Explore surface syntax for records with optional fields.

[cristianoc]

Declaration

type t = { x: int, y?: string}

Access

let foo = (r:t) => switch r.y {
  | None => ""
  | Some(s) => s
}

Construction and update

let r = { x:3, y: "abc" }
let r2 = {...r, y: "def" }
let r3 = {...r, y: ?None }
let r4 = {...r, y: ?r2.y }

Pattern matching

switch r {
  | {y: "abc" } => "It is abc"
  | {y} => "It is something"
  | {y:?None} => "It is nothing"
}

Punning

let make1 = (~x, ~y} => {x; y}
let make2 = (~x, ?y, ()) => {x; ?y}
let isYSome = (r) => switch r {
  | {x:2, ?y} => y != None
  | _ => false
}

Currently uses @ns.optional which the type checker will need to learn about (knows @optional).

[mununki]

Fantastic work! 👍