There is no such "compiler flag" in Rust, that's only a C# thing.

But also more relevantly here, stuff you'd be calling in those Rust blocks tends to have longer names and often calls out the fact it's specifically not checked, e.g.

  a = b.unchecked_add(c); // Like a C or C++ arithmetic operation if you overflow it's UB. This might be faster. It might not. But if you must have this anyway, that's how

  n = NonZeroU32::new_unchecked(0); // Unlike new() which returns None because duh, zero isn't non-zero, this results in UB.

Not all of them though, for example:

  v = Vec::from_raw_parts(ptr, len, cap); // Make a Vec, the pointer ptr had better actually be pointing at contiguous memory for exactly cap item-sized slots, the first len of which are in fact legitimately values of the appropriate type, if any of this is wrong that's immediately UB.

While sadly it does not require a flag to enable, at least you can turn it off with: `#![forbid(unsafe_code)]`.