codespan-derive

Derive macro for ergonomically creating a Diagnostic from an error macro

Usage

1. Add #[derive(IntoDiagnostic)] onto your error macro type.
2. Add a #[file_id(Type)] to signal what the FileId generic type of the Diagnostic will be.
3. Tag every variant with a #[message = ""] signalling what the error message should read.
4. Span-like values that implement IntoLabel can be tagged with #[primary] or #[secondary] to be marked in the generated error, with an optional message like #[primary = ""].

```rust

[derive(IntoDiagnostic)]

[file_id(SomeFileIdType)]

enum Error { #[message = "Compiler found the number {0} is too large"] NumberTooLarge(usize),

#[message = "Cannot parse string {string}"] BadString { string: String, #[primary = "The bad string appears here"] span: Span, }, } ```

Then handle it somewhere like:

```rust if let Some(err) = result { // IntoDiagnostic derived from macro let diagnostic = err.into_diagnostic();

// Basic codespan-diagnostic printing to terminal let writer = StandardStream::stderr(ColorChoice::Always); let config = codespan_reporting::term::Config::default(); term::emit(&mut writer.lock(), &config, &files, &diagnostic)?; } ```