Do not lint never-like enums

Author: Centri3

clippy_lints/src/incorrect_impls.rs

@@ -161,10 +161,8 @@ impl LateLintPass<'_> for IncorrectImpls {
                         // `MaybeUninit<T>`
                         ty::Adt(_, _) if is_type_lang_item(cx, ty, LangItem::MaybeUninit) => true,
                         // `[MaybeUninit<T>; N]`
-                        ty::Array(inner_ty, _) | ty::Slice(inner_ty)
-                            if is_type_lang_item(cx, *inner_ty, LangItem::MaybeUninit) =>
-                        {
-                            true
+                        ty::Array(inner_ty, _) | ty::Slice(inner_ty) => {
+                            is_type_lang_item(cx, *inner_ty, LangItem::MaybeUninit)
                         },
                         // Other cases are likely pretty rare.
                         _ => false,
@@ -174,6 +172,11 @@ impl LateLintPass<'_> for IncorrectImpls {
                 return;
             }
 
+            // Skip `never`-like enums
+            if def.is_enum() && def.variants().is_empty() {
+                return;
+            }
+
             if impl_item.ident.name == sym::clone {
                 if block.stmts.is_empty()
                     && let Some(expr) = block.expr

tests/ui/incorrect_clone_impl_on_copy_type.fixed

@@ -96,7 +96,8 @@ impl<A: Copy> Clone for Uwu<A> {
 
 impl<A: std::fmt::Debug + Copy + Clone> Copy for Uwu<A> {}
 
-// do not lint if type has only `MaybeUninit` fields
+// do not lint if type has only `MaybeUninit` fields, #11072
+
 struct G([std::mem::MaybeUninit<u32>; 100]);
 
 impl Clone for G {
@@ -106,3 +107,15 @@ impl Clone for G {
 }
 
 impl Copy for G {}
+
+// do not lint `never`-like enums, #11071
+
+enum H {}
+
+impl Clone for H {
+    fn clone(&self) -> Self {
+        todo!()
+    }
+}
+
+impl Copy for H {}

tests/ui/incorrect_clone_impl_on_copy_type.rs

@@ -106,7 +106,8 @@ impl<A: Copy> Clone for Uwu<A> {
 
 impl<A: std::fmt::Debug + Copy + Clone> Copy for Uwu<A> {}
 
-// do not lint if type has only `MaybeUninit` fields
+// do not lint if type has only `MaybeUninit` fields, #11072
+
 struct G([std::mem::MaybeUninit<u32>; 100]);
 
 impl Clone for G {
@@ -116,3 +117,15 @@ impl Clone for G {
 }
 
 impl Copy for G {}
+
+// do not lint `never`-like enums, #11071
+
+enum H {}
+
+impl Clone for H {
+    fn clone(&self) -> Self {
+        todo!()
+    }
+}
+
+impl Copy for H {}