diff --git a/src/libstd/error.rs b/src/libstd/error.rs
index 6ca8e28c11659..cfc256f3644d7 100644
--- a/src/libstd/error.rs
+++ b/src/libstd/error.rs
@@ -153,6 +153,36 @@ pub trait Error: Debug + Display {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
     /// Converts a type of [`Error`] into a box of dyn [`Error`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::fmt;
+    /// use std::mem;
+    ///
+    /// #[derive(Debug)]
+    /// struct AnError;
+    ///
+    /// impl fmt::Display for AnError {
+    ///     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    ///         write!(f , "An error")
+    ///     }
+    /// }
+    ///
+    /// impl Error for AnError {
+    ///     fn description(&self) -> &str {
+    ///         "Description of an error"
+    ///     }
+    /// }
+    ///
+    /// fn main() {
+    ///     let an_error = AnError;
+    ///     assert!(0 == mem::size_of_val(&an_error));
+    ///     let a_boxed_error = Box::<Error>::from(an_error);
+    ///     assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: E) -> Box<dyn Error + 'a> {
         Box::new(err)
     }
@@ -162,6 +192,41 @@ impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
 impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> {
     /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of dyn [`Error`] +
     /// [`Send`] + [`Sync`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::fmt;
+    /// use std::mem;
+    ///
+    /// #[derive(Debug)]
+    /// struct AnError;
+    ///
+    /// impl fmt::Display for AnError {
+    ///     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+    ///         write!(f , "An error")
+    ///     }
+    /// }
+    ///
+    /// impl Error for AnError {
+    ///     fn description(&self) -> &str {
+    ///         "Description of an error"
+    ///     }
+    /// }
+    ///
+    /// unsafe impl Send for AnError {}
+    ///
+    /// unsafe impl Sync for AnError {}
+    ///
+    /// fn main() {
+    ///     let an_error = AnError;
+    ///     assert!(0 == mem::size_of_val(&an_error));
+    ///     let a_boxed_error = Box::<Error + Send + Sync>::from(an_error);
+    ///     assert!(
+    ///         mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> {
         Box::new(err)
     }
@@ -170,6 +235,20 @@ impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync +
 #[stable(feature = "rust1", since = "1.0.0")]
 impl From<String> for Box<dyn Error + Send + Sync> {
     /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::mem;
+    ///
+    /// fn main() {
+    ///     let a_string_error = "a string error".to_string();
+    ///     let a_boxed_error = Box::<Error + Send + Sync>::from(a_string_error);
+    ///     assert!(
+    ///         mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: String) -> Box<dyn Error + Send + Sync> {
         #[derive(Debug)]
         struct StringError(String);
@@ -191,6 +270,19 @@ impl From<String> for Box<dyn Error + Send + Sync> {
 #[stable(feature = "string_box_error", since = "1.6.0")]
 impl From<String> for Box<dyn Error> {
     /// Converts a [`String`] into a box of dyn [`Error`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::mem;
+    ///
+    /// fn main() {
+    ///     let a_string_error = "a string error".to_string();
+    ///     let a_boxed_error = Box::<Error>::from(a_string_error);
+    ///     assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(str_err: String) -> Box<dyn Error> {
         let err1: Box<dyn Error + Send + Sync> = From::from(str_err);
         let err2: Box<dyn Error> = err1;
@@ -201,6 +293,20 @@ impl From<String> for Box<dyn Error> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, 'b> From<&'b str> for Box<dyn Error + Send + Sync + 'a> {
     /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::mem;
+    ///
+    /// fn main() {
+    ///     let a_str_error = "a str error";
+    ///     let a_boxed_error = Box::<Error + Send + Sync>::from(a_str_error);
+    ///     assert!(
+    ///         mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: &'b str) -> Box<dyn Error + Send + Sync + 'a> {
         From::from(String::from(err))
     }
@@ -209,6 +315,19 @@ impl<'a, 'b> From<&'b str> for Box<dyn Error + Send + Sync + 'a> {
 #[stable(feature = "string_box_error", since = "1.6.0")]
 impl<'a> From<&'a str> for Box<dyn Error> {
     /// Converts a [`str`] into a box of dyn [`Error`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::mem;
+    ///
+    /// fn main() {
+    ///     let a_str_error = "a str error";
+    ///     let a_boxed_error = Box::<Error>::from(a_str_error);
+    ///     assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: &'a str) -> Box<dyn Error> {
         From::from(String::from(err))
     }
@@ -217,6 +336,21 @@ impl<'a> From<&'a str> for Box<dyn Error> {
 #[stable(feature = "cow_box_error", since = "1.22.0")]
 impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
     /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::mem;
+    /// use std::borrow::Cow;
+    ///
+    /// fn main() {
+    ///     let a_cow_str_error = Cow::from("a str error");
+    ///     let a_boxed_error = Box::<Error + Send + Sync>::from(a_cow_str_error);
+    ///     assert!(
+    ///         mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> {
         From::from(String::from(err))
     }
@@ -225,6 +359,20 @@ impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
 #[stable(feature = "cow_box_error", since = "1.22.0")]
 impl<'a> From<Cow<'a, str>> for Box<dyn Error> {
     /// Converts a [`Cow`] into a box of dyn [`Error`].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use std::error::Error;
+    /// use std::mem;
+    /// use std::borrow::Cow;
+    ///
+    /// fn main() {
+    ///     let a_cow_str_error = Cow::from("a str error");
+    ///     let a_boxed_error = Box::<Error>::from(a_cow_str_error);
+    ///     assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+    /// }
+    /// ```
     fn from(err: Cow<'a, str>) -> Box<dyn Error> {
         From::from(String::from(err))
     }