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