E4109

Return must be inside a function.

This error occurs when a return statement is used outside of a function. In MoonBit, return statements must be inside a function body.

错误示例

pub let x: Int = { return 42 }
//                 ^^^^^^^^^ Error: Return must be inside a function.
pub let y: Int = {
  if x == 42 {
    x + 1
  } else {
    return 0
//  ^^^^^^^^ Error: Return must be inside a function.
  }
}

建议

To fix this error, you can remove the return statement from the let binding:

pub let x: Int = 42
pub let y: Int = {
  if x == 42 {
    x + 1
  } else {
    0
  }
}