E4197

Compiler diagnostic name: cannot_match_struct_constr.

A constructor declared by a struct is a constructor function, not a pattern constructor. It can be called to create a value, but it cannot be used in a match pattern.

Erroneous example

///|
priv struct Point {
  x : Int

  fn new(Int) -> Point
}

///|
fn Point::new(x : Int) -> Point {
  { x, }
}

///|
fn read(point : Point) -> Int {
  match point {
    Point(x) => x
  }
}

///|
test {
  let _ = read(Point(1))
}

Suggestion

Read the struct fields directly, or use another pattern that does not call the constructor function.

///|
priv struct Point {
  x : Int

  fn new(Int) -> Point
}

///|
fn Point::new(x : Int) -> Point {
  { x, }
}

///|
fn read(point : Point) -> Int {
  point.x
}

///|
test {
  inspect(read(Point(3)), content="3")
}