Fix deriving ZeroizeOnDrop on items with generics (#787)

Author: daxpedda

zeroize/derive/src/lib.rs

@@ -71,7 +71,7 @@ fn derive_zeroize(mut s: synstructure::Structure<'_>) -> TokenStream {
 fn derive_zeroize_on_drop(mut s: synstructure::Structure<'_>) -> TokenStream {
     let zeroizers = generate_fields(&mut s, quote! { zeroize_or_on_drop });
 
-    let drop_impl = s.gen_impl(quote! {
+    let drop_impl = s.add_bounds(AddBounds::None).gen_impl(quote! {
         gen impl Drop for @Self {
             fn drop(&mut self) {
                 use zeroize::__internal::AssertZeroize;

zeroize/tests/zeroize_derive.rs

@@ -315,3 +315,13 @@ fn derive_deref() {
     }
     assert_eq!(&value.0 .0, &[0, 0, 0])
 }
+
+#[test]
+#[cfg(feature = "alloc")]
+fn derive_zeroize_on_drop_generic() {
+    #[derive(ZeroizeOnDrop)]
+    struct Y<T: Zeroize>(Box<T>);
+
+    #[derive(ZeroizeOnDrop)]
+    struct Z<T: Zeroize>(Vec<T>);
+}