Using the "as" keyword to cast numbers in Rust can cause silent data loss between incompatible numeric types (e.g. usize -> i32). Monguard should lint for clippy::cast_possible_truncation, clippy::cast_possible_wrap, and clippy::cast_sign_loss to force callers to handle these conversions explicitly. See RUST-1881 and RUST-2127 for similar work in the Rust driver; it might be useful to vendor in the Checked type.