Macro warning

macro_rules! warning {
    (
        $span:expr,
        $fmt:literal $(, $arg:expr)*
        $(; hint: $hint:literal $(, $hint_arg:expr)*)*
        $(,)?
    ) => { ... };
}

Construct a SourceDiagnostic with severity Warning.

You can also emit hints with the ; hint: "..." syntax.

warning!(span, "warning with a {}", "source result");
warning!(
    span, "warning with a {}", "source result";
    hint: "hint 1"
);
warning!(
    span, "warning with a {}", "source result";
    hint: "hint 1";
    hint: "hint 2";
);