Issues with redundant initial conditions in Buildings model?

[Francesco Casella]

Please check ​Buildings.Experimental.DistrictHeatingCooling.Validation.HeatingCoolingHotWaterSmall. The backend fails with

Warning: It was not possible to determine if the initialization problem is consistent, because of not evaluable parameters/start values during compile time: pla.coo.con.vol.dynBal.medium.p = pla.coo.con.vol.dynBal.p_start (pla.sinCoo.p = pla.coo.con.vol.dynBal.p_start)
Warning: It was not possible to determine if the initialization problem is consistent, because of not evaluable parameters/start values during compile time: pla.hea.eva.vol.dynBal.medium.p = pla.hea.eva.vol.dynBal.p_start (pla.sinHea.p = pla.hea.eva.vol.dynBal.p_start)
Notification: Performance of analyzeInitialSystem (initialization): time 0.195/7.507, allocations: 29.7 MB / 2.141 GB, free: 0.611 GB / 1.292 GB
Notification: Performance of solveInitialSystemEqSystem (initialization): time 9.535e-05/7.507, allocations: 24 kB / 2.141 GB, free: 0.611 GB / 1.292 GB
Error: Internal error IndexReduction.pantelidesIndexReduction failed! System is structurally singular and cannot be handled because the number of unassigned equations is larger than the number of states. Use -d=bltdump to get more information.
Error: No system for the symbolic initialization was generated

I guess the problem is that there initial equations made redundant by state constraints, and the backend can't deal with them because they are parameter-dependent.

In this case, I would suggest the backend to make those parameters structural and constant-evaluate them. I tried to do that by turning on the evaluate all parameters option, but unfortunately this doesn't work because the model uses external functions and the frontend cannot evaluate them.