Consider opting for unsafe_op_in_unsafe_fn #285

#![warn(unsafe_op_in_unsafe_fn)] will no longer make unsafe fn imply a unsafe {} surrounding the body. We should consider switching it on to make all unsafe operations explicit, even inside unsafe fn. This will ensure that all operations in unsafe fn still have their invariants audited and upheld.

This feature is stablised in Rust 1.52 so we may want a newer version of Rust nightly.