Editorial changes. (#120)

Editorial changes.

Author: RalfJung

reference/src/layout/pointers.md

@@ -2,34 +2,33 @@
 
 ### Terminology
 
-Reference types are types of the form `&T`, `&mut T` or `&dyn T`.
+Reference types are types of the form `&T`, `&mut T`.
 
 Raw pointer types are types of the form `*const T` or `*mut T`.
-We write `*T` when the mutability attribute is unimportant.
 
 ### Representation
 
 The alignment of `&T`, `&mut T`, `*const T` and `*mut T` are the same,
 and are at least the word size.
 
-* If `T` is a trait, then the alignment of `&dyn T` is the word size.
 * If `T` is a sized type then the alignment of `&T` is the word size.
+* The alignment of `&dyn Trait` is the word size.
 * The alignment of `&[T]` is the word size.
 * The alignment of `&str` is the word size.
 * Alignment in other cases may be more than the word size (e.g., for other dynamically sized types).
 
 The sizes of `&T`, `&mut T`, `*const T` and `*mut T` are the same,
 and are at least one word.
 
-* If `T` is a trait, then the size of `&dyn T` is two words.
 * If `T` is a sized type then the size of `&T` is one word.
+* The size of `&dyn Trait` is two words.
 * The size of `&[T]` is two words.
 * The size of `&str` is two words.
 * Size in other cases may be more than one word (e.g., for other dynamically sized types).
 
 ### Notes
 
-The layouts of `&T`, `&mut T` and `*T` are the same.
+The layouts of `&T`, `&mut T`, `*const T` and `*mut T` are the same.
 
 If `T` is sized, references and pointers to `T` have a size and alignment of one
 word and have therefore the same layout as C pointers.
@@ -40,25 +39,30 @@ word and have therefore the same layout as C pointers.
 > or, in the case of `&mut T`, aliasing.
 
 We do not make any guarantees about the layout of
-multi-trait objects `&(dyn T + U)` or references to other dynamically sized types,
+multi-trait objects `&(dyn Trait1 + Trait2)` or references to other dynamically sized types,
 other than that they are at least word-aligned, and have size at least one word.
 
-The layout of `&dyn T` when `T` is a trait is the same as that of:
-```rust,ignore
+The layout of `&dyn Trait` when `Trait` is a trait is the same as that of:
+```rust
 #[repr(C)]
 struct DynObject {
-  data: *u8,
-  vtable: *u8,
+  data: *const u8,
+  vtable: *const u8,
 }
 ```
 
+> **note**: In the layout of `&dyn mut Trait` the field `data` is of the type `*mut u8`.
+
 The layout of `&[T]` is the same as that of:
-```rust,ignore
+```rust
 #[repr(C)]
 struct Slice<T> {
-  ptr: *T,
+  ptr: *const T,
   len: usize,
 }
 ```
 
-The layout of `&str` is the same as that of `&[u8]`.
+> **note**: In the layout of `&mut [T]` the field `ptr` is of the type `*mut T`.
+
+The layout of `&str` is the same as that of `&[u8]`, and the layout of `&mut str` is
+the same as that of `&mut [u8]`.