macro_rules! emit_warning {
($span:expr, $($tts:tt)*) => { ... };
}
Emit an error while not aborting the proc-macro right away.
The emitted errors will be converted to a TokenStream
sequence
of compile_error!
invocations after the execution hits the end
of the function marked with [proc_macro_error]
.
Does nothing on stable
See the guide.