Unified Errors, a non-proliferation treaty, and extensible types

language design
22

Alternative crazy idea I had:

pub fn run() -> Result<(), impl Error> {
  env_logger::init()?;
  let bytes = eat_bytes()?;
  info!("wow, bytes: {:?}", bytes);
  Ok(())
}

Where “impl Error” indicates a single concrete anonymous enum type with io::Error and SetLoggerError variants, which the compiler generates for you at compile time. It’s only as big as it has to be to accommodate the error types returned by run() (rather than every error type imported anywhere in the program), it has a statically known size, and it can be transparently replaced with a custom error type later on.

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