[gcc r14-7809] gccrs: Add a test for malformed derive declaration input

[Arthur Cohen]

https://gcc.gnu.org/g:dbe2f8ad4dbaad9e6f718eca311cce5bffd02bc3

commit r14-7809-gdbe2f8ad4dbaad9e6f718eca311cce5bffd02bc3
Author: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>
Date:   Tue Jul 18 16:10:01 2023 +0200

    gccrs: Add a test for malformed derive declaration input
    
    Add a new test to highlight possible future regressions on malformed
    proc_macro_derive input.
    
    gcc/testsuite/ChangeLog:
    
            * rust/compile/proc_macro_derive_malformed.rs: New test.
    
    Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>

Diff:
---
 gcc/testsuite/rust/compile/proc_macro_derive_malformed.rs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/gcc/testsuite/rust/compile/proc_macro_derive_malformed.rs b/gcc/testsuite/rust/compile/proc_macro_derive_malformed.rs
new file mode 100644
index 00000000000..d83256b8a2e
--- /dev/null
+++ b/gcc/testsuite/rust/compile/proc_macro_derive_malformed.rs
@@ -0,0 +1,4 @@
+// { dg-additional-options "-frust-crate-type=proc-macro" }
+
+#[proc_macro_derive] // { dg-excess-errors "malformed 'proc_macro_derive' attribute input" }
+pub fn my_invalid_macro() {}