# tracing::warn - Rust
API documentation for the Rust `warn` macro in crate `tracing`.
Keywords: rust, rustlang, rust-lang, warn

# Macro tracing::warn [−] [src]

    macro_rules! warn {
        (target: $target:expr, parent: $parent:expr, { $($field:tt)* }, $($arg:tt)* ) => { ... };
        (target: $target:expr, parent: $parent:expr, $($k:ident).+ $($field:tt)+ ) => { ... };
        (target: $target:expr, parent: $parent:expr, ?$($k:ident).+ $($field:tt)+ ) => { ... };
        (target: $target:expr, parent: $parent:expr, %$($k:ident).+ $($field:tt)+ ) => { ... };
        (target: $target:expr, parent: $parent:expr, $($arg:tt)+ ) => { ... };
        (parent: $parent:expr, { $($field:tt)+ }, $($arg:tt)+ ) => { ... };
        (parent: $parent:expr, $($k:ident).+ = $($field:tt)*) => { ... };
        (parent: $parent:expr, ?$($k:ident).+ = $($field:tt)*) => { ... };
        (parent: $parent:expr, %$($k:ident).+ = $($field:tt)*) => { ... };
        (parent: $parent:expr, $($k:ident).+, $($field:tt)*) => { ... };
        (parent: $parent:expr, ?$($k:ident).+, $($field:tt)*) => { ... };
        (parent: $parent:expr, %$($k:ident).+, $($field:tt)*) => { ... };
        (parent: $parent:expr, $($arg:tt)+) => { ... };
        (target: $target:expr, { $($field:tt)* }, $($arg:tt)* ) => { ... };
        (target: $target:expr, $($k:ident).+ $($field:tt)* ) => { ... };
        (target: $target:expr, ?$($k:ident).+ $($field:tt)* ) => { ... };
        (target: $target:expr, %$($k:ident).+ $($field:tt)* ) => { ... };
        (target: $target:expr, $($arg:tt)+ ) => { ... };
        ({ $($field:tt)+ }, $($arg:tt)+ ) => { ... };
        ($($k:ident).+ = $($field:tt)*) => { ... };
        (?$($k:ident).+ = $($field:tt)*) => { ... };
        (%$($k:ident).+ = $($field:tt)*) => { ... };
        ($($k:ident).+, $($field:tt)*) => { ... };
        (?$($k:ident).+, $($field:tt)*) => { ... };
        (%$($k:ident).+, $($field:tt)*) => { ... };
        (?$($k:ident).+) => { ... };
        (%$($k:ident).+) => { ... };
        ($($k:ident).+) => { ... };
        ($($arg:tt)+) => { ... };
    }

Constructs an event at the warn level.

This functions similarly to the `event!` macro. See the top-level documentation for details on the syntax accepted by this macro.

# Examples

    use tracing::warn;

    let warn_description = "Invalid Input";
    let input = &[0x27, 0x45];

    warn!(?input, warning = warn_description);
    warn!(
        target: "input_events",
        warning = warn_description,
        "Received warning for input: {:?}", input,
    );