Macro fa_compile_error 

macro_rules! fa_compile_error {
    (
        code = $code:expr,
        message = $msg:expr
        $(, help = $help:expr)?
    ) => { ... };
}

Compile-time diagnostic error.

This produces a hard compiler error with a formatted message.

Example

fa_compile_error!(
    code = "FA101",
    message = "Bevy support enabled but plugin not registered",
    help = "add .add_plugins(SmartAllocPlugin) to your App"
);