Allow Some Polymorphism for Records

[keyan-m]

What are Constrained Polymorphic Records?

Inspired by "extensible records" in Elm programming language, a record type that is constrained to having a set of specific fields, while free to have arbitrary fields otherwise, can be defined as a constrained polymorphic record.

What is the advantage?

Allows for defining more abstract functions, which can potentially pave the way for having more developer-friendly packages with minimal overhead.

A sample use case can be:

fn validate_output(
  datum: Datum,
  redeemer: { a | output_index: Int },
  ctx: ScriptContext,
) -> Bool {
  // Use `output_index` to pick the continued UTxO.
  // This helper function can be used for any `redeemer` as
  // long as it is a record type (i.e. single constructor)
  // with an `output_index` field with type `Int`.
}

How can this be accomplished?

As pointed out by @rvcas, order of values matter in UPLC, therefore this may not be a trivial feature to add. However, at this stage it's probably best to first discuss whether this is desirable in the first place, and what are its pros/cons.