2daecf7c45
Clarify safety concern of `io::Read::read` is only relevant in unsafe code We have this clarification note in other similar place like [Iterator::size_hint](https://doc.rust-lang.org/stable/std/iter/trait.Iterator.html#method.size_hint). The lack of clarification might lead to confusion to Rust beginners. [Relevant URLO post](https://users.rust-lang.org/t/can-read-overflow-a-buffer/94347).