PathBuf::set_extension accepts an extension containing slashes

[oconnor663]

The following code runs without any errors:

let mut p = Path::new("myfile.pdf").to_owned();
p.set_extension("txt/doc");
println!("{:?} {}", p, p.components().count());
// "myfile.txt/doc" 2

I'm not sure what I expected this to do. Maybe panic? I would also have been ok with short-circuiting and returning false. But succeeding feels weird to me.

The set_file_name method has a similar problem. There's no return value on that one, so panicking might be the only option, if we don't like allowing slashes in the new filename.

[oconnor663]

Some discussion at https://www.reddit.com/r/rust/comments/4bviym/odd_behavior_of_functions_in_pathbuf_module/.

[steveklabnik]

Triage: not aware of any changes.

[tbu-]

Fixed in #125070 by panicking if the "extension" contains slashes.

[ChrisDenton]

Closing as complete for that reason.