E4158

Default implementation is required but not found.

When a trait declares that it has a default implementation, the implementation should exist.

错误示例

///|
pub(open) trait Close {
  // A default implementation is required but not found.
  close(Self) -> Unit raise = _
}

建议

从默认实现中移除类型参数：

///|
impl Close with close(_) {
  ()
}