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kennytmkennytm
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Rollup merge of rust-lang#53523 - phungleson:fix-impl-from-for-std-error, r=GuillaumeGomez
Add doc for impl From for Std Error As part of issue rust-lang#51430 (cc @skade). I am not sure if it is going to a correct direction so put up here so that people can comment.
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‎src/libstd/error.rs‎

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@@ -217,20 +217,97 @@ pub trait Error: Debug + Display {
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
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/// Converts a type of [`Error`] into a box of dyn [`Error`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::fmt;
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/// use std::mem;
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///
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/// #[derive(Debug)]
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/// struct AnError;
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///
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/// impl fmt::Display for AnError {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f , "An error")
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/// }
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/// }
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///
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/// impl Error for AnError {
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/// fn description(&self) -> &str {
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/// "Description of an error"
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/// }
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/// }
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///
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/// let an_error = AnError;
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/// assert!(0 == mem::size_of_val(&an_error));
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/// let a_boxed_error = Box::<Error>::from(an_error);
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/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: E) -> Box<dyn Error + 'a> {
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Box::new(err)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> {
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/// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of dyn [`Error`] +
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/// [`Send`] + [`Sync`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::fmt;
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/// use std::mem;
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///
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/// #[derive(Debug)]
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/// struct AnError;
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///
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/// impl fmt::Display for AnError {
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/// fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
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/// write!(f , "An error")
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/// }
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/// }
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///
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/// impl Error for AnError {
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/// fn description(&self) -> &str {
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/// "Description of an error"
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/// }
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/// }
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///
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/// unsafe impl Send for AnError {}
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///
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/// unsafe impl Sync for AnError {}
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///
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/// let an_error = AnError;
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/// assert!(0 == mem::size_of_val(&an_error));
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/// let a_boxed_error = Box::<Error + Send + Sync>::from(an_error);
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/// assert!(
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/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> {
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Box::new(err)
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}
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}
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#[stable(feature = "rust1", since = "1.0.0")]
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impl From<String> for Box<dyn Error + Send + Sync> {
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/// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::mem;
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///
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/// let a_string_error = "a string error".to_string();
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/// let a_boxed_error = Box::<Error + Send + Sync>::from(a_string_error);
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/// assert!(
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/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: String) -> Box<dyn Error + Send + Sync> {
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#[derive(Debug)]
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struct StringError(String);
@@ -251,6 +328,18 @@ impl From<String> for Box<dyn Error + Send + Sync> {
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#[stable(feature = "string_box_error", since = "1.6.0")]
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impl From<String> for Box<dyn Error> {
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/// Converts a [`String`] into a box of dyn [`Error`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::mem;
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///
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/// let a_string_error = "a string error".to_string();
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/// let a_boxed_error = Box::<Error>::from(a_string_error);
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/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(str_err: String) -> Box<dyn Error> {
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let err1: Box<dyn Error + Send + Sync> = From::from(str_err);
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let err2: Box<dyn Error> = err1;
@@ -260,27 +349,79 @@ impl From<String> for Box<dyn Error> {
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#[stable(feature = "rust1", since = "1.0.0")]
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impl<'a, 'b> From<&'b str> for Box<dyn Error + Send + Sync + 'a> {
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/// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::mem;
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///
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/// let a_str_error = "a str error";
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/// let a_boxed_error = Box::<Error + Send + Sync>::from(a_str_error);
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/// assert!(
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/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: &'b str) -> Box<dyn Error + Send + Sync + 'a> {
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From::from(String::from(err))
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}
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}
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#[stable(feature = "string_box_error", since = "1.6.0")]
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impl<'a> From<&'a str> for Box<dyn Error> {
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/// Converts a [`str`] into a box of dyn [`Error`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::mem;
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///
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/// let a_str_error = "a str error";
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/// let a_boxed_error = Box::<Error>::from(a_str_error);
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/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: &'a str) -> Box<dyn Error> {
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From::from(String::from(err))
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}
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}
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#[stable(feature = "cow_box_error", since = "1.22.0")]
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impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
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/// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::mem;
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/// use std::borrow::Cow;
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///
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/// let a_cow_str_error = Cow::from("a str error");
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/// let a_boxed_error = Box::<Error + Send + Sync>::from(a_cow_str_error);
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/// assert!(
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/// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> {
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From::from(String::from(err))
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}
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}
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#[stable(feature = "cow_box_error", since = "1.22.0")]
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impl<'a> From<Cow<'a, str>> for Box<dyn Error> {
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/// Converts a [`Cow`] into a box of dyn [`Error`].
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///
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/// # Examples
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///
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/// ```
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/// use std::error::Error;
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/// use std::mem;
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/// use std::borrow::Cow;
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///
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/// let a_cow_str_error = Cow::from("a str error");
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/// let a_boxed_error = Box::<Error>::from(a_cow_str_error);
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/// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
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/// ```
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fn from(err: Cow<'a, str>) -> Box<dyn Error> {
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From::from(String::from(err))
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}

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