Auto merge of #76406 - GuillaumeGomez:create-e0774, r=pickfire,jyn514

Create E0774

2 files changed, 25 insertions, 0 deletions

diff --git a/compiler/rustc_error_codes/src/error_codes.rs b/compiler/rustc_error_codes/src/error_codes.rs
index 789a1fc35a6..b0be1bf7e72 100644
--- a/compiler/rustc_error_codes/src/error_codes.rs
+++ b/compiler/rustc_error_codes/src/error_codes.rs
@@ -455,6 +455,7 @@ E0769: include_str!("./error_codes/E0769.md"),
 E0770: include_str!("./error_codes/E0770.md"),
 E0771: include_str!("./error_codes/E0771.md"),
 E0773: include_str!("./error_codes/E0773.md"),
+E0774: include_str!("./error_codes/E0774.md"),
 ;
 //  E0006, // merged with E0005
 //  E0008, // cannot bind by-move into a pattern guard
diff --git a/compiler/rustc_error_codes/src/error_codes/E0774.md b/compiler/rustc_error_codes/src/error_codes/E0774.md
new file mode 100644
index 00000000000..79793ba9d7d
--- /dev/null
+++ b/compiler/rustc_error_codes/src/error_codes/E0774.md
@@ -0,0 +1,24 @@
+`derive` was applied on something which is not a struct, a union or an enum.
+
+Erroneous code example:
+
+```compile_fail,E0774
+trait Foo {
+    #[derive(Clone)] // error!
+    type Bar;
+}
+```
+
+As said above, the `derive` attribute is only allowed on structs, unions or
+enums:
+
+```
+#[derive(Clone)] // ok!
+struct Bar {
+    field: u32,
+}
+```
+
+You can find more information about `derive` in the [Rust Book].
+
+[Rust Book]: https://doc.rust-lang.org/book/appendix-03-derivable-traits.html