E4113

E4113#

Constructor has no field with the given name.

This error occurs when trying to access a field that doesn’t exist in a constructor pattern. In MoonBit, when pattern matching with constructors that have named fields, you can only access fields that were defined in the constructor’s declaration.

This commonly happens when:

  • Misspelling a field name

  • Trying to access a field that exists in a different constructor

  • Trying to access a field that was removed or renamed in the type definition

错误示例#

pub enum E {
  A(a~: Int)
}

pub fn f(x: E) -> Unit {
  match x {
    A(..) as a => {
      println(a.a)
      println(a.b)
//            ^^^ Error: Constructor A of type E has no field b.
    }
  }
}

建议#

To fix this error, you can either:

  • add the missing field to the constructor

pub enum E {
  A(a~: Int, b~: Bool)
}

pub fn f(x: E) -> Unit {
  match x {
    A(..) as a => {
      println(a.a)
      println(a.b)
    }
  }
}

  • remove the incorrect field access

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