innpatron / smpl Goto Github PK

fn foo(s: { x: int, y: int, z: int}) -> int {
  return x + y + z;
}

// Current behavior (Covariant)
let bar: fn ({x: int, y: int}) -> int = foo;
bar(init {x: 1, y: 1});
// Invalid b/c foo expects x, y, and z

// Proposed behavior (Contravariant)
let baz: fn({x: int, y: int, z: int, w: int}) -> int = foo;
baz(init {x: 1, y: 1, z: 1, w: 1});
// Fine b/c w field will be discarded