Function resolve_arg_string 

fn resolve_arg_string<'tcx>(
    tcx: TyCtxt<'tcx>,
    def_id: DefId,
    param_ty: &str,
    expr: &Expr,
) -> String

Resolve a call-site argument expression to its display form, following the def parameter’s declared role so internal placeholders (e.g. Arg_0 from a JSON contract) render as the actual parameter name.