E1022

Ambiguous block expression. In MoonBit, the expression { value } is ambiguous because it could be interpreted as a block expression or a struct literal. For now, we treat it as a struct literal, but writing such expressions is discouraged.

Erroneous example

struct S {
  value : Int
}

fn main {
  let value = 3
  let s = { value }
  ignore(s)
}

Suggestion

If you want to construct a struct using the struct literal, you can add a comma to the end of the struct literal. Or you can call formatter on this buffer to have the comma added automatically.

fn main {
  let value = 3
  let s = { value, }
  ignore(s)
}

If you are using it as a block expression, please remove the braces as it has only one expression and is equivalent to the expression value:

fn main {
  let value = 3
  let s = value
  ignore(s)
}