Fix import of SymbolicUtils.jl on old julia

Author: MilesCranmer

Project.toml

@@ -16,12 +16,6 @@ Requires = "ae029012-a4dd-5104-9daa-d747884805df"
 TOML = "fa267f1f-6049-4f14-aa54-33bafae1ed76"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
-[weakdeps]
-SymbolicUtils = "d1185830-fcd6-423d-90d6-eec64667417b"
-
-[extensions]
-DynamicExpressionsSymbolicUtilsExt = "SymbolicUtils"
-
 [compat]
 Compat = "3.37, 4"
 LoopVectorization = "0.12"
@@ -33,6 +27,9 @@ SymbolicUtils = "0.19, ^1.0.5"
 Zygote = "0.6"
 julia = "1.6"
 
+[extensions]
+DynamicExpressionsSymbolicUtilsExt = "SymbolicUtils"
+
 [extras]
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
@@ -43,3 +40,6 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
 test = ["Test", "SafeTestsets", "SpecialFunctions", "ForwardDiff", "StaticArrays", "SymbolicUtils"]
+
+[weakdeps]
+SymbolicUtils = "d1185830-fcd6-423d-90d6-eec64667417b"

ext/DynamicExpressionsSymbolicUtilsExt.jl

@@ -3,13 +3,14 @@ module DynamicExpressionsSymbolicUtilsExt
 export node_to_symbolic, symbolic_to_node
 
 import Base: convert
-using SymbolicUtils
 if isdefined(Base, :get_extension)
+    using SymbolicUtils
     import DynamicExpressions.EquationModule: Node, DEFAULT_NODE_TYPE
     import DynamicExpressions.OperatorEnumModule: AbstractOperatorEnum
     import DynamicExpressions.UtilsModule: isgood, isbad, @return_on_false
     import DynamicExpressions.ExtensionInterfaceModule: node_to_symbolic, symbolic_to_node
 else
+    using ..SymbolicUtils
     import ..DynamicExpressions.EquationModule: Node, DEFAULT_NODE_TYPE
     import ..DynamicExpressions.OperatorEnumModule: AbstractOperatorEnum
     import ..DynamicExpressions.UtilsModule: isgood, isbad, @return_on_false

src/ExtensionInterface.jl

@@ -15,4 +15,4 @@ function symbolic_to_node(args...; kws...)
     )
 end
 
-end
+end