Function rustc_expand::base::check_zero_tts

pub fn check_zero_tts(cx: &ExtCtxt<'_>, span: Span, tts: TokenStream, name: &str)

Non-fatally assert that tts is empty. Note that this function returns even when tts is non-empty, macros that need to stop compilation should call cx.parse_sess.span_diagnostic.abort_if_errors() (this should be done as rarely as possible).