Fix: Empty enum never type suggested only if the feature is enabled

clippy_lints/src/empty_enum.rs

@@ -8,6 +8,10 @@ use rustc_session::{declare_lint_pass, declare_tool_lint};
 declare_clippy_lint! {
  /// **What it does:** Checks for `enum`s with no variants.
  ///
+ /// As of this writing, the never type is still a
+ /// nightly-only experimental API. Therefore, this lint is only triggered
+ /// if the never type is enabled
+ ///
  /// **Why is this bad?** If you want to introduce a type which
  /// can't be instantiated, you should use `!` (the never type),
  /// or a wrapper around it, because `!` has more extensive
@@ -44,7 +48,9 @@ impl<'tcx> LateLintPass<'tcx> for EmptyEnum {
  if let ItemKind::Enum(..) = item.kind {
  let ty = cx.tcx.type_of(did);
  let adt = ty.ty_adt_def().expect("already checked whether this is an enum");
- if adt.variants.is_empty() {
+
+ // Only suggest the never type if the feature is enabled
+ if adt.variants.is_empty() && cx.tcx.features().never_type {
  span_lint_and_help(
  cx,
  EMPTY_ENUM,

tests/ui/empty_enum.rs

@@ -1,6 +1,7 @@
 #![allow(dead_code)]
 #![warn(clippy::empty_enum)]
-
+// Enable never type to test empty enum lint
+#![feature(never_type)]
 enum Empty {}
 
 fn main() {}

tests/ui/empty_enum.stderr

@@ -1,5 +1,5 @@
 error: enum with no variants
- --> $DIR/empty_enum.rs:4:1
+ --> $DIR/empty_enum.rs:5:1
  |
 LL | enum Empty {}
  | ^^^^^^^^^^^^^