[PL] TimeLoop: Remove generic setEquationSystem.

This is preparation for the PETSc nonlinear solver.
There we need different (from Picard) behaviour in
the Newton tag case.

ProcessLib/TimeLoop.cpp

@@ -21,30 +21,8 @@
 
 #include "CoupledSolutionsForStaggeredScheme.h"
 #include "ProcessData.h"
-
 namespace
 {
-//! Sets the EquationSystem for the given nonlinear solver,
-//! which is Picard or Newton depending on the NLTag.
-template <NumLib::NonlinearSolverTag NLTag>
-void setEquationSystem(NumLib::NonlinearSolverBase& nonlinear_solver,
-                       NumLib::EquationSystem& eq_sys,
-                       NumLib::ConvergenceCriterion& conv_crit)
-{
-    using Solver = NumLib::NonlinearSolver<NLTag>;
-    using EqSys = NumLib::NonlinearSystem<NLTag>;
-
-    assert(dynamic_cast<Solver*>(&nonlinear_solver) != nullptr);
-    assert(dynamic_cast<EqSys*>(&eq_sys) != nullptr);
-
-    auto& nl_solver_ = static_cast<Solver&>(nonlinear_solver);
-    auto& eq_sys_ = static_cast<EqSys&>(eq_sys);
-
-    nl_solver_.setEquationSystem(eq_sys_, conv_crit);
-}
-
-//! Sets the EquationSystem for the given nonlinear solver,
-//! transparently both for Picard and Newton solvers.
 void setEquationSystem(NumLib::NonlinearSolverBase& nonlinear_solver,
                        NumLib::EquationSystem& eq_sys,
                        NumLib::ConvergenceCriterion& conv_crit,
@@ -54,11 +32,42 @@ void setEquationSystem(NumLib::NonlinearSolverBase& nonlinear_solver,
     switch (nl_tag)
     {
         case Tag::Picard:
-            setEquationSystem<Tag::Picard>(nonlinear_solver, eq_sys, conv_crit);
+        {
+            using EqSys = NumLib::NonlinearSystem<Tag::Picard>;
+            auto& eq_sys_ = static_cast<EqSys&>(eq_sys);
+            if (auto* nl_solver =
+                    dynamic_cast<NumLib::NonlinearSolver<Tag::Picard>*>(
+                        &nonlinear_solver);
+                nl_solver != nullptr)
+            {
+                nl_solver->setEquationSystem(eq_sys_, conv_crit);
+            }
+            else
+            {
+                OGS_FATAL(
+                    "Could not cast nonlinear solver to Picard type solver.");
+            }
             break;
+        }
         case Tag::Newton:
-            setEquationSystem<Tag::Newton>(nonlinear_solver, eq_sys, conv_crit);
+        {
+            using EqSys = NumLib::NonlinearSystem<Tag::Newton>;
+            auto& eq_sys_ = static_cast<EqSys&>(eq_sys);
+
+            if (auto* nl_solver =
+                    dynamic_cast<NumLib::NonlinearSolver<Tag::Newton>*>(
+                        &nonlinear_solver);
+                nl_solver != nullptr)
+            {
+                nl_solver->setEquationSystem(eq_sys_, conv_crit);
+            }
+            else
+            {
+                OGS_FATAL(
+                    "Could not cast nonlinear solver to Newton type solver.");
+            }
             break;
+        }
     }
 }