typo

Author: RalfJung

src/items/unions.md

@@ -40,7 +40,7 @@ let f = u.f1;
 Unions have no notion of an "active field".  Instead, every union access just
 interprets the storage at the type of the field used for the access.  Reading a
 union field is equivalent to a [`transmute`]: The data in the union, no matter
-how it was stored there, is transmuted to the type if the field.  Reading data
+how it was stored there, is transmuted to the type of the field.  Reading data
 at a bad type results in undefined behavior (for example, reading the value `3`
 at type `bool`).  For this reason, all reads of union fields have to be placed
 in `unsafe` blocks: