Add error when proc_macro_derive is used not on functions

Fixes #37590

1 files changed, 6 insertions, 0 deletions

diff --git a/src/test/compile-fail-fulldeps/proc-macro/require-rustc-macro-crate-type.rs b/src/test/compile-fail-fulldeps/proc-macro/illegal-proc-macro-derive-use.rs
index 44397cdde0c..405994b36e2 100644
--- a/src/test/compile-fail-fulldeps/proc-macro/require-rustc-macro-crate-type.rs
+++ b/src/test/compile-fail-fulldeps/proc-macro/illegal-proc-macro-derive-use.rs
@@ -18,4 +18,10 @@ pub fn foo(a: proc_macro::TokenStream) -> proc_macro::TokenStream {
     a
 }
 
+// Issue #37590
+#[proc_macro_derive(Foo)]
+//~^ ERROR: the `#[proc_macro_derive]` attribute may only be used on bare functions
+pub struct Foo {
+}
+
 fn main() {}