From 9a320bcf3870416c9b01ccf6bcedb73fdfdd93db Mon Sep 17 00:00:00 2001
From: Jonas Schievink <jonasschievink@gmail.com>
Date: Thu, 9 Sep 2021 21:32:41 +0200
Subject: [PATCH] Support the new `rustc_builtin_macro` syntax

---
 crates/hir_def/src/nameres/collector.rs | 15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/crates/hir_def/src/nameres/collector.rs b/crates/hir_def/src/nameres/collector.rs
index 165cdcba00c..24083172b30 100644
--- a/crates/hir_def/src/nameres/collector.rs
+++ b/crates/hir_def/src/nameres/collector.rs
@@ -1812,7 +1812,20 @@ impl ModCollector<'_, '_> {
                     name = tt::Ident { text: it.clone(), id: tt::TokenId::unspecified() }.as_name();
                     &name
                 }
-                None => &mac.name,
+                None => {
+                    match attrs.by_key("rustc_builtin_macro").tt_values().next().and_then(|tt| {
+                        match tt.token_trees.first() {
+                            Some(tt::TokenTree::Leaf(tt::Leaf::Ident(name))) => Some(name),
+                            _ => None,
+                        }
+                    }) {
+                        Some(ident) => {
+                            name = ident.as_name();
+                            &name
+                        }
+                        None => &mac.name,
+                    }
+                }
             };
             let krate = self.def_collector.def_map.krate;
             match find_builtin_macro(name, krate, ast_id) {