Merge pull request #1339 from tshepang/patch-2

fix typo

Author: ehuss

src/items/unions.md

@@ -61,7 +61,7 @@ non-zero offset (except when [the C representation] is used); in that case the
 bits starting at the offset of the fields are read. It is the programmer's
 responsibility to make sure that the data is valid at the field's type. Failing
 to do so results in [undefined behavior]. For example, reading the value `3`
-through of a field of the [boolean type] is undefined behavior. Effectively,
+from a field of the [boolean type] is undefined behavior. Effectively,
 writing to and then reading from a union with [the C representation] is
 analogous to a [`transmute`] from the type used for writing to the type used for
 reading.