Macro diagnostic

macro_rules! diagnostic {
    ($fmt:literal $($arg:tt)*) => { ... };
    ($($key:ident = $value:expr,)+ $fmt:literal $($arg:tt)*) => { ... };
}

Construct a MietteDiagnostic in more user-friendly way.

Examples

use miette::{diagnostic, LabeledSpan, Severity};

let source = "(2 + 2".to_string();
let diag = diagnostic!(
    // Those fields are optional
    severity = Severity::Error,
    code = "expected::rparen",
    help = "always close your parens",
    labels = vec![LabeledSpan::at_offset(6, "here")],
    url = "https://example.com",
    // Rest of the arguments are passed to `format!`
    // to form diagnostic message
    "expected closing ')'",
);

Diagnostic without any fields:

let x = 1;
let y = 2;

 let diag = diagnostic!("{x} + {} = {z}", y, z = x + y);
assert_eq!(diag.message, "1 + 2 = 3");

let z = x + y;
let diag = diagnostic!("{x} + {y} = {z}");
assert_eq!(diag.message, "1 + 2 = 3");