use rustc_ast::tokenstream::TokenStream; use rustc_ast_pretty::pprust; use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult}; pub(crate) fn expand_log_syntax<'cx>( _cx: &'cx mut ExtCtxt<'_>, sp: rustc_span::Span, tts: TokenStream, ) -> MacroExpanderResult<'cx> { println!("{}", pprust::tts_to_string(&tts)); // any so that `log_syntax` can be invoked as an expression and item. ExpandResult::Ready(DummyResult::any_valid(sp)) }