Mention struct update syntax

Author: ChayimFriedman2

src/language/custom-types/members.md

@@ -314,23 +314,13 @@ Console.WriteLine(pt.ToString()); // prints: Point { X = 789, Y = 456 }
 readonly record struct Point(int X, int Y);
 ```
 
-There is no `with` in Rust, but to emulate something similar in Rust, it has
-to be baked into the type's design:
+There equivalence to `with` in Rust is "struct update syntax" or "functional update syntax":
 
 ```rust
+#[derive(Debug)]
 struct Point { x: i32, y: i32 }
 
-impl Point {
-    pub fn new(x: i32, y: i32) -> Self {
-        Self { x, y }
-    }
-
-    pub fn x(&self) -> i32 { self.x }
-    pub fn y(&self) -> i32 { self.y }
-
-    // following methods consume self and return a new instance
-
-    pub fn set_x(self, val: i32) -> Self { Self::new(val, self.y) }
-    pub fn set_y(self, val: i32) -> Self { Self::new(self.x, val) }
-}
+let mut pt = Point { x: 123, y: 456 };
+pt = Point { x: 789, ..pt };
+println!("{pt:?}");
 ```