You're right that '[i]' is just a function call ('.index(i)' https://doc.rust-lang.org/std/ops/trait.Index.html https://doc.rust-lang.org/std/ops/trait.Index.ht

You're right that '[i]' is just a function call ('.index(i)' https://doc.rust-lang.org/std/ops/trait.Index.html https://doc.rust-lang.org/std/ops/trait.Index.html). > So, for me, the placing of bounds checks when using that function is an implementation detail and therefore, if unsafe removes it, it does not effect the semantics. The function is not marked as unsafe, so it promises that it will not corrupt memory and thus must perform bound checks. The designation of safe/unsafe for a function is compile-time and promises certain semantics. It would be a semantic issue for a safe function to invoke unsafe behavior. Even within an 'unsafe' block, calling safe functions should not cause memory corruption as long as your other unsafe calls / unsafe code didn't do anything "wrong". Anyway, to implement a function like that, you'd need: fn index(i) -> T { if is_caller_in_unsafe_block() { return unsafe { unsafe_index(i) } } ... } The compiler does not, as far as I'm aware, have any "is_caller_in_unsafe_block" primitive, and adding one seems quite fraught.