type.constructor_input

A type's constructor is given a value it can't convert, because the value is built on a different kind of value or may be none.

Area 2, Values and types; not declinable; the next step is usually the agent's.

Why Jadpo refuses it

A constructor, Type(value), builds a value of a type by checking every rule on it. It converts only between types built on the same kind of value, such as two types built on Uuid, so it can check the rules again without guessing how to change the value. Turning text into a UUID isn't a check, and Jadpo never casts.

What it looks like

main.jadpo:

type OrderId = Uuid {}type ProductName = Text {    max_length: 120}function order_for(name: ProductName) -> OrderId {    return OrderId(name)}

  |8 |     return OrderId(name)  |                    ^^^^ this is `ProductName`

(agent) at the end of the next: line means your coding agent can make the fix itself.

A value that may be none builds nothing either. Here maybe is a Count?, and a Quantity can't be none:

type Count = Int {    min: 0}type Quantity = Int {    min: 1    max: 1000}function quantity_of(maybe: Count?) -> Quantity {    return Quantity(maybe)}

   |11 |     return Quantity(maybe)   |                     ^^^^^ this is `Count?`

Handle the none case first with match. The value inside some(...) is a Count, built on Int as Quantity is, so a Quantity can be built from it.

How to fix it

If the function should start from another id, take a value built on Uuid, such as a CartId:

type CartId = Uuid {}function order_for(cart: CartId) -> OrderId {    return OrderId(cart)}

OrderId(cart) now converts one UUID-based type to another on purpose, and the two stay separate types everywhere else.

Related

• Creating values
• Named types
• Values that may be missing
• When one type can stand in for another