Add test and fix typo

Author: YingboMa

src/systems/abstractsystem.jl

@@ -358,12 +358,13 @@ function Base.setproperty!(sys::AbstractSystem, prop::Symbol, val)
 end
 
 function apply_to_variables(f::F, ex) where {F}
+    ex = value(ex)
     if isvariable(ex)
         return f(ex)
     end
     istree(ex) || return ex
-    similarterm(ex, apply_to_variables(operation(ex)),
-                map(apply_to_variables, arguments(ex)),
+    similarterm(ex, apply_to_variables(f, operation(ex)),
+                map(Base.Fix1(apply_to_variables, f), arguments(ex)),
                 metadata = metadata(ex))
 end
 

test/variable_scope.jl

@@ -1,4 +1,6 @@
 using ModelingToolkit
+using ModelingToolkit: SymScope
+using Symbolics: arguments, value
 using Test
 
 @parameters t
@@ -13,6 +15,9 @@ LocalScope(e.val)
 ParentScope(e.val)
 GlobalScope(e.val)
 
+ie = ParentScope(1 / e)
+@test getmetadata(arguments(value(ie))[2], SymScope) === ParentScope(LocalScope())
+
 eqs = [0 ~ a
        0 ~ b
        0 ~ c