feat: throw error when differentiating registered function with no derivative in structural_simplify

Author: AayushSabharwal

src/structural_transformation/StructuralTransformations.jl

@@ -4,6 +4,7 @@ using Setfield: @set!, @set
 using UnPack: @unpack
 
 using Symbolics: unwrap, linear_expansion, fast_substitute
+import Symbolics
 using SymbolicUtils
 using SymbolicUtils.Code
 using SymbolicUtils.Rewriters

src/structural_transformation/symbolics_tearing.jl

@@ -65,7 +65,7 @@ function eq_derivative!(ts::TearingState{ODESystem}, ieq::Int; kwargs...)
 
     sys = ts.sys
     eq = equations(ts)[ieq]
-    eq = 0 ~ ModelingToolkit.derivative(eq.rhs - eq.lhs, get_iv(sys))
+    eq = 0 ~ Symbolics.derivative(eq.rhs - eq.lhs, get_iv(sys); throw_no_derivative = true)
     push!(equations(ts), eq)
     # Analyze the new equation and update the graph/solvable_graph
     # First, copy the previous incidence and add the derivative terms.