rust book: syntax simplications from (autoderef?)

src/doc/trpl/ownership.md

@@ -207,7 +207,8 @@ We have to change our `main` a bit too:
 
 ```rust
 fn main() {
-    let mut x = 5;
+    let mut x = 5; // FIXME: remove this line?
+    // let mut x = Box::new(5);  // This (box), used in previous exampl(s),  still works
 
     add_one(&mut x);
 

src/doc/trpl/pointers.md

@@ -454,7 +454,8 @@ fn box_succ(x: Box<i32>) -> i32 { *x + 1 }
 fn rc_succ(x: Rc<i32>) -> i32 { *x + 1 }
 ```
 
-Note that the caller of your function will have to modify their calls slightly:
+Note that the caller of your function will have to modify their calls slightly 
+(FIXME: actually they don't):
 
 ```{rust}
 use std::rc::Rc;
@@ -466,8 +467,8 @@ let box_x = Box::new(5);
 let rc_x = Rc::new(5);
 
 succ(ref_x);
-succ(&*box_x);
-succ(&*rc_x);
+succ(&*box_x);  // FIXME: actually &box_x works fine
+succ(&*rc_x);  // FIXME: actually &rc_x works fine
 ```
 
 The initial `*` dereferences the pointer, and then `&` takes a reference to
@@ -560,38 +561,40 @@ fn main() {
 In this case, Rust knows that `x` is being *borrowed* by the `add_one()`
 function, and since it's only reading the value, allows it.
 
-We can borrow `x` multiple times, as long as it's not simultaneous:
+We can borrow `x` as read-only multiple times, even simultaneously:
 
 ```{rust}
-fn add_one(x: &i32) -> i32 {
-    *x + 1
+fn add(x: &i32, y: &i32) -> i32 {
+    *x + *y
 }
 
 fn main() {
     let x = Box::new(5);
 
-    println!("{}", add_one(&*x));
-    println!("{}", add_one(&*x));
-    println!("{}", add_one(&*x));
+    println!("{}", add(&x, &x));
+    println!("{}", add(&x, &x));
 }
 ```
 
-Or as long as it's not a mutable borrow. This will error:
+We can mutably borrow `x` multiple times, but only if x itself is mutable, and
+it may not be *simultaneously* borrowed: 
 
 ```{rust,ignore}
-fn add_one(x: &mut i32) -> i32 {
-    *x + 1
+fn increment(x: &mut i32) {
+    *x += 1;
 }
 
 fn main() {
-    let x = Box::new(5);
+    // If variable x is not "mut", this will not compile
+    let mut x = Box::new(5);
 
-    println!("{}", add_one(&*x)); // error: cannot borrow immutable dereference
-                                  // of `&`-pointer as mutable
+    increment(&mut x);
+    increment(&mut x);
+    println!("{}", x);
 }
 ```
 
-Notice we changed the signature of `add_one()` to request a mutable reference.
+Notice the signature of `increment()` requests a mutable reference.
 
 ## Best practices