Function nested_fixed_state 

pub fn nested_fixed_state(
    top_params: &Value,
    rest: &str,
    document: &Value,
) -> Result<bool, String>

A nested occurrence’s Fix/Float as the assembly solve reads it.

top_params is the top-level instance’s inputParams, rest the occurrence’s path inside it (ACOMP2, ACOMP1:ACOMP2) and document the definition that instance places. Only an occurrence the solve moves can be fixed or freed here: every instance above it must be flexible (a rigid sub-assembly moves as one body, its parts never move on their own). The state is the instance’s own flexibleFixed[rest], else the grounding of the definition that places it (an explicit isFixed, else the first component, else a Fixed constraint’s target), as assembly::flexible decides it.