Lifetime documentation should include an example where the lifetime of a return is dependent on two arguments

[brianquinlan]

The document page:
https://doc.rust-lang.org/book/lifetimes.html

For example:
fn <'a>a_or_b(a : &'a str, b : &'a str) -> &'a str

[steveklabnik]

There is an example of the syntax in the elision section, but you're right that more and better examples would be good here, for sure.

[brianquinlan]

What example were you thinking of? I couldn't see one.

[steveklabnik]

Oh, two of the same! I was looking at

fn frob(s: &str, t: &str) -> &str; // ILLEGAL, two inputs
fn frob<'a, 'b>(s: &'a str, t: &'b str) -> &str; // Expanded: Output lifetime is unclear

which has two lifetimes, they're just different ones

[brianquinlan]

Yes, two of the same. I guessed the syntax would be:
fn <'a,'b>a_or_b(a : &'a str, b : &'b str) -> &'a 'b str

but I was wrong :-)