From 21b4dd14b696420c157192b311dd1f998a58ce88 Mon Sep 17 00:00:00 2001
From: laazy <laaazy@sjtu.edu.cn>
Date: Sat, 23 Mar 2024 23:24:12 +0800
Subject: [PATCH] =?UTF-8?q?=F0=9F=9A=A7=20complete=20last=20one?=
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---
 exercises/23_conversions/as_ref_mut.rs | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/exercises/23_conversions/as_ref_mut.rs b/exercises/23_conversions/as_ref_mut.rs
index 5eb8cd6f..ed53b957 100644
--- a/exercises/23_conversions/as_ref_mut.rs
+++ b/exercises/23_conversions/as_ref_mut.rs
@@ -7,12 +7,10 @@
 // Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a
 // hint.
 
-// I AM NOT DONE
+use std::ops::DerefMut;
 
-use std::ops::Mul;
 
 // Obtain the number of bytes (not characters) in the given argument.
-// TODO: Add the AsRef trait appropriately as a trait bound.
 fn byte_counter<T>(arg: T) -> usize 
 where T: AsRef<str>
 {
@@ -20,7 +18,6 @@ where T: AsRef<str>
 }
 
 // Obtain the number of characters (not bytes) in the given argument.
-// TODO: Add the AsRef trait appropriately as a trait bound.
 fn char_counter<T>(arg: T) -> usize 
 where T: AsRef<str>
 {
@@ -29,11 +26,12 @@ where T: AsRef<str>
 
 // Squares a number using as_mut().
 // TODO: Add the appropriate trait bound.
-fn num_sq<T>(arg: &mut T) 
-where T: for<'a> AsMut<&'a mut Box<u32>> + for<'a> Mul<&'a mut T, Output = T>// + std::ops::MulAssign<&mut Box<u32>>
+fn num_sq<T>(arg: &mut T)
+// where T: DerefMut<Target = u32>,
+where T: AsMut<u32>
 {
     // TODO: Implement the function body.
-    *arg = (*arg) * arg;
+    *arg.as_mut() = *arg.as_mut() * *arg.as_mut();
 }
 
 #[cfg(test)]