compile_msg

A syntax extension for emitting messages at compile time, via the compiler, similar to #warning and #error in the C preprocessor. Four macros are provided (in order of increasing severity):

• compile_note: tell the user a tidbit of information without implying it is a problem,
• compile_warning: tell the user that something could go wrong,
• compile_error: tell the user about some error, compilation will not stop immediately, but will halt before any compiler passes after macro expansion.
• compile_fatal: tell the user about a catastrophic error and immediately halt compilation. compile_error is strongly preferred as it allows further errors and warnings to be picked up in a single pass.

The macros can be placed as an item (expanding to nothing), and as an expression (expanding to a literal unit, i.e. ()). They are best used in conditionally compiled items, e.g. if a certain operating system is entirely unsupported, one can use compile_error! with an appropriate #[cfg] attribute.

Usage

Ensure your Cargo.toml contains

toml [dependencies.compile_msg] git = "https://github.com/huonw/compile_msg"

and then load the syntax in the normal manner:

```rust

![feature(phase)]

[phase(plugin)] extern crate compile_msg;

[cfg(target_os = "hal")]

compile_error!("I'm sorry, Dave, I'm afraid I can't do that.")

fn main() { compile_note!("please be careful"); // note: please be careful

compile_warning!("take more care"); // warning: take more care


compile_error!("things are breaking"); // error: things are breaking


compile_fatal!("catastrophic failure!"); // error: catastrophic failure
// (compilation stops here)


compile_warning!("not emitted");

} ```

(If that compiled, it would be equivalent to fn main() {} at runtime.)