test: test properly scoped discovery of parameters

Author: AayushSabharwal

test/variable_scope.jl

@@ -1,6 +1,6 @@
 using ModelingToolkit
-using ModelingToolkit: SymScope
-using Symbolics: arguments, value
+using ModelingToolkit: SymScope, t_nounits as t, D_nounits as D
+using Symbolics: arguments, value, getname
 using Test
 
 @independent_variables t
@@ -84,3 +84,22 @@ arr1 = ODESystem(Equation[], t, [], []; name = :arr1) ∘ arr0
 arr_ps = ModelingToolkit.getname.(parameters(arr1))
 @test isequal(arr_ps[1], Symbol("xx"))
 @test isequal(arr_ps[2], Symbol("arr0₊xx"))
+
+function Foo(; name, p = 1)
+    @parameters p = p
+    @variables x(t)
+    return ODESystem(D(x) ~ p, t; name)
+end
+function Bar(; name, p = 2)
+    @parameters p = p
+    @variables x(t)
+    @named foo = Foo(; p)
+    return ODESystem(D(x) ~ p + t, t; systems = [foo], name)
+end
+@named bar = Bar()
+bar = complete(bar)
+@test length(parameters(bar)) == 2
+@test sort(getname.(parameters(bar))) == [:foo₊p, :p]
+defs = ModelingToolkit.defaults(bar)
+@test defs[bar.p] == 2
+@test isequal(defs[bar.foo.p], bar.p)