17-dev141 does not work with NF. It issues the following message:

[1] 18:31:22 Translation Error
[C:/dev/OM64bit/OMCompiler/Compiler/NFFrontEnd/NFClassTree.mo: 609:13-609:91]: Internal error NFClassTree.ClassTree.instantiate got invalid class

[Per Östlund]

I guess you found the issue yourself, but now I'm curious what caused it :)

[massimo ceraolo]

One of my students when created model Netstart in DCDrive_pkg (I'm going to attach this as well) mistakenly used extend: the second row of the model.

When in the package, I did not see the red-box, so had no hint of the mistake.

When I posted the ticket, I extracted the error-creating model. Only later, when I loaded Netstart.mo by itself (i.e. without DCDrive_pck) I saw the red box, hinting from some missing dependency, and found the mistake.

It resulted that the OF is more tolerant with regard to that error than NF.

[Per Östlund]

I improved the error in ​#6973, now you'll instead get a more helpful error:

[DCDrive_pkg.mo:3:5-3:24:writable] Error: extends DCDrive_pkg causes an instantiation loop.

It's not technically an instantiation loop, as the OF shows, but it doesn't seem like something worth handling. But at least we can give an error that points to the issue rather than an unhelpful internal error.