# Unsafety

Unsafe operations are those that can potentially violate the memory-safety guarantees of Rust's static semantics.

The following language level features cannot be used in the safe subset of Rust:

- Dereferencing a raw pointer.
- Reading or writing a mutable or external static variable.
- Accessing a field of a `union`, other than to assign to it.
- Calling an unsafe function (including an intrinsic or foreign function).
- Implementing an unsafe trait.