thiserror/
display.rs

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1use core::fmt::Display;
2#[cfg(feature = "std")]
3use std::path::{self, Path, PathBuf};
4
5#[doc(hidden)]
6pub trait AsDisplay<'a>: Sealed {
7    // TODO: convert to generic associated type.
8    // https://github.com/dtolnay/thiserror/pull/253
9    type Target: Display;
10
11    fn as_display(&'a self) -> Self::Target;
12}
13
14impl<'a, T> AsDisplay<'a> for &T
15where
16    T: Display + ?Sized + 'a,
17{
18    type Target = &'a T;
19
20    fn as_display(&'a self) -> Self::Target {
21        *self
22    }
23}
24
25#[cfg(feature = "std")]
26impl<'a> AsDisplay<'a> for Path {
27    type Target = path::Display<'a>;
28
29    #[inline]
30    fn as_display(&'a self) -> Self::Target {
31        self.display()
32    }
33}
34
35#[cfg(feature = "std")]
36impl<'a> AsDisplay<'a> for PathBuf {
37    type Target = path::Display<'a>;
38
39    #[inline]
40    fn as_display(&'a self) -> Self::Target {
41        self.display()
42    }
43}
44
45#[doc(hidden)]
46pub trait Sealed {}
47impl<T: Display + ?Sized> Sealed for &T {}
48#[cfg(feature = "std")]
49impl Sealed for Path {}
50#[cfg(feature = "std")]
51impl Sealed for PathBuf {}
52
53// Add a synthetic second impl of AsDisplay to prevent the "single applicable
54// impl" rule from making too weird inference decision based on the single impl
55// for &T, which could lead to code that compiles with thiserror's std feature
56// off but breaks under feature unification when std is turned on by an
57// unrelated crate.
58#[cfg(not(feature = "std"))]
59mod placeholder {
60    use super::{AsDisplay, Sealed};
61    use core::fmt::{self, Display};
62
63    pub struct Placeholder;
64
65    impl<'a> AsDisplay<'a> for Placeholder {
66        type Target = Self;
67
68        #[inline]
69        fn as_display(&'a self) -> Self::Target {
70            Placeholder
71        }
72    }
73
74    impl Display for Placeholder {
75        fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
76            unreachable!()
77        }
78    }
79
80    impl Sealed for Placeholder {}
81}
thiserror/display.rs

thiserror/
display.rs
