Function nested_call_context 

fn nested_call_context<'tcx>(
    body: &Body<'tcx>,
    args: &[Spanned<Operand<'tcx>>],
    context: &CallContext,
) -> CallContext

Build the CallContext a nested call sees, keyed by the nested callee’s own argument indices. Each nested argument is concrete either because it is a literal at this call site, or because it passes an outer concrete value straight through (Copy/Move of an argument). This keeps a caller’s literal at position i from being read as the nested callee’s position-i argument.