rustdoc/
display.rs

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1//! Various utilities for working with [`fmt::Display`] implementations.
2
3use std::fmt::{self, Display, Formatter};
4
5pub(crate) trait Joined: IntoIterator {
6    /// Takes an iterator over elements that implement [`Display`], and format them into `f`, separated by `sep`.
7    ///
8    /// This is similar to [`Itertools::format`](itertools::Itertools::format), but instead of returning an implementation of `Display`,
9    /// it formats directly into a [`Formatter`].
10    ///
11    /// The performance of `joined` is slightly better than `format`, since it doesn't need to use a `Cell` to keep track of whether [`fmt`](Display::fmt)
12    /// was already called (`joined`'s API doesn't allow it be called more than once).
13    fn joined(self, sep: &str, f: &mut Formatter<'_>) -> fmt::Result;
14}
15
16impl<I, T> Joined for I
17where
18    I: IntoIterator<Item = T>,
19    T: Display,
20{
21    fn joined(self, sep: &str, f: &mut Formatter<'_>) -> fmt::Result {
22        let mut iter = self.into_iter();
23        let Some(first) = iter.next() else { return Ok(()) };
24        first.fmt(f)?;
25        for item in iter {
26            f.write_str(sep)?;
27            item.fmt(f)?;
28        }
29        Ok(())
30    }
31}
32
33pub(crate) trait MaybeDisplay {
34    /// For a given `Option<T: Display>`, returns a `Display` implementation that will display `t` if `Some(t)`, or nothing if `None`.
35    fn maybe_display(self) -> impl Display;
36}
37
38impl<T: Display> MaybeDisplay for Option<T> {
39    fn maybe_display(self) -> impl Display {
40        fmt::from_fn(move |f| {
41            if let Some(t) = self.as_ref() {
42                t.fmt(f)?;
43            }
44            Ok(())
45        })
46    }
47}
rustdoc/display.rs

rustdoc/
display.rs
