Rollup merge of #140791 - xizheyin:issue-140761, r=ibraheemdev

std: explain prefer `TryInto` over `TryFrom` when specifying traits bounds on generic function

Fixes #140761

This PR keeps the explanations of `Into` and `From` consistent and adds explanations for `TryInto` and `TryFrom`.

r? libs

Author: matthiaskrgr

library/core/src/convert/mod.rs

@@ -464,8 +464,8 @@ pub trait Into<T>: Sized {
 /// orphaning rules.
 /// See [`Into`] for more details.
 ///
-/// Prefer using [`Into`] over using `From` when specifying trait bounds on a generic function.
-/// This way, types that directly implement [`Into`] can be used as arguments as well.
+/// Prefer using [`Into`] over [`From`] when specifying trait bounds on a generic function
+/// to ensure that types that only implement [`Into`] can be used as well.
 ///
 /// The `From` trait is also very useful when performing error handling. When constructing a function
 /// that is capable of failing, the return type will generally be of the form `Result<T, E>`.
@@ -597,6 +597,9 @@ pub trait From<T>: Sized {
 /// standard library. For more information on this, see the
 /// documentation for [`Into`].
 ///
+/// Prefer using [`TryInto`] over [`TryFrom`] when specifying trait bounds on a generic function
+/// to ensure that types that only implement [`TryInto`] can be used as well.
+///
 /// # Implementing `TryInto`
 ///
 /// This suffers the same restrictions and reasoning as implementing
@@ -636,6 +639,9 @@ pub trait TryInto<T>: Sized {
 /// When the [`!`] type is stabilized [`Infallible`] and [`!`] will be
 /// equivalent.
 ///
+/// Prefer using [`TryInto`] over [`TryFrom`] when specifying trait bounds on a generic function
+/// to ensure that types that only implement [`TryInto`] can be used as well.
+///
 /// `TryFrom<T>` can be implemented as follows:
 ///
 /// ```