[gcc/devel/rust/master] testsuite/rust: add a testcase for testing ...

[Thomas Schwinge <tschwinge@gcc.gnu.org>]

https://gcc.gnu.org/g:1c19256b70634ab62eeddefed58556bfc4912a90

commit 1c19256b70634ab62eeddefed58556bfc4912a90
Author: liushuyu <liushuyu011@gmail.com>
Date:   Mon Sep 26 22:30:33 2022 -0600

    testsuite/rust: add a testcase for testing ...
    
    ... builtin macro and decl macro mixed expansion

Diff:
---
 gcc/testsuite/rust/compile/builtin_macro_recurse.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/gcc/testsuite/rust/compile/builtin_macro_recurse.rs b/gcc/testsuite/rust/compile/builtin_macro_recurse.rs
new file mode 100644
index 00000000000..0b516fd93a9
--- /dev/null
+++ b/gcc/testsuite/rust/compile/builtin_macro_recurse.rs
@@ -0,0 +1,21 @@
+// { dg-additional-options "-fdump-tree-gimple" }
+
+#[rustc_builtin_macro]
+macro_rules! concat {
+    () => {{}};
+}
+
+macro_rules! a {
+    () => { "test" };
+}
+
+macro_rules! b {
+    () => { "canary" };
+}
+
+fn main() {
+    // { dg-final { scan-tree-dump-times {"test1canary"} 1 gimple } }
+    let _ = concat!(a!(), 1, b!());
+    // should not error
+    concat!(a!(), true, b!(),);
+}