E4136

This expression has type that is not a newtype.

In MoonBit, you can access the field of underlying struct of a newtype by using the dot access operator (.). However, you cannot access the field of a struct if it is not wrapped in a newtype.

错误示例

struct Inner {
  value : Int
}

type! ErrorOuter Inner

enum EnumOuter {
  Outer(Inner)
}

fn main {
  let outer : ErrorOuter = ErrorOuter(Inner::{ value: 1 })
  println(outer.value) // Error: This expression has type ErrorOuter, which is a error type type and not a record.
  let outer : EnumOuter = Outer(Inner::{ value: 2 })
  println(outer.value) // Error: This expression has type EnumOuter, which is a variant type and not a record.
}

建议

If you want to access the field of the underlying struct, you should wrap the in a newtype:

type Outer Inner

fn main {
  let outer : Outer = Inner::{ value: 1 }
  println(outer.value)
}