From cdd317675179bf6849a526479dc91e41608d684b Mon Sep 17 00:00:00 2001
From: Piotr Figiela <77412592+Draggu@users.noreply.github.com>
Date: Tue, 21 Jan 2025 15:33:01 +0100
Subject: [PATCH] Emit error with derive on unsupported item (#7128)

---
 .../src/plugins/derive/mod.rs                  | 15 ++++++++++++++-
 crates/cairo-lang-plugins/src/test_data/derive | 18 +++++++++++++++---
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/crates/cairo-lang-plugins/src/plugins/derive/mod.rs b/crates/cairo-lang-plugins/src/plugins/derive/mod.rs
index bc4bf8ee14d..5a2f288d077 100644
--- a/crates/cairo-lang-plugins/src/plugins/derive/mod.rs
+++ b/crates/cairo-lang-plugins/src/plugins/derive/mod.rs
@@ -58,7 +58,20 @@ impl MacroPlugin for DerivePlugin {
                 extern_type_ast.generic_params(db),
                 TypeVariantInfo::Extern,
             ),
-            _ => return PluginResult::default(),
+            _ => {
+                let maybe_error = item_ast.find_attr(db, DERIVE_ATTR).map(|derive_attr| {
+                    vec![PluginDiagnostic::error(
+                        derive_attr.as_syntax_node().stable_ptr(),
+                        "`derive` may only be applied to `struct`s, `enum`s and `extern type`s"
+                            .to_string(),
+                    )]
+                });
+
+                return PluginResult {
+                    diagnostics: maybe_error.unwrap_or_default(),
+                    ..PluginResult::default()
+                };
+            }
         })
     }
 
diff --git a/crates/cairo-lang-plugins/src/test_data/derive b/crates/cairo-lang-plugins/src/test_data/derive
index c3e1a36cd83..16f10f7ea91 100644
--- a/crates/cairo-lang-plugins/src/test_data/derive
+++ b/crates/cairo-lang-plugins/src/test_data/derive
@@ -411,6 +411,9 @@ struct UnsupportedTrait {}
 #[derive(long::path)]
 struct NonSimplePath {}
 
+#[derive(Copy, Debug, Destruct, PanicDestruct, Default, Hash)]
+fn unsupportedItem() {}
+
 #[derive(Clone)]
 extern type NotCloneable;
 
@@ -441,6 +444,9 @@ struct UnsupportedTrait {}
 #[derive(long::path)]
 struct NonSimplePath {}
 
+#[derive(Copy, Debug, Destruct, PanicDestruct, Default, Hash)]
+fn unsupportedItem() {}
+
 #[derive(Clone)]
 extern type NotCloneable;
 
@@ -488,19 +494,25 @@ error: Unknown derive `long::path` - a plugin might be missing.
          ^^^^^^^^^^
 
 
+error: `derive` may only be applied to `struct`s, `enum`s and `extern type`s
+ --> test_src/lib.cairo:13:1
+#[derive(Copy, Debug, Destruct, PanicDestruct, Default, Hash)]
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+
 error: Unsupported trait for derive for extern types.
- --> test_src/lib.cairo:13:10
+ --> test_src/lib.cairo:16:10
 #[derive(Clone)]
          ^^^^^
 
 
 error: derive `Default` for enum only supported with a default variant.
- --> test_src/lib.cairo:16:10
+ --> test_src/lib.cairo:19:10
 #[derive(Default)]
          ^^^^^^^
 
 
 error: Multiple variants annotated with `#[default]`
- --> test_src/lib.cairo:26:5
+ --> test_src/lib.cairo:29:5
     #[default]
     ^^^^^^^^^^