Peter Krol

"Small, specific instances" refers to the individual typeclass instances of a type constructor. For example, `fromTraversable` uses the `Traversable` instance, and `Array` has one: https://github.com/gcanti/fp-ts/blob/48b3786511aa3413c2f2a4d76311d3b2afa2cd64/src/Array.ts#L1908-L1920 So your code would become...

`t.type` expects all of the specified keys to exist. To make a codec for a record with optional properties, use `t.partial`. These two codecs can be intersected to get what...