refactor: remove old clock handling code, retain error messages

Author: AayushSabharwal

src/systems/systemstructure.jl

@@ -634,53 +634,29 @@ end
 function structural_simplify!(state::TearingState, io = nothing; simplify = false,
         check_consistency = true, fully_determined = true, warn_initialize_determined = true,
         kwargs...)
-    if state.sys isa ODESystem
-        ci = ModelingToolkit.ClockInference(state)
-        ci = ModelingToolkit.infer_clocks!(ci)
-        time_domains = merge(Dict(state.fullvars .=> ci.var_domain),
-            Dict(default_toterm.(state.fullvars) .=> ci.var_domain))
-        tss, inputs, continuous_id, id_to_clock = ModelingToolkit.split_system(ci)
-        cont_io = merge_io(io, inputs[continuous_id])
-        sys, input_idxs = _structural_simplify!(tss[continuous_id], cont_io; simplify,
-            check_consistency, fully_determined,
-            kwargs...)
-        if length(tss) > 1
-            if continuous_id > 0
-                throw(HybridSystemNotSupportedException("Hybrid continuous-discrete systems are currently not supported with the standard MTK compiler. This system requires JuliaSimCompiler.jl, see https://help.juliahub.com/juliasimcompiler/stable/"))
-            end
-            # TODO: rename it to something else
-            discrete_subsystems = Vector{ODESystem}(undef, length(tss))
-            # Note that the appended_parameters must agree with
-            # `generate_discrete_affect`!
-            appended_parameters = parameters(sys)
-            for (i, state) in enumerate(tss)
-                if i == continuous_id
-                    discrete_subsystems[i] = sys
-                    continue
-                end
-                dist_io = merge_io(io, inputs[i])
-                ss, = _structural_simplify!(state, dist_io; simplify, check_consistency,
-                    fully_determined, kwargs...)
-                append!(appended_parameters, inputs[i], unknowns(ss))
-                discrete_subsystems[i] = ss
-            end
-            @set! sys.discrete_subsystems = discrete_subsystems, inputs, continuous_id,
-            id_to_clock
-            @set! sys.ps = appended_parameters
-            @set! sys.defaults = merge(ModelingToolkit.defaults(sys),
-                Dict(v => 0.0 for v in Iterators.flatten(inputs)))
+    ci = ModelingToolkit.ClockInference(state)
+    ci = ModelingToolkit.infer_clocks!(ci)
+    time_domains = merge(Dict(state.fullvars .=> ci.var_domain),
+        Dict(default_toterm.(state.fullvars) .=> ci.var_domain))
+    tss, inputs, continuous_id, id_to_clock = ModelingToolkit.split_system(ci)
+    if length(tss) > 1
+        if continuous_id == 0
+            throw(HybridSystemNotSupportedException("""
+            Discrete systems with multiple clocks are not supported with the standard \
+            MTK compiler.
+            """))
+        else
+            throw(HybridSystemNotSupportedException("""
+            Hybrid continuous-discrete systems are currently not supported with \
+            the standard MTK compiler. This system requires JuliaSimCompiler.jl, \
+            see https://help.juliahub.com/juliasimcompiler/stable/
+            """))
         end
-        ps = [sym isa CallWithMetadata ? sym :
-              setmetadata(
-                  sym, VariableTimeDomain, get(time_domains, sym, ContinuousClock()))
-              for sym in get_ps(sys)]
-        @set! sys.ps = ps
-    else
-        sys, input_idxs = _structural_simplify!(state, io; simplify, check_consistency,
-            fully_determined, kwargs...)
     end
-    has_io = io !== nothing
-    return has_io ? (sys, input_idxs) : sys
+
+    sys, input_idxs = _structural_simplify!(state, io; simplify, check_consistency,
+        fully_determined, kwargs...)
+    return io !== nothing ? (sys, input_idxs) : sys
 end
 
 function _structural_simplify!(state::TearingState, io; simplify = false,