Rollup merge of rust-lang#30952 - jonastepe:nomicon_vec_zst_code_fix, r=Gankro

* Moved semicolon to the right place in the `let` statement in the ZST section.
* Fixed the missing ZST additions for `RawValIter<T>` from this section in the final code section.

Author: Manishearth

src/doc/nomicon/vec-final.md

@@ -226,7 +226,11 @@ impl<T> Iterator for RawValIter<T> {
         } else {
             unsafe {
                 let result = ptr::read(self.start);
-                self.start = self.start.offset(1);
+                self.start = if mem::size_of::<T>() == 0 {
+                    (self.start as usize + 1) as *const _
+                } else {
+                    self.start.offset(1)
+                };
                 Some(result)
             }
         }
@@ -246,7 +250,11 @@ impl<T> DoubleEndedIterator for RawValIter<T> {
             None
         } else {
             unsafe {
-                self.end = self.end.offset(-1);
+                self.end = if mem::size_of::<T>() == 0 {
+                    (self.end as usize - 1) as *const _
+                } else {
+                    self.end.offset(-1)
+                };
                 Some(ptr::read(self.end))
             }
         }

src/doc/nomicon/vec-zsts.md

@@ -140,8 +140,8 @@ impl<T> Iterator for RawValIter<T> {
                 self.start = if mem::size_of::<T>() == 0 {
                     (self.start as usize + 1) as *const _
                 } else {
-                    self.start.offset(1);
-                }
+                    self.start.offset(1)
+                };
                 Some(result)
             }
         }
@@ -164,8 +164,8 @@ impl<T> DoubleEndedIterator for RawValIter<T> {
                 self.end = if mem::size_of::<T>() == 0 {
                     (self.end as usize - 1) as *const _
                 } else {
-                    self.end.offset(-1);
-                }
+                    self.end.offset(-1)
+                };
                 Some(ptr::read(self.end))
             }
         }