Document Subtyping / Structural Typing / Type Coercion Operator (:>)

[ryyppy]

ReScript is internally using the object system within Js.t to allow structural typing.

e.g.

type user = { "name": string }

is expressed as Js.t < name : string >. This is kinda an implementation detail, but there are scenarios where you can use the :> operator to coerce between different object shapes explicitly.

e.g. x :> { . }

In ReScript lingo, we call Js.t<...> types Objects. Our current docs are covered in the Objects docs. Not sure if subtyping should be an advanced section here.

[ryyppy]

Update: Js.t got irrelevant with v9.1... so the docs will be even simpler.