uncons_while should take an item reference

[ncalexan]

I'd like to understand some of the API decisions the library makes. Like in #74 , my motivating use case is to parse a token stream (not a character stream), and my tokens do not implement Copy because they include String data, like:

struct Token {
    Keyword(String),
    ...
}

While implementing RangeStream for a newtype wrapping &'a [Token] (like SliceStream but with item type Token rather item type &'a Token), I've run into the following question. Why does uncons_while take an FnMut(Item) rather than FnMut(&Item) at https://github.com/Marwes/combine/blob/master/src/primitives.rs#L562?

In general, the Rust-y pattern seems to be that predicate filters take references to the elements in their containing collection -- but I'm not an experienced Rust user so I'm probably missing something. Any guidance appreciated.

[Marwes]

Summed together both answers in #74 (comment) since it is more or less the same reason.

[ncalexan]

Summed together both answers in #74 (comment) since it is more or less the same reason.

Thanks for your very useful answer. I think this can just be closed with a link to #44 (comment) which justifies the ergonomics and a link to #74 (comment) which justifies the performance assumptions.