fix(empty_enum): don't lint if all variants happen to be cfg-d out

Author: ada4a

clippy_lints/src/empty_enum.rs

@@ -1,4 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::span_contains_cfg;
 use rustc_hir::{Item, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
@@ -25,10 +26,6 @@ declare_clippy_lint! {
     ///   matched to mark code unreachable. If the field is not visible, then the struct
     ///   acts like any other struct with private fields.
     ///
-    /// * If the enum has no variants only because all variants happen to be
-    ///   [disabled by conditional compilation][cfg], then it would be appropriate
-    ///   to allow the lint, with `#[allow(empty_enum)]`.
-    ///
     /// For further information, visit
     /// [the never type’s documentation][`!`].
     ///
@@ -66,6 +63,7 @@ impl LateLintPass<'_> for EmptyEnum {
             && def.variants.is_empty()
             // Only suggest the `never_type` if the feature is enabled
             && cx.tcx.features().never_type()
+            && !span_contains_cfg(cx, item.span)
         {
             span_lint_and_help(
                 cx,

tests/ui/empty_enum.rs

@@ -5,4 +5,21 @@
 enum Empty {}
 //~^ empty_enum
 
+mod issue15910 {
+    enum NotReallyEmpty {
+        #[cfg(false)]
+        Hidden,
+    }
+
+    enum OneVisibleVariant {
+        #[cfg(false)]
+        Hidden,
+        Visible,
+    }
+
+    enum CfgInsideVariant {
+        Variant(#[cfg(false)] String),
+    }
+}
+
 fn main() {}