Backend can't handle nested record assignment

[Per Östlund]

Many HelmHoltzMedia models (such as ​HelmholtzMedia.Examples.MediaTestModels.ButaneTestModel_dT) currently fail with error messages such as (using -d=newInst, the old frontend can't handle the models):

Warning: SimCodeUtil.makeSES_SIMPLE_ASSIGN failed for:
  Medium.ThermodynamicState(
    fixedMassFlowRate.medium.sat.liq.phase,
    fixedMassFlowRate.medium.sat.liq.T,
    fixedMassFlowRate.medium.sat.liq.p,
    fixedMassFlowRate.medium.sat.liq.d,
    fixedMassFlowRate.medium.sat.liq.u,
    fixedMassFlowRate.medium.sat.liq.h,
    fixedMassFlowRate.medium.sat.liq.s) =
  $TMP_Medium_SaturationProperties74.liq

This seems to be due to the flattened equation:

fixedMassFlowRate.medium.sat =
  HelmholtzMedia.Examples.MediaTestModels.ButaneTestModel_dT.Medium.setSat_p(fixedMassFlowRate.medium.p);

that the backend expands to:

Medium.SaturationProperties(
  fixedMassFlowRate.medium.sat.psat,
  fixedMassFlowRate.medium.sat.Tsat,
  Medium.ThermodynamicState(
    fixedMassFlowRate.medium.sat.liq.phase,
    fixedMassFlowRate.medium.sat.liq.T,
    fixedMassFlowRate.medium.sat.liq.p,
    fixedMassFlowRate.medium.sat.liq.d,
    fixedMassFlowRate.medium.sat.liq.u,
    fixedMassFlowRate.medium.sat.liq.h,
    fixedMassFlowRate.medium.sat.liq.s),
  Medium.ThermodynamicState(
    fixedMassFlowRate.medium.sat.vap.phase,
    fixedMassFlowRate.medium.sat.vap.T,
    fixedMassFlowRate.medium.sat.vap.p,
    fixedMassFlowRate.medium.sat.vap.d,
    fixedMassFlowRate.medium.sat.vap.u,
    fixedMassFlowRate.medium.sat.vap.h,
    fixedMassFlowRate.medium.sat.vap.s)) =
HelmholtzMedia.Examples.MediaTestModels.ButaneTestModel_dT.Medium.setSat_p(volume.medium.p)

But it seems like the case for Record() = f() in SimCodeUtil.createSingleComplexEqnCode2 can't handle the nested records and calls makeSES_SIMPLE_ASSIGN with a record as the lhs causing it to fail.

[matthis.thorade@…]

Since this commit
​https://github.com/OpenModelica/OpenModelica/commit/80ac1a491c0b0bc5c15e878636f0f0245295830d
most models are now compiling fine, and most also simulate, some fail during initialization:
​https://libraries.openmodelica.org/branches/newInst/HelmholtzMedia/HelmholtzMedia.html

[Francesco Casella]

I guess we can close this ticket.

Regarding the initialization issues, you may want to wait until #5770 is fixed.