Use "extending expression" wording.

Author: m-ou-se

src/destructors.md

@@ -374,7 +374,7 @@ expression which is one of the following:
   expression], [braced struct][struct expression], or [tuple][tuple expression]
   expression.
 * The final expression of any extending [block expression].
-* The arguments to [tuple struct] and [tuple variant] constructors.
+* The arguments to an extending [tuple struct] or [tuple variant] constructor expression.
 
 So the borrow expressions in `&mut 0`, `(&1, &mut 2)`, and `Some(&mut 3)`
 are all extending expressions. The borrows in `&0 + &1` and `f(&mut 0)` are not.