Incorrect discovery of parameters in hierarchical systems (V9)

[isaacsas]

This came from a MTK MWE derived from a Catalyst bug that was reported on Discourse:

https://discourse.julialang.org/t/issue-with-scoping-rules-of-parameter-and-variable-declaration-in-components-catalyst-vs-modelingtoolkit/130232/4

@mtkmodel Decl1 begin
    @parameters begin
        k = 1.0
    end
    @variables begin
        x(t) = k
    end
end

@mtkmodel Decl2 begin
    @parameters begin
        k = 2.0
    end
    @variables begin
        x(t) = k
    end
end

@named m1 = Decl1()
@named m2 = Decl2()
@named sys1  = ODESystem([D(m2.x) ~ 0, D(m1.x) ~ 0], t; systems = [m1, m2])

giving

Model sys1:
Subsystems (2): see hierarchy(sys1)
  m1
  m2
Equations (2):
  2 standard: see equations(sys1)
Unknowns (2): see unknowns(sys1)
  m2₊x(t) [defaults to k]
  m1₊x(t) [defaults to k]
Parameters (3): see parameters(sys1)
  k [defaults to 1.0]
  m1₊k [defaults to 1.0]
  m2₊k [defaults to 2.0]

MTK seems to be adding a new top-level parameter k too instead of just the versions in the two subsystems.

[AayushSabharwal]

It seems this happens because m1.x and m2.x have the default k in their metadata, so when the system looks through the variable metadata, it encounters k and adds it to the parameters.

[isaacsas]

Right, so the scoping information on k is being lost (or just not generated correctly) when collecting variables/parameters?