Difficulties with generic serialisable type about io-ts HOT 2 CLOSED

After a sleep I realise I am being dumb here.

io-ts runtime types may be isomorphic to compile-time types but they do not themselves obey a covariant runtime hierarchy over the schemas.

exit stage left

from io-ts.

Well in case anyone else finds themselves in a similar quagmire the 'solution' is to use the compile-time A, O, I types directly in the dependent classes like:

export class Extractor<
  Scope,
  ScopeO extends Json,
  Output,
  OutputO extends Json,
>

Then reference them in the schema types like t.Type<Scope, ScopeO> etc

from io-ts.