E4101

Unsupported expression after the pipe operator.

This error occurs when the expression after the pipe operator (|>) is not in a supported form. The pipe operator allows you to chain function calls in a more readable way, but only supports specific forms on its right-hand side.

The following forms are allowed after the pipe operator:

1. A single identifier (function name)

2. A regular function application (but not method calls)

3. A constructor name

4. A constructor application

错误示例

type T Int

fn m(self: T, x: Int) -> Unit {
  println(self._ + x)
}

pub fn f(t: T, x: Int) -> Unit {
  x |> fn(x: Int) { println(x)}
//     ^^^^^^^^^^^^^^^^^^^^^^^^ Error: Unsupported expression after the pipe operator.
  x |> t.m()
//     ^^^^ Error: Unsupported expression after the pipe operator.
}

建议

To fix this error, you can change the invalid pipe expression to normal function or method application.

type T Int

fn m(self: T, x: Int) -> Unit {
  println(self._ + x)
}

pub fn f(t: T, x: Int) -> Unit {
  fn(x: Int) { println(x)}(x)
  t.m(x)
}