Merge pull request #764 from SciML/s/new-build_function

WIP: build_function rewrite

Author: shashi

Project.toml

@@ -52,13 +52,13 @@ NaNMath = "0.3"
 RecursiveArrayTools = "2.3"
 Reexport = "0.2, 1"
 Requires = "1.0"
-RuntimeGeneratedFunctions = "0.4, 0.5"
+RuntimeGeneratedFunctions = "0.4.3, 0.5"
 SafeTestsets = "0.0.1"
 SciMLBase = "1.3"
 Setfield = "0.7"
 SpecialFunctions = "0.7, 0.8, 0.9, 0.10, 1.0"
 StaticArrays = "0.10, 0.11, 0.12, 1.0"
-SymbolicUtils = "0.7.4, 0.8"
+SymbolicUtils = "0.8"
 TreeViews = "0.3"
 UnPack = "0.1, 1.0"
 Unitful = "1.1"

src/ModelingToolkit.jl

@@ -29,6 +29,8 @@ import SymbolicUtils: Term, Add, Mul, Pow, Sym, FnType,
                       @rule, Rewriters, substitute, similarterm,
                       promote_symtype
 
+import SymbolicUtils.Code: toexpr
+
 import SymbolicUtils.Rewriters: Chain, Postwalk, Prewalk, Fixpoint
 import DiffEqBase: @add_kwonly
 using LinearAlgebra: LU, BlasInt