User error message

[cowboy8625]

I think using a crate for displaying error message to user makes sense as this VM will stay in Rust. The best looking one is ariadne and i have past experience using it. Worth noting that there is also codespan-reporting which used by nu-shell.

[cowboy8625]

Compile time errors seem straight forward in my mind.

Parser

• [ ] Add a new variant to the Expr enum in ast called Error(Span).

• [ ] In parser we would need to consume any errors till the matching ) then try to start parsing again.

• [ ] Accumulate all the Errors in parser then report then threw error diagnostic tool.

  Compiler

• [ ] On the Compiler struct we would need to add a Vec<Error> Error would need to hold any details of the error to report. This could be done threw a enum and different variants where the variants hold a Span.

• [ ] Recovering from an errors while compiling would be skipping to the next expression.

Going to keep editing this comment as I think of things to add.