Macro error

macro_rules! error {
    ($fmt:literal $(, $arg:expr)* $(,)?) => { ... };
    (
        $fmt:literal $(, $arg:expr)*
        $(; hint: $hint:literal $(, $hint_arg:expr)*)*
        $(,)?
    ) => { ... };
    (
        $span:expr, $fmt:literal $(, $arg:expr)*
        $(; label_message: $label_message:literal $(, $label_message_arg:expr)*)?
        $(; label: $label:expr)*
        $(; fix: $fix:expr)*
        $(; note: $note:literal $(, $note_arg:expr)*)*
        $(; hint: $hint:literal $(, $hint_arg:expr)*)*
        $(; code: $code:expr)?
        $(,)?
        $(;)?
    ) => { ... };
}

Construct an EcoString, [HintedString] or SourceDiagnostic with severity Error.