mention the possibility of using enum constructors as functions in expressions

[nliberg]

Neither the nightly Rust reference nor the book seem to mention the fact that one can use enum constructors in a function like way inside expressions, eg. my_iterator.map(Option::Some).

(unless I'm mistaken and it's there somewhere, but I didn't find it)

[steveklabnik]

It's maybe obliquely mentioned at best.

[shepmaster]

IMO, this is two parts:

1. stating that enum constructors are functions.
2. stating that functions can be used where Fn* traits are.

I don't know how much you need to go into every permutation of every feature in Rust ^_^