diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs index f64f2fb3e9fa..4716aea1cdd5 100644 --- a/src/libcore/convert.rs +++ b/src/libcore/convert.rs @@ -361,11 +361,12 @@ pub trait From: Sized { /// An attempted conversion that consumes `self`, which may or may not be /// expensive. /// -/// Library authors should not directly implement this trait, but should prefer -/// implementing the [`TryFrom`] trait, which offers greater flexibility and -/// provides an equivalent `TryInto` implementation for free, thanks to a -/// blanket implementation in the standard library. For more information on this, -/// see the documentation for [`Into`]. +/// Library authors should usually not directly implement this trait, +/// but should prefer implementing the [`TryFrom`] trait, which offers +/// greater flexibility and provides an equivalent `TryInto` +/// implementation for free, thanks to a blanket implementation in the +/// standard library. For more information on this, see the +/// documentation for [`Into`]. /// /// # Implementing `TryInto` /// @@ -396,7 +397,7 @@ pub trait TryInto: Sized { /// This might be handled by truncating the `i64` to an `i32` (essentially /// giving the `i64`'s value modulo `i32::MAX`) or by simply returning /// `i32::MAX`, or by some other method. The `From` trait is intended -/// for lossless conversions, so the `TryFrom` trait informs the +/// for perfect conversions, so the `TryFrom` trait informs the /// programmer when a type conversion could go bad and lets them /// decide how to handle it. /// @@ -404,7 +405,8 @@ pub trait TryInto: Sized { /// /// - `TryFrom for U` implies [`TryInto`]` for T` /// - [`try_from`] is reflexive, which means that `TryFrom for T` -/// is implemented +/// is implemented and cannot fail -- the associated `Error` type for +/// calling `T::try_from()` on a value of type `T` is `!`. /// /// # Examples /// @@ -417,12 +419,18 @@ pub trait TryInto: Sized { /// let smaller_number = big_number as i32; /// assert_eq!(smaller_number, -727379968); /// +/// // Returns an error because `big_number` is too big to +/// // fit in an `i32`. /// let try_smaller_number = i32::try_from(big_number); /// assert!(try_smaller_number.is_err()); /// +/// // Returns `Ok(3)`. /// let try_successful_smaller_number = i32::try_from(3); /// assert!(try_successful_smaller_number.is_ok()); /// ``` +/// +/// [`try_from`]: trait.TryFrom.html#tymethod.try_from +/// [`TryInto`]: trait.TryInto.html #[stable(feature = "try_from", since = "1.34.0")] pub trait TryFrom: Sized { /// The type returned in the event of a conversion error.