Function order_declarations 

pub fn order_declarations(
    program: &Program,
    require_contiguous_modules: bool,
) -> Result<Vec<&Decl>>

Declarations in an order where each follows everything it uses.

Source order is kept where possible and, among ready declarations, the ones in the module being emitted come first so modules stay contiguous.

Errors

On cyclic declarations, and on modules that would have to be reopened when require_contiguous_modules is set.