Merge pull request #21038 from steveklabnik/gh20471

Elaborate on destructuring let

Reviewed-by: alexcrichton

Author: bors

src/doc/trpl/compound-data-types.md

@@ -194,7 +194,8 @@ println!("length is {} inches", integer_length);
 ```
 
 As you can see here, you can extract the inner integer type through a
-destructuring `let`.
+destructuring `let`, as we discussed previously in 'tuples.' In this case, the
+`let Inches(integer_length)` assigns `10` to `integer_length`.
 
 ## Enums