Section 3.2 should introduce the unit type, ()

[acuster]

The unit type, (), is introduced in passing in the struct chapter rather than in the tuple type section
of data types chapter.

It would make more sense to introduce it explicitly early on, and mention its general importance as an implicit, default expression.

[ChrisKeefe]

Glad to see this is already on your radar! I went digging for information on the unit type after reading about unit-like structs, and was surprised when there was no information in chs 3.2 or 19.3.