Custom types

When none of the 264 built-in types is the thing you need, register your own — by value set or by function.

synth.RegisterSet("cinema", "Inception", "Interstellar", "Tenet", "Dune")
synth.Register("rating", func(r synth.R) any { return r.IntRange(1, 5) })

Then use the name like any built-in kind:

type Screening struct {
    Film   string `synth:"cinema"`
    Rating int    `synth:"rating"`
}

fields:
  film:   { kind: cinema }
  rating: { kind: rating }

The synth.R handed to a generator function is the record's own RNG, so a custom type stays deterministic under the seed and safe under parallel generation — draw from it rather than from math/rand, or you give up reproducibility.