From 4e92681aba42aa50a832ec3be547b31a9bbf20e1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lauren=C8=9Biu=20Nicola?= <lnicola@dend.ro>
Date: Mon, 25 Jan 2021 13:30:55 +0200
Subject: [PATCH] Disallow non-boolean literals in concat!

---
 crates/hir_expand/src/builtin_macro.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crates/hir_expand/src/builtin_macro.rs b/crates/hir_expand/src/builtin_macro.rs
index 2806842cddf..57bc6fbd787 100644
--- a/crates/hir_expand/src/builtin_macro.rs
+++ b/crates/hir_expand/src/builtin_macro.rs
@@ -331,7 +331,9 @@ fn concat_expand(
                 text.push_str(&component);
             }
             // handle boolean literals
-            tt::TokenTree::Leaf(tt::Leaf::Ident(id)) if i % 2 == 0 => {
+            tt::TokenTree::Leaf(tt::Leaf::Ident(id))
+                if i % 2 == 0 && (id.text == "true" || id.text == "false") =>
+            {
                 text.push_str(id.text.as_str());
             }
             tt::TokenTree::Leaf(tt::Leaf::Punct(punct)) if i % 2 == 1 && punct.char == ',' => (),
@@ -739,7 +741,7 @@ fn test_concat_expand() {
             r##"
             #[rustc_builtin_macro]
             macro_rules! concat {}
-            concat!("foo", r, 0, r#"bar"#, false);
+            concat!("foo", "r", 0, r#"bar"#, false);
             "##,
         );