Make tests actually make sense

tests/structs/src/debug_derive.c

@@ -0,0 +1,29 @@
+//! derive:Debug
+
+#include <stdarg.h>
+
+typedef struct {
+    int a;
+} Debuggable1;
+
+typedef struct {
+    va_list v;
+} Debuggable2;
+
+Debuggable1 *kDebuggable1;
+Debuggable2 *kDebuggable2;
+
+// A struct containing a union cannot derive Debug, so make
+// sure we don't generate a #[derive] for it
+typedef struct {
+    struct {
+        struct {
+            union {
+                int d;
+                float e;
+            } c;
+        } b;
+    } a;
+} NotDebuggable1;
+
+NotDebuggable1 kNotDebuggable1;

tests/structs/src/test_debug_derive.rs

@@ -0,0 +1,11 @@
+//! feature_c_variadic
+
+use crate::debug_derive::{rust_kDebuggable1, rust_kDebuggable2};
+use std::fmt::Debug;
+
+pub fn test_debuggable() {
+    unsafe {
+        // Make sure all debuggable structs implement `Debug`
+        let _debuggable: Vec<*mut dyn Debug> = vec![rust_kDebuggable1, rust_kDebuggable2];
+    }
+}