1 files changed, 38 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/invalid_derive_target.rs b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/invalid_derive_target.rs
new file mode 100644
index 000000000..c779266bc
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide-diagnostics/src/handlers/invalid_derive_target.rs
@@ -0,0 +1,38 @@
+use crate::{Diagnostic, DiagnosticsContext, Severity};
+
+// Diagnostic: invalid-derive-target
+//
+// This diagnostic is shown when the derive attribute is used on an item other than a `struct`,
+// `enum` or `union`.
+pub(crate) fn invalid_derive_target(
+    ctx: &DiagnosticsContext<'_>,
+    d: &hir::InvalidDeriveTarget,
+) -> Diagnostic {
+    let display_range = ctx.sema.diagnostics_display_range(d.node.clone()).range;
+
+    Diagnostic::new(
+        "invalid-derive-target",
+        "`derive` may only be applied to `struct`s, `enum`s and `union`s",
+        display_range,
+    )
+    .severity(Severity::Error)
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_diagnostics;
+
+    #[test]
+    fn fails_on_function() {
+        check_diagnostics(
+            r#"
+//- minicore:derive
+mod __ {
+    #[derive()]
+  //^^^^^^^^^^^ error: `derive` may only be applied to `struct`s, `enum`s and `union`s
+    fn main() {}
+}
+            "#,
+        );
+    }
+}