A long time ago non-panicking `unwrap` methods were renamed to `into_inner` in this Pull Request: https://github.com/rust-lang/rust/pull/19149
Looks like this doc comment was not updated however.
///
/// Seeking always discards the internal buffer, even if the seek position
/// would otherwise fall within it. This guarantees that calling
- /// `.unwrap()` immediately after a seek yields the underlying reader at
- /// the same position.
+ /// `.into_inner()` immediately after a seek yields the underlying reader
+ /// at the same position.
///
/// See `std::io::Seek` for more details.
///