Doc: "unsafe turns off safety checks" is misleading

[SimonSapin]

http://doc.rust-lang.org/intro.html#a-footnote:-unsafe currently says:

Within an unsafe block, Rust turns off many of its safety checks.

This is misleading and should not be in the documentation. For example, unsafe {} does not let you use a moved value. Instead, it lets you use features (such as raw pointers and transmute) that are otherwise forbidden.

[steveklabnik]

I agree we should be more clear that only a few restrictions are technically lifted, it's not like you drop straight into assembly or something in unsafe blocks.

[thestinger]

you only have to audit what you've done inside unsafe, and not the entire program itself.

This isn't true. You have to audit all code inside unsafe and all safe code trusted by unsafe code. For example, unsafe blocks in Vec<T> methods implicitly trust all safe code in the module (since it can modify the fields incorrectly) along with all safe code they call directly. The existence of a clear safety boundary in Rust is overstated.

[steveklabnik]

This language has been removed with the merger of #16641