Simplify all Error handling if all errors implement Show

[gmlewis]

Currently, Error represents an error where no information can be extracted from it unless it is pattern-matched explicitly against a known collection of possible errors. (Please correct me if I'm wrong.)

What if Error and all custom error types created by type! were forced to provide a to_string method so that no matter what kind of error happens, information can be shown to the user about the specific error?

Wouldn't this dramatically simplify all error handling by enabling all functions that might error to simply return T!Error and then at some point up the call chain the error can be handled and to_string() can be called to report the error?

[gmlewis]

@peter-jerry-ye - while working on supporting MoonBit in Modus:
gmlewis/modus#1
this is becoming increasingly important.

For example, in auto-generated code, if all errors have a to_string() method, then they can very easily be sent back to the host.
Otherwise, it is an extremely difficult task to try and figure out all the possible errors that might be raised and account for each and every one.

Thoughts?

EDIT: It is now working - see below.

[gmlewis]

Actually, I just now tried it out again, and suddenly it is working with this version of the compiler:

$ moon version --all
moon 0.1.20250107 (099c4c7 2025-01-07) ~/.moon/bin/moon
moonc v0.1.20250108+7a6b9ab0e ~/.moon/bin/moonc
moonrun 0.1.20250107 (099c4c7 2025-01-07) ~/.moon/bin/moonrun

so please feel free to close this discussion.