delay expand macro bang when there has indeterminate path

compiler/rustc_builtin_macros/src/log_syntax.rs

@@ -1,14 +1,14 @@
 use rustc_ast::tokenstream::TokenStream;
 use rustc_ast_pretty::pprust;
-use rustc_expand::base;
+use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
 
 pub fn expand_log_syntax<'cx>(
-    _cx: &'cx mut base::ExtCtxt<'_>,
+    _cx: &'cx mut ExtCtxt<'_>,
     sp: rustc_span::Span,
     tts: TokenStream,
-) -> Box<dyn base::MacResult + 'cx> {
+) -> MacroExpanderResult<'cx> {
     println!("{}", pprust::tts_to_string(&tts));
 
     // any so that `log_syntax` can be invoked as an expression and item.
-    base::DummyResult::any_valid(sp)
+    ExpandResult::Ready(DummyResult::any_valid(sp))
 }