Basic Creating and Composing

You can create "non discriminated" errors using the types provided by Ferrum.

To create an error that contains only message, use MessageError:

IError error = new MessageError("Message based error");

Debug.Assert(error.Message == "Message based error");
Debug.Assert(error.InnerError == null);

Add high-level context to errors to understand where and how low-level errors happen. Use ContextError class or error.Context(string) extension:

IError cause = new MessageError("Main error");
IError error = new ContextError("Context error", cause);

Debug.Assert(error.Message == "Context error");
Debug.Assert(error.InnerError!.Message == "Main error");

All types that are errors could implement IError, but this is not always possible. AnyError.OfValue converts any type to an IError. By default, the result of ToString is used for the error message, but some types converted in a more idiomatic way. You should not depend on the specific behavior of AnyError.OfValue.

(string, int, int) notIErrorError = ("invalid token", 12, 48);
IError error = AnyError.OfValue(notIErrorError);

Assert.Equal("(invalid token, 12, 48)", error.Message);

The error.Chain() extension gets the entire chain of errors as an enumerator, and error.GetRoot() gets the root error (the last error in the chain).