Constrained monomorph vs const struct

[kLabz]

class Test4 {
  static function main() {
    var data = [
      {name: 'Page A', uv: 4000, pv: 2400, amt: 2400},
      {name: 'Page B', uv: 3000, pv: 1398, amt: 2210},
      {name: 'Page C', uv: -1000, pv: 9800, amt: 2290},
      {name: 'Page D', uv: 500, pv: 3908, amt: 2000},
      {name: 'Page E', uv: -2000, pv: 4800, amt: 2181},
      {name: 'Page F', uv: -250, pv: 3800, amt: 2500},
      {name: 'Page G', uv: 3490, pv: 4300, amt: 2100}
    ];

    foo(data);
  }

  static function foo<T:{uv:Int}>(data:Array<T>):Void {}
}

/*
  Test4.hx:13: characters 7-11 : error: { uv : Int, pv : Int, name : String, amt : Int } has extra field amt
  Test4.hx:13: characters 7-11 :  have: Array<{ uv, pv, name, amt }>
  Test4.hx:13: characters 7-11 :  want: Array<{ uv }>
  Test4.hx:13: characters 7-11 : For function argument 'data'
*/

[Simn]

This is a variant of #3192. It used to work just because constraints checks were delayed until after the Const flag was removed via ctx.opened in type_function. With the checks being done earlier now, the flag is still set by the time we unify.

[kLabz]

Workaround:

static function foo<TBase:{uv:Int}, T:TBase>(data:Array<T>):Void {}