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use core::fmt::Display;
#[cfg(feature = "std")]
use std::path::{self, Path, PathBuf};
#[doc(hidden)]
pub trait AsDisplay<'a>: Sealed {
// TODO: convert to generic associated type.
// https://github.com/dtolnay/thiserror/pull/253
type Target: Display;
fn as_display(&'a self) -> Self::Target;
}
impl<'a, T> AsDisplay<'a> for &T
where
T: Display + ?Sized + 'a,
{
type Target = &'a T;
fn as_display(&'a self) -> Self::Target {
*self
}
}
#[cfg(feature = "std")]
impl<'a> AsDisplay<'a> for Path {
type Target = path::Display<'a>;
#[inline]
fn as_display(&'a self) -> Self::Target {
self.display()
}
}
#[cfg(feature = "std")]
impl<'a> AsDisplay<'a> for PathBuf {
type Target = path::Display<'a>;
#[inline]
fn as_display(&'a self) -> Self::Target {
self.display()
}
}
#[doc(hidden)]
pub trait Sealed {}
impl<T: Display + ?Sized> Sealed for &T {}
#[cfg(feature = "std")]
impl Sealed for Path {}
#[cfg(feature = "std")]
impl Sealed for PathBuf {}
// Add a synthetic second impl of AsDisplay to prevent the "single applicable
// impl" rule from making too weird inference decision based on the single impl
// for &T, which could lead to code that compiles with thiserror's std feature
// off but breaks under feature unification when std is turned on by an
// unrelated crate.
#[cfg(not(feature = "std"))]
mod placeholder {
use super::{AsDisplay, Sealed};
use core::fmt::{self, Display};
pub struct Placeholder;
impl<'a> AsDisplay<'a> for Placeholder {
type Target = Self;
#[inline]
fn as_display(&'a self) -> Self::Target {
Placeholder
}
}
impl Display for Placeholder {
fn fmt(&self, _formatter: &mut fmt::Formatter) -> fmt::Result {
unreachable!()
}
}
impl Sealed for Placeholder {}
}
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