===== AST after reference-resolving =====
SystemUTCEpochMilliseconds():
TreeList
  BinaryOperation Assignment
    Var global
    FunctionCall
      UnresolvedReference GetGlobalObject
  BinaryOperation Assignment
    Var nowNs
    FunctionCall
      UnresolvedReference HostSystemUTCEpochNanoseconds
      Var global
  ReturnNode
    FunctionCall
      UnresolvedReference 𝔽
      FunctionCall
        UnresolvedReference floor
        BinaryOperation Division
          Var nowNs
          MathematicalConstant 1000000