We specifically recommend against providing panicing and non-panicking. This causes horrible combinatoric explosions. There's very few exceptions to this (array indexing being the major exception). We do of course recommend non-panicking, but there's a few cases where the burden of checking for errors is too high (indexing, refcell).

We're actually in the midst of arguing whether to violate this convention and do it for RefCell: https://github.com/rust-lang/rust/issues/27733